OK. Still having fuel issue.. 92 caprice 350 non-police 5.0L Replaced fuel filter, fuel pump, disconnected 2 fuel lines at throttle body and gas is getting to that point within the proper psi (had someone check with gauges). Fuel pump fuse is not blown, the 2 relays on passenger side under hood are good (pump and pulser I believe).

Original post: http://www.automotiveforums.com/vbulletin/showthread.php?p=4243217#post4243217

CODE 23 _Cleared_

NO current codes (just the 12).

Turning the car over gets NO gas to the injectors in the throttle body.

Pouring gas into the TB allows the car to crank and the gas flows free and steady from the 2 injectors.. and will continue to do so above idle, but when allowed back to idle, the car dies and no longer will crank without adding fuel to TB.

I've read a LOT: http://www.chevythunder.com/fuel%20injection%20troubleshooting%20pg%20a.htm#Er asing%20trouble%20codes has trouble shooting.. and http://www.chevythunder.com/gm_throttle_body_injection_pg_1.htm has the TB help.

PLEASE advise what else to check (from reading it tells me the IAC valve possibly, shrug).

I'm stuck and need your guys' expert advise. I'm just a regular guy with no mechanical experience that has managed to learn a LOT from this forum ( I replaced my starter, fixed coolant issues and the above with your help) and appreciate the learning experience greatly. It's been fun up until this point, and I'm trying my best not to give up and get discouraged. And also, I can't afford to have it towed to a shop at this point.

If there's any info I've left out, please ask.. and thanks to any and all for any advise or opinions, however small or insignificant to you, will surely help me tremendously!! :)

OK, now that you have checked all of that...

On TBI cars there is an oil pressure switch. It check to make sure the engine has enough oil pressure before allowing the injectors to fire. Sounds like this is the last thing for you to check. Since I'm guessing your car does not have an oil pressure gauge, check the voltage, while cranking, across the oil pressure sender, located at the back of the intake manifold.

Can anyone supply a picture for this?

Do you have access to a scanner to read engine data?

I haven't checked the oil pressure with a device, but at the start I read that info and checked with dipstick and added almost a quart to get it completely full.. but in the past I've been more than a quart low at times..

I do not have access to a scanner, I just used the paper clip method to get the codes, but I'm sure you must be referring to a more detailed analysis..

It's just frustrating that the gas is getting right there to the throttle body.. but won't shoot out while cranking.. weird.

Thanks for replying :)

Keep it coming please.. don't give up on me yet.. I won't!! I'll stay until it is running and post results and many thanks..

What CD is getting at is that the switch (oil pressure switch) might be defective, or it might be unplugged, or a wire may be chaffed/cut/stretched etc.

The oil pressure switch is generally located on the back of the block, on the rear intake seal area just to the right of, and under, the distributor. It's vertically oriented. Note - It won't be under the distributor if you have a small-cap distributor (which you should). An alternate location might be on the block, driver side, above the oil filter - horizontally oriented.

The purpose of the fuel-pump interlock is to shut off the fuel pump in the event of an accident/rollover etc - by blocking power flow to the fuel pump when the engine is off (no oil pressure). If the switch is bad or other wiring faults as noted above, the engine could look "off" to the circuit, preventing the pump from working.

There should be three wires on the switch - one of these is the interlock.

Oh, I see! :)

See how us non-mechanically inclined aren't thinking sometimes on the same wavelenght.. :P

It's 3am here now, will check that tommorow afternoon and get back on and post results..

Thanks for clearing that up for me!! :D

See you tomorrow..

Was wondering:

If the oil pressure switch is bad, when we disconnected the 2 fuel lines from the TBI, shouldn't there have been no gas coming out if the switch was telling the pump to not pump? And remember it will run when primed with gas until it drops down to idle.. be back tomorrow with more results and questions.. :)

Upon checking Autozone's site, I was in error I see. My dad said it was a 350.. turns out it is the:

8 Cylinder 305 E 5.0L TBI

.. if that makes any difference with anything I've posted..

Doesn't make any difference.

Was wondering:

If the oil pressure switch is bad, when we disconnected the 2 fuel lines from the TBI, shouldn't there have been no gas coming out if the switch was telling the pump to not pump? And remember it will run when primed with gas until it drops down to idle.. be back tomorrow with more results and questions.. :)

No this switch simply prevents the injectors from firing. It does not control the fuel pump at all.

I was told elsewhere on the forum that the oil pressure switch only continued fuel flow if the fuel pump relay went out. This may only apply to newer engines, but worth a check. Shouldn't you be able to ground the wire going to the oil switch and bypass it to see if the injectors will fire on their own?

I was told elsewhere on the forum that the oil pressure switch only continued fuel flow if the fuel pump relay went out. This may only apply to newer engines, but worth a check. Shouldn't you be able to ground the wire going to the oil switch and bypass it to see if the injectors will fire on their own?

No, the pressure switch does just what CD and silicon212 said. It will cut off flow if sufficient oil pressure does not build a few seconds after cranking.

I see. I guess diff. years and models have diff. ways.

OK..

Don't know where the oil pressure switch is..

Found a vacuum leak.. the line that goes into the big horn-looking thing on the back side of the TB.. it also goes to 3 other places.. fixed the leak.

Still needs priming to start, but made it to the corner store and back (died 3 times)..

Now there is a CODE 33. MAP.

Would a bad map cause these problems? And if so, why the heck did it JUST NOW start coding - after replacing the vacuum leak...??

I think I may set this mutha on fire!!!

:banghead:

Thanks for hanging in there with me...

OK..

Don't know where the oil pressure switch is..

Found a vacuum leak.. the line that goes into the big horn-looking thing on the back side of the TB.. it also goes to 3 other places.. fixed the leak.

Still needs priming to start, but made it to the corner store and back (died 3 times)..

Now there is a CODE 33. MAP.

Would a bad map cause these problems? And if so, why the heck did it JUST NOW start coding - after replacing the vacuum leak...??

I think I may set this mutha on fire!!!

:banghead:

Thanks for hanging in there with me...

The MAP sensor is that rectangular shaped thing on the passenger fender with three wires and a vacuum line on it. If the vacuum line is broken, you will get this code, so make sure that vacuum line is attached.

As to the oil pressure switch location, I posted where it is in a previous message in this thread. Under, and to the right of the distributor (actually, it's more on the driver side where the distributor is on the passenger side).

http://www.silicon212.org/9c1/images/engine.jpg
This is the engine bay in my car, from the driver's side at the front. Yours will be a little different, due to it being the bathtub Caprice and mine being the boxy Caprice. Mine is also carbureted, yours is TBI. However, the details we are wanting to see will be the same between the cars.
http://www.silicon212.org/9c1/images/osdetail.jpg
This is looking from the same angle, the closeup detail of where the oil pressure switch is. While the details of my engine are going to be different from yours (carb vs. TBI), this should be the same.
http://www.silicon212.org/9c1/images/msdetail.jpg
This is the location of the MAP sensor, from the same location as the other two pictures.
http://www.silicon212.org/9c1/images/mscloseup.jpg
This is a closeup of the MAP sensor.

KK, think I know where the ops is then.. will check that tomorrow and see if I can check the MAP (which is coding now - I do know where it is)...

Thanks again!!! <3<3<3

The purpose of the fuel-pump interlock is to shut off the fuel pump in the event of an accident/rollover etc - by blocking power flow to the fuel pump when the engine is off (no oil pressure). If the switch is bad or other wiring faults as noted above, the engine could look "off" to the circuit, preventing the pump from working.

I beg to differ. Most members in this forum are very adept at diagnosis and repair, current respondants included, but this is just another example of how easy it is to fall into the trap of misunderstanding just because "everyone else" says that's the way it is. I am relatively sure that anyone here can understand why with a little investigation, and will no longer fall into the trap of the "I read it here so it must be true" syndrome. It's very easy to become a victim, as I have.

Very simply, NO domestic GM vehicle uses the auxilliary oil pressure switch as a "fuel safety shut-off" device. Fords have a kinetic switch designed to stop fuel pump power in the event of a frontal crash. Many imports have similar systems. GM just simply does not.

Open your Helms manual (or AllData page) to the appropriate section, study the schematic of the fuel pump power supply, and you'll see that the auxilliary oil pressure switch is a redundant path for pump power, wired in parallel to the pump relay contacts, and NOT in series. The switch is only there to provide pump power in the event the relay fails.

I'll bet anyone here one of their favorite beverages that you can remove the electrical connector on your stock, domestic GM EFI vehicle after the engine is started and it will still run. Send me your address, and I'll UPS a bottle so fast it should still be cold.

Need some examples?

1980's ECMs:

http://72.19.213.157/files/MAFpower.gif

1990s PCMs:

http://72.19.213.157/files/S-TruckFPump.jpg

On many 2000 and later PCMs, the auxilliary oil pressure switch is eliminated entirely.

I must admit I was one of those you referred to Blue Bowtie. I also pulled out my ECM schematic on my computer and my Chilton's Manual. It supported what you said, and according to the schematic, the pressure switch is in parallel with the ECM to power the pump. The pressure switch is only really an issue if the ECM cuts off power to pump, and Chilton's say it will only do that if the ECM does not receive a referrence pulse from the distributor.

OK.

The CODE 33 cleared - I forgot to reattach the vacuum line to the MAP.

Back to it still won't crank, unless primed with gas in the TB. :(

I can't for the life of me find the oil pressure switch - can't get anyone mechanically inlcined to come help..

The pix are great! But, mine doesn't look exactly like that, nor do I see anything else that does for the o.p. switch :(

I do see where the wire goes from the distributor to the coil.. and it has 2 relays or w.e. on top. But I do not see anything to the right hand side (driver's) of the distributor.

Does anyone else have a picture of a 92 caprice oil pressure switch location or a link to where one would be found... I have looked for hours on hours to no avail ... and the book I got from Autozone (Haynes) doesn't have it labeled either...

Thanks for hanging in there with me!!!!!!!!!!

Thanks for pictures!!!


I promise I'm trying...

Got a digital camera... brb with pix, maybe someone can point out the oil pressure switch to me :)

Good lord!

How do ya insert the pictures from your computer here?? :P

http://www.automotiveforums.com/vbulletin/C:\Documents and Settings\LL\My Documents\My Pictures\1992 Chevy Caprice 305

Can someone email me at tirion777@yahoo.com with a regular email I can send my pix to so you can post them for me and maybe someone can label the o.p.switch..?

Thanks!! :D

If you guys are saying it is NOT the oil press switch... what else could it be?

:banghead: :banghead: :banghead:

Silicon has a good photo of the location of the switch. This is a slightly closer view of a similar setup:

http://72.19.213.157/files/TPIOilSwitches.jpg

To post photos or other images, upload the image file to a web directory. Add html code to your post to link the location of the file like this:

http://72.19.213.157/files/ImageString.gif

Substitute the address of the server and name of the file, and it should display like everyone else's.

Disregard the auxilliary oil pressure switch for now. It is of no consequence. You need to verify that the fuel pump is running upon intitial ignition power-up (for two seconds) and again whenever the ECM is receiving distributor reference pulses (during cranking and running). If the relay is operating, the ECM output is fine. Remember that the ECM will operate the pump relay for a two-second prime cycle whenever teh ignition is first turned on. The ignition must be cycled off for at least 20 seconds before the ECM will run a prime cycle on power-up again. The ECM will operate teh pump relay whenever it is receiving distributor reference pulses, as while cranking or running.

With the pump relay operating, you still need to verify that the relay is providing power to the pump, that the pump is actually running during cranking (whether the engine starts or not), and that the pump is producing at least 11 PSIG pressure (bare minimum of 9).

If there is adequate fuel pressure, the inlet screens of the Maxi injectors in the TBI pod could be plugging.

Another possibility is that the ECM is not receiving distributor reference pulses during cranking, but that is a remote possibility, since it seems to at least operate once you manually administer fuel to get it started. A quick way to test this is to connect a 'noid light to the injectors and observe it while an assistant cranks the engine. No light - No injector pulse.

There is also a very remote possibility that the ignition switch is failing, and that power to the INJ fuse(s) is not present during cranking. This would be very easy to test with a voltmeter. Again, that would be a remote possibility.

Very simply, NO domestic GM vehicle uses the auxilliary oil pressure switch as a "fuel safety shut-off" device. Fords have a kinetic switch designed to stop fuel pump power in the event of a frontal crash. Many imports have similar systems. GM just simply does not

Sorry, I have virtually no experience with the newer EFI setups. On my old Chevy Vega, the oil pressure switch most definitely was a cutoff for the electric fuel pump and this was the basis of my statement. I admit I stepped in it, and for that I apologize.

You wouldn't even want to count the number of times I've "stepped in it" - There isn't enough bandwidth here to even begin to list them all. I just read that same thing all the time, and it's amazing how fast that theory spreads.

Cosworth Vega, by chance?

You wouldn't even want to count the number of times I've "stepped in it" - There isn't enough bandwidth here to even begin to list them all. I just read that same thing all the time, and it's amazing how fast that theory spreads.

Cosworth Vega, by chance?

Unfortunately, no, if it was I'd still have it! It was a standard Vega with the 2.3 (140) engine, but it DID have the hotter cam with 2-bbl Holley on it.

I miss that car.

I was told elsewhere on the forum that the oil pressure switch only continued fuel flow if the fuel pump relay went out.

Blue Bowtie, wasn't it you who explained this to me in another forum?

Perhaps. I vistit a few different forums, and moderate at a couple. That's how I see that this misconception of the pump power system is so common.

Any luck on the TBI, tirion?

I think I've suffered moderate brain damage trying to fix my car..

I cannot for the life of me think straight now...

I have a friend over that brought his voltmeter, but now I cannot remember or find what we were going to check with it...

Can you test the IAC valve, the TPS or the TB.. or any other parts I'm having possible problems with with a voltmeter?

If so, what do I check and what should they read...?

Argh!

Sorry, thanks for help.. I see why mechanics make so much per hour now!



:banghead:

UPDATE:

Just checked the TPS and IAC valve with voltmeters and they ARE getting proper reading.

However.. I took the IAC valve to autozone, b/c the book said the spring should be adjustable with your thumb and a rocking motion (it wasn't).. they said to plug it back in and ground it... and it should uncoil and come outwards with the power applied.

It did not.

It will not.

Would the IAC valve if bad cause my non-starting problems and dyng when idleing..??

THANKS!!! :)


Don't want to just go buy another one and it not be the problem yet again (it's $45).

UPDATE:

changed out the IAC vlave - not the culprit either :(


:shakehead

Tirion, I've just read this whole thread, and two things are jumping out at me..

1) check your distributor pickup coil. Pull the cap off, unplug the pickup coil connector from the distributor module. Connect a voltmeter to the pickup connector wires, set it to AC volts. Crank the engine and look at the voltmeter - you should have at least 2.5 volts.

2) Check the coolant temperature sensor. This will require a data reader of some sort . Just check to see if the indicated reading on the reader is reasonable.....does it say 75 degrees before starting, or 175?

These are the first two things I'd check for no start, or poor low speed opeartion.

You can also check the CTS with an ohmmeter:

http://72.19.213.157/files/CTSMAT.gif

Will do! - first thing tommorow :)

thanks!

Will post results..

(worn out from stressin' over it)

Excellent information.

The coolant sensor is in the front of the engine on the intake manifold, and has two wires black and yellow.

NEW RESULTS (8-8-6):

With volt(ohm)meter:

1. Checked the pickup coil - tested out fine.

2. Checked TPS - power continuity was OK(5v when turned power on), however, the check for the throttle closed to full (sweeping from ~.5vclosed up to ~5vfully open) gave NO readings on the meter whatsoever. This was putting the pos. terminal to the dark blue wire and the neg. terminal to the black wire.

Have I found my problem guys??

Should replacing it give me juice now?

Part's on the way (TPS) - *crosses fingers*

;lkjsdf;kljhsdflkjsdfl;kjasdlkjfdalkjdf

nope.

That wasn't it either.

Think I give up.

NEW RESULTS (8-8-6):

With volt(ohm)meter:

1. Checked the pickup coil - tested out fine.

2. Checked TPS - power continuity was OK(5v when turned power on), however, the check for the throttle closed to full (sweeping from ~.5vclosed up to ~5vfully open) gave NO readings on the meter whatsoever. This was putting the pos. terminal to the dark blue wire and the neg. terminal to the black wire.

Have I found my problem guys??

Should replacing it give me juice now?

The TPS isn't the cause.

If you're having CRANKING issues as well as fuel delivery issues, then mayhaps your ignition SWITCH is bad.

So how about the coolant temp sensor (CTS)?

Couldn't find the CTS. Having a car guy come out tomorrow and do a diagnostic for $30.

I wouldn't recommend anyone ever waste money on the books in Autozone BTW.

Couldn't find the CTS. Having a car guy come out tomorrow and do a diagnostic for $30.

I wouldn't recommend anyone ever waste money on the books in Autozone BTW.

I resemble that remark! I have a copy of the Haynes B-body Chevrolet 1969-1990 manual and it helps me with things such as carburetor specs, electrical diagrams and schematics etc.

The CTS should probably be on the thermostat housing at the front of the engine. As was stated earlier, it will have two wires on it - one black and one yellow. The thermostat housing might also have a thermal ported vacuum switch on it - this will have two or three vacuum lines on it.

A CTS failure will set a trouble code and light up the SES light. This should set the computer into "limp" mode, but it shouldn't cut off the fuel pump.

I'm still trending toward the ignition switch as a failure point as it would explain both an intermittent ability to crank as well as the pump shutting down after a while - power breaks down at the switch, no more pumped fuel!

Gah!

guy just came out and checked it over and then used a noid light and said the injectors aren't getting pulsed. To replaced the ECM (PCM) - computer.

Said to make sure to remove the old EEPROM and put it back into the new one and to avoid bending any prongs.

Man.. if this doesn't make her fire up and go...

:disappoin

Hello all
I have a 93 4.3 s/10 Blazer and have the same trouble. I would have bet money it was the pump.I replaced the pump (nope not it) if I shoot gas in the thottle body it will start till the gas is gone then just crank.Changed the relay on the firewall (Nope not it either) ??? But have power at the relay. The plug at the pump/sender is good but no power out of relay ?? I was looking for a fuse under the dash thinking maybe it cut off the power.. so wind up for now is I ran a hot line from the fuse box to the pump so I could use the truck till I find out whats wrong. There is a test plug on the fire wall if checked with a light it comes on for the 3 second start up...I am wondering about the ignition how would I check it out???
Anyway like to know how tirion makes out with the (PCM) I might be next soon.........
THANKS AHEAD OF TIME VINNY FOCH

Gah!

guy just came out and checked it over and then used a noid light and said the injectors aren't getting pulsed. To replaced the ECM (PCM) - computer.

Said to make sure to remove the old EEPROM and put it back into the new one and to avoid bending any prongs.

Man.. if this doesn't make her fire up and go...

:disappoin


Before you put a new computer in, do this.....

Remove the four wire connector from the distributor. Turn the ignition to 'Run'. Now take a test light connected to the positve terminal of the battery, and touch the terminal from the purple wire with the white stripe. Every time you touch this wire with the test light, the injectors should fire.

If they do, the ECM can drive the injectors. If they don't, it can't and is probably suspect.

I don't have a test light... is there another way to perform this test? I have a voltmeter..

Found a used one for $40 with a 6 month warranty. When I went to pick it up, they didn't have it in yet.. be tomorrow morning. Called around looking for another (ECM) - and the other places were asking me which of the 2 I needed.. said there were 2 that had letters AB... and something else in their part number. But I have it pulled right here and there are no such letters.

It reads:

Service Number 16136965 AYAL

and *86AYALKB21781024*

shrug

always something...

The eight-digit part number is important (16136965). The four characters after the number are meaningless as long as you have your original MEMCAL/PROM. The four letters are the broadcast code for the PROM, and denote exactly what engine, trans, year, etc. the programming is for.

Good luck with it. I suspect you may still have some issues after the ECM swap, but you might be lucky.

Can't do anything till tomorrow afternoon...what else could it be??

:crying:

Can't do anything till tomorrow afternoon...what else could it be??

:crying:

Well, let me see here. I do believe that I posted, twice, to check your ignition. I'm going to ask for a clarification here - by "not cranking", do you mean not turning over (starter not rotating the crankshaft, as with no battery) or do you mean "not starting"? They're two different things.

Let's do a process of elimination. You say that your car starts and runs for a while if you prime it. If the injectors were not being pulsed by the ECM, the engine would run long enough to clean out the liquid gasoline from the intake (and it would run roughly at that), about 5 seconds tops before it shuts off due to lack of fuel. You say it runs for 30 minutes or so - therefore the injectors MUST be getting pulsed. PROBABLY NOT the ECM.

The problem you are experiencing is generally due to weak fuel pressure or an intermittent electrical flow through the fuel pump. This being the case, have you checked:

Fuel Pump Relay
Oil Pressure Switch
Voltage at Fuel Pump

??

If the fuel pump relay is toast, you will be running current through the oil pressure switch. If this is bad, you will have problems!

Using a volt-ohm meter, ohm out the following-

Fuel Pump Relay - across the contacts - when the coil is energized, you should have 0 ohms across the contacts. You must perform this test with the wires removed - use battery power as a source for the coil.
Across the two opposing tabs on the oil pressure switch (|_|), with the wires pulled and the engine running - should be 0 ohms.
Across the coil of the relay (again, wires pulled off) should be no greater than 5 ohms (ideally 0, but allowing for some to count for resistance due to the inductance of the coil).

Using the same volt-ohm meter, test for voltage on the following with the engine running-

Across the coils of the fuel pump relay, wires connected, should be ~12 volts (13.8 etc).
At the fuel pump, positive lead on the 'hot' wire to the pump and negative on any exposed metal attached in some way to the frame, should be ~12 volts.

If you have infinite resistance (or anything greater than 1 or 2 ohms) across either the contacts on the relay, or the oil pressure switch, or anything greater than 5 ohms across the coil of the relay, these items are failed. Replace as necessary.

If you have no voltage at the pump or the coil of the relay, with the engine running, check for a bad fuse in either the pump or relay circuits. If there is no power to the relay, check the fuse and also the output at the ECM. If the fuses are good, check for wiring faults. Check for the presence of voltage at the ignition switch with the key on. Look at your wiring diagrams for the correct terminals to test. If voltage at the relay coil is good, but fluctuates at the pump, replace the relay.

You have a voltage problem. If a sensor had failed, the ECM will default to table data to run the engine, set the appropriate trouble code, and light the SES light. It should continue to run, however.

Right. Does turn over, does not 'start.' Sorry, wish I knew more of the lingo - by no means mechanically inclined at all. :D

By 30 minutes or so - I mean ONLY if I hold my foot on the accelerator. As soon as I let it return to IDLE - it dies.

I looked at the noid light and it did not come on at all when connected to the injectors. The mechanic guy said it was the ECM. Shrug. That's all I know so far. I get one tomorrow for $40 bucks, and will try my best to follow those excellent instructions with my voltmeter :)

Thanks for hanging in there with a noobie!!! :)))

Right. Does turn over, does not 'start.' Sorry, wish I knew more of the lingo - by no means mechanically inclined at all. :D

By 30 minutes or so - I mean ONLY if I hold my foot on the accelerator. As soon as I let it return to IDLE - it dies.

I looked at the noid light and it did not come on at all when connected to the injectors. The mechanic guy said it was the ECM. Shrug. That's all I know so far. I get one tomorrow for $40 bucks, and will try my best to follow those excellent instructions with my voltmeter :)

Thanks for hanging in there with a noobie!!! :)))

It does sound like you have a pressure problem. Have you put a pressure gauge on it? As Blue Bowtie suggested, it should be +/- 2lbs of 11 PSI. In fact,

With the pump relay operating, you still need to verify that the relay is providing power to the pump, that the pump is actually running during cranking (whether the engine starts or not), and that the pump is producing at least 11 PSIG pressure (bare minimum of 9).

If there is adequate fuel pressure, the inlet screens of the Maxi injectors in the TBI pod could be plugging.

Didn't have a pressure gauge.. but it dispensed what looked to be the same amount of gas/pressure from the filter break and at the TBI with both the old and new (I replaced it with a new one) pump.

I do remember the "check engine light" coming on several times, intermittantly over the past couple months, before it died on me.. when I would turn the car off to check the codes.. none would show. And now, the noid test showing no pulsing.. does that sound a little like it could be the ECM.. even though, it is giving and clearing codes now.. shrug. Up late, no new news, just thought I'd reply. Will post results of ECM replacement tomorrow afternoon (today actually)..

Didn't have a pressure gauge.. but it dispensed what looked to be the same amount of gas/pressure from the filter break and at the TBI with both the old and new (I replaced it with a new one) pump.

I do remember the "check engine light" coming on several times, intermittantly over the past couple months, before it died on me.. when I would turn the car off to check the codes.. none would show. And now, the noid test showing no pulsing.. does that sound a little like it could be the ECM.. even though, it is giving and clearing codes now.. shrug. Up late, no new news, just thought I'd reply. Will post results of ECM replacement tomorrow afternoon (today actually)..

If you're going to do this, and do it right, you're going to need the proper tools. You NEED that gauge. I've said it before and I'll say it again - you cannot gauge pressure by looking at a stream from a Schrader valve. All that will tell you is that the pump is working to some degree - it won't tell you that the pump is working properly.

Not only do you need a guage, but it sounds like you need a scan tool capable of pulling manufacturer specific codes. Most only pull the P0*** codes, not the P1*** codes..

Nothing this old with TBI has ODBII. All he needs is a paper clip to get the codes.

OK - replaced the ECM - same problem.

:banghead:

Well, since I've replaced the entire fuel system (almost) - what's left?

The fuel pump relay - well according to the book, where the say it is, there are 2 relays (square type). Which is which and what is the other one?

This completely sucks. obviously over my head

Would a scanner _definately_ tell me where my problem is located?

I've expended my funds for the month on this already - just don't want to dig deeper..

maybe I already have...

BTW:

Now I'm getting a code 22. TPS.

I just replaced that!

Before you put a new computer in, do this.....

Remove the four wire connector from the distributor. Turn the ignition to 'Run'. Now take a test light connected to the positve terminal of the battery, and touch the terminal from the purple wire with the white stripe. Every time you touch this wire with the test light, the injectors should fire.

If they do, the ECM can drive the injectors. If they don't, it can't and is probably suspect.

Have you done this yet???

I think Supergumby is onto something here according to the 89 FSM I have studying tonight.

One other thing I would add is that the FSM states that "a grounded CKT423(EST) may cause a "no-start" or a "start then stall" condition"

Now my question to all of you is this... If the ignition module/EST/the little black electrical piece located under the distributor with one two wire plug and one four wire plug going to it fails.... won't this cause the no start? But will it also allow it to still start if he dumps the fuel in as described in one of the first posts?

Have you done this yet???

I think Supergumby is onto something here according to the 89 FSM I have studying tonight.

One other thing I would add is that the FSM states that "a grounded CKT423(EST) may cause a "no-start" or a "start then stall" condition"

Now my question to all of you is this... If the ignition module/EST/the little black electrical piece located under the distributor with one two wire plug and one four wire plug going to it fails.... won't this cause the no start? But will it also allow it to still start if he dumps the fuel in as described in one of the first posts?

EST = Electronic Spark Timing. The module in the distributor, with two wires on one side and four on the other is the ignition control module. The ECM controls EST. A failure of this module generally results in a no-start condition which all of the fuel in the world won't cure. Sometimes the module can fail in a manner that lets the car run - somewhat - usually only on a couple or a few cylinders so it will run like crap. I suppose there could be a heat-related issue with this module that cuts it out, but it doesn't have anything to do with fuel delivery.

Don't have a test light. Is this what I need?

http://cgi.ebay.com/ebaymotors/Cornwell-Tools-Fuel-Injection-Test-Light-GM-SCPI_W0QQcmdZViewItemQQcategoryZ35625QQihZ016QQite mZ260019237855QQrdZ1QQsspagenameZWDVW

Will try and get another ride to find one tomorrow at a parts shop.

Do you mean one of those 'noid' lights?

If so.. run a wire from one prong of the noid light to the pos. terminal of the battery.. then touch the other prong to the purple with white stripe plug location.. this will fire the injectors if good?

thx!

Nothing this old with TBI has ODBII. All he needs is a paper clip to get the codes.

Ahh, i just noticed it was a '92, but he could get a scanner that would show the datastream and look for anything odd while it's running..

That's a noid tirion. And I don't think it's the correct one for TBI. I think from reading the FSM, you can use just a standard $5 test light, one with a clip on one end and a ice pick style tip with a bulb on it on the other.

Well.. the guy that charged me $30 to diagnose and tell me to get a new ECM is coming back out - no charge, to check the ignition switch for me.. printing this out (at his request) for him to read.

Will post results as soon as I have them.

Thanks again for all your HELP!!!

Sorry, I'm such a novice.. but I am learning little by little.. great site!

Latest results:

...with the new ECM - the injectors with a noid light plugged in each light once when turning engine over, but do not continue to flash.. (this did NOT flash prior to new ECM).

As to this:

"
Remove the four wire connector from the distributor. Turn the ignition to 'Run'. Now take a test light connected to the positve terminal of the battery, and touch the terminal from the purple wire with the white stripe. Every time you touch this wire with the test light, the injectors should fire. "

---this test did cause the injectors to fire. The guy that tested it said this was bypassing the ignition module.. told me it was under the distributor cap.. to remove the rotor, the 2 switches on the outside, one switch on the inside, 2 bolts and that should be it.


Waiting for a ride now to go get one of those ($35).

Sure hope this gets her going... can't imagine it being anything else..

:ylsuper:


Lemme know what ya think.. if this sounds right or not.. THANKS!@!

Thanks!
Thanks!
Thanks!

Well.. she lives! :grinyes:

The ignition module got her to crank on her own now.

But - now I'm still getting a CODE 22 (TPS circuit). Just replaced it brand new part.. removed and put back in to make sure it was lined up right - both the old and the new give the same code 22.

Checked for vacuum leaks cannot find any.

Runs now with service engine light on and very badly, like it's in 'limp home mode' or whatever - like the timing is missing.. very rough. But isn't dying.

Any other idea?

Thanks!!

Well now you need to check that circuit, TPS, to see what readings you are getting there. It's quite possible the new part is bad. But I'd guess there is a frayed wire somewhere.

22 is a TPS low code.

When you replaced the sensor, you probably got it set a little too low. It's slotted, just loosen the screws and rotate it to adjust it.

Needs to be about .50 volts at closed throttle.

So.. let me try to understand this right.. I need to take off the sensor itself (held on by the plug and 2 bolts).. and then.. what's left inside is a slot- looking tab that turns clockwise.. is that the part that needs adjusting? If so, how exactly (sorry - remember I'm not a mechanic or even close :P) do I do that? When I slip the TPS sensor on and off of this slotted piece, it only can go on one way and before aligning the 2 bolts I have to rotate it clockwise a few degrees. Is there a way to adjust the slot piece itself before adding the sensor onto it? And if so, how do I know how far.. just do it until the code goes away?

Thanks for your patience guys. It's frustrating, but I'm still hangin' in best I can ..

The TPS signal wire could be broke.. Looks like the blue wire leaving the TPS on my diagram..

I believe your TPS is non-adjustable..

The holes that the screws go through the TPS itself are oblong (slotted), so that the whole sensor can rotate a few degrees in either direction, and set the idle voltage.

Loosen the two scres slightly, and rotate the sensor a little to get about .5 on the signal wire at idle.

OK.

Loosened screws and tested with voltmeter in each position it could wiggle and did get the .45ish +/.075 with throttle closed fully. And scrolled smoothly up to 4.25 +/- .25 fully open. Did this with both the old TPS and the NEW TPS with the exact same results. Disconnected the battery and cleared the code 22. Upon cranking, the code comes back.

The car seems to be running fine at idle and while giving throttle. But when I put the car into gear is where it stumbles and runs badly.

Driving, the power brakes seem to have no power until the rpms are higher. I have checked all the vaccuum lines I can find, both spraying barb cleaner at all junctions (with no idle increase or decrease) and by removing and checking manually for a good suction (which they had).

So... if it SAYS code 22.. and it ISN'T the TPS... what in the heck is going on???

:banghead: :banghead: :banghead: :banghead: :banghead:

Thanks in advance!!

And I did inspect the wire plug and harness and wires back to the firewall inside the harness.. and they looked very good with no frays, etc..

After doing more research online.. it seems it has to be a vacuum leak.. someone said the spark plug gaps too.. but I haven't changed those recently (tuneup about 6 months back).. but I did remove the distributor cap and rotor button to change out the ignition module (THANKS FOR THAT TEST!!! :) ).. could anything in there have been bumped loose to give this code?

And.. the vacuum issue: there is a small metal oblong (flying saucer looking thing on the left hand side of the engine, looking from top down from the front of car, that a vacuum hose connects to. is this the source of the vacuum pressure (plunger)? if so, could this part be going out or off..?

Thanks!!

More reading shows maybe the plug itself needs taking apart/replacing... shrug. ??

Oh yeah.. on this model 92 305 5.0L TBI, the TPS is supposed to be non adjustable (TPS cannot be adjusted, the TPS has an auto zeroing feature.).

You can remove the TPS connector and inspect the pins and sleeves. If there is a connector problem, replacements are available.

Oh yeah.. on this model 92 305 5.0L TBI, the TPS is supposed to be non adjustable (TPS cannot be adjusted, the TPS has an auto zeroing feature.).


My mistake - that's right.

Like Bowtie suggested, look at the connector terminals. make sure they're not 'bored out' from using test leads on them. If the terminals look OK, lightly tug on the wires on the TPS connector, make sure the wires haven't broken inside the insulation. The wire will stretch when you pull on it iff it's broken inside.

If that's all OK, connect the voltmeter back up to the connector with it plugged into the TPS. Turn the ignition on, and watch the meter while you slowly move the throttle to ful open and closed. Make sure the voltage doesn't drop out anywhere (go below idle voltage). If it does, that TPS is bad.

But look closely at the connector first.

Sorry for the bad info.

Will do.. been away from car last day or so..

WoooHoooOOOOOO!!! :smokin:

It was the TPS plug afterall!

I have been looking for a replacement, but none of the salvage yards have had one compatible in yet.. and didn't want to order parts from Chevy - figured I'd have to buy the whole wiring harness..

So.. I just went outside at 1am and rolled up tiny pieces of aluminum foil and packed each of the 3 terminals about halfway full (not too tight).

Smooth as ever! No CODE 22!! No idle up and down.

So... I'll eventually get around to replacing the plug. But for now, my cracker engineering seems to do the trick!

THANK YOU ALL SO MUCH FOR YOUR HELP AND SUGGESTIONS!!!

I could NOT have done it without this forum and the people that responded and helped me.

THANK YOU THANK YOU THANK YOU!!!
THANK YOU THANK YOU THANK YOU!!!
THANK YOU THANK YOU THANK YOU!!!
THANK YOU THANK YOU THANK YOU!!!
THANK YOU THANK YOU THANK YOU!!!
THANK YOU THANK YOU THANK YOU!!!
THANK YOU THANK YOU THANK YOU!!!
THANK YOU THANK YOU THANK YOU!!!


:biggrin: :biggrin: :biggrin:

Glad to see that you got it figured out.

Very simply, NO domestic GM vehicle uses the auxilliary oil pressure switch as a "fuel safety shut-off" device. Fords have a kinetic switch designed to stop fuel pump power in the event of a frontal crash. Many imports have similar systems. GM just simply does not.
do new fords not have and inertia fuel shutoff, to kill pump power in a rollover, or are we talking about the same things?

do new fords not have and inertia fuel shutoff, to kill pump power in a rollover, or are we talking about the same things?
I believe they still do. They've been using them for a pretty good while now. My '88 Ranger GT had one. Pretty easy to kill the fuel pump power for various reasons... Just smack it with a rubber hammer. I wonder why GM hasn't installed any fuel cut-off devices?

EDIT: I've seen a few Ford's with intermitent drivability problems that turned out the switch had been tripped, but they still ran. If you want to get away from the law, just go down a washboard gravel road, they'll kill the pump every time.. :)

A possible answer to your question is another question - When was the last time you heard of a GM vehicle having fuel system problem in a crash? Other than some over-zealous reporters at NBC Prime Time using dynamite to blow up a 1984 C/K pickup fuel tank for the visual effect on file film, they really don;t seem to have problems with that. On the other hand, deserved or not, Fords have had a notorious reputation for fuel problems in accidents since the infamous "exploding Pinto" and Mustang II days and more recently from all the Crown Vic police cars incinerating themselves in accidents to the point of several state police departments threatening legal action against Ford. I can understand why they would at least do something to make it look like they were trying to build an accident-safe fuel system.

In most rollovers, the engine stops. If it doesn't stop from impact or wire harness damage, it won't run very long with the oil pump sucking air. On a GM/Delphi ECM/PCM, as soon as the engine stoips the fuel pump relay is dropped two seconds later. If the auxilliary oil pressure switch does not have at least 4 PSI to provide backup power to the fuel pump (and it probably won't if the oil pump pickup is upside-down) the pump will stop within two seconds of the engine. In a frontal impact severe enough to damage the fuel line set (which are generally routed in a very protected location on most GM vehicles) there would likely be other damage to the engine itself and/or the engine controrl system which would kill the engine. After stalling, the pump will shut off similarly. Ford needed to kill the pump because some of them apparently ran constantly whether the engine was turning or not so long as the ignition was on. A more sophisticated engine control system solves that.

Ahh, good reading.. You know, my monte took a 45 mph hit to the rear while I was at a stoplight(with me and a fam. member in it), and it was purring like a kitten the entire time. I got hit so hard, it clicked on the highbeams, broke both headrests and slammed it in low gear(I was in D). You know, every since then I've had that surging problem.....

Ahhh... NOW we get all the details. I had the same sort of thing happen in a Fiero. It woudl start and run fine but intermittently go lean on me and have "fits". I finally added "2+2" and arrived at "4" (after a complete tune, TBI checkout, etc.) and decided to take a look at the fuel pump:

http://72.19.213.157/files/FieroPump.jpg

It had been jarre3d enough by the impact to pull it loose from the tank pedestal, but not completely. On occasion is would leak enough fuel pressure to go lean, stall, etc. That downpipe from the top of the tank unit to the pump is supposed to be straight (90°) and was also bent from the impact/inertia.

Hmm, that looks rough.. I think I'll be dropping the tank this week..

BTW, was that sock filter WHITE once?

Hmm, that looks rough.. I think I'll be dropping the tank this week..

BTW, was that sock filter WHITE once?

The ones I've seen are black, although there might be other colors as well.