fuel pressure regulator ?

on a 94 jimmy 4.3 vortec Vin"W" if the regulator was faulty- is it possible for a regulator to let it start everytime, but give it a lopey idle and s urge while at low speeds and no power at high speeds? I mean like allowing to much fuel to return to the tank? I have replaced the nut kit due to leaking lines, and I just read a post from Old Master about fuel pressure and the regulator. It has no trouble starting, I thought I had amiss at idle but I dont think its a miss anymore, I think its a fuel problem like MT had said before but I never had any way to check the pressure and I finally can check my pressure which Im doing in the morning since we got the snow storm. I thought that if the regulator went bad it would dump gas into the intake and get into the oil, or is that if the diaphram ruptured? What should my pressure be when the key is on and engine not running? I have already replaced the filter too.

try doing a search in this forum "fuel pressure" and you should be able to find the correct specs for your year. Old Master also has a nice pic of a home made shut off tool to find out where any fuel pressure drops are with a detailed part description and numbers. I used it and it works great...I just cant remember how to copy it from my messages in here to show you.

I think you should be around 58-64 psi with key on, and stay above 53 psi for atleast 5 min after you turn key to off. "NOT POSITIVE THOUGH">>>>

on a 94 jimmy 4.3 vortec Vin"W" if the regulator was faulty- is it possible for a regulator to let it start everytime, but give it a lopey idle and s urge while at low speeds and no power at high speeds? I mean like allowing to much fuel to return to the tank? I have replaced the nut kit due to leaking lines, and I just read a post from Old Master about fuel pressure and the regulator. It has no trouble starting, I thought I had amiss at idle but I dont think its a miss anymore, I think its a fuel problem like MT had said before but I never had any way to check the pressure and I finally can check my pressure which Im doing in the morning since we got the snow storm. I thought that if the regulator went bad it would dump gas into the intake and get into the oil, or is that if the diaphram ruptured? What should my pressure be when the key is on and engine not running? I have already replaced the filter too.

Fuel pressure regulators can leak pressure several ways.
External or bypass back to tank.

When the upper platinum if off always prime up pressure and look for external leak.

And watch for fast leak down.
But beware tkat a check valve in tank can cause a fast leak down to.
Pressure specs are 55/61 lbs on yours.
First thing.
Run the full pressure test and post back readings.

If your pressure is low or leaking off.

If You fuel pressure is to low or leaking down .
Specs on it is 55/61 lbs of pressure
Here is some guide lines of fuel pressure checking.

Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 55-66 fuel pressure.
Cold start should be 60 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 55/61 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
If pressure does not come up with return line pinched or blocked off.
Go to fuel filter and hook a gauge direct to a line at fuel filter.
Pressure should come up to 75 or more and will hold after fuel pump is turned off.
If it leaks down there after fuel pump is turned off it is LEAKING BACK THREW PUMP CHECK VALVE OR PUMP MODULE LINES.
Post back your fuel pressure readings.
MT

ok, do I leave the key on after the pump turns off? When I had the plenium off I did prime up the system and did not see any leaks. I just replaced the filter so I know the lines will come off easilyto test full pressure.

Flip the key on a couple of times to get full pressure or just jumper fuel pump to build up full pressure and turn pump off and watch for fast leak down.

dose the tail pipe shoot black smoke on start up?

does you oil have a stronge gas smell?

if so you may be close on the fuel issue. CFI spinder maybe a better thing to check. When the spider injection system gose bad what happens is the fuel lines in the mainifold crack allowing fuel to exscape into the oil witch will make the engine act like its missing. while driving it will not have the power it needs.

no I dont have any black smoke, I have replaced the return lines in the plenium already and primed it up when I had it apart and didnt see any leaks inside

Then if it dosent leak i would look to other possibles like ign. from what you said about surging and lack of power at high speeds almost makes me think it would be a coil issue. Does the car stay running at idle or dose it struggle?

it stays running, doesnt struggle to stay running, starts every time, has never died on me or anything

it used to be after ir ran for about 2 minutes then it would start, now its as soon as it starts it does it,

have you replaced the fuel filter? dose it have a long start up time meaning how many sec dose it take to start the first time?

I cleaned the cap and rotor, the rotor looked new, the cap had like a white corrosion on the tabs, I put new wires on it and new ac delco plugs about 2 weeks ago

yes I have replaced the fuel filter in the last 2 weeks also- start up time is about 2-4 seconds and this is every time, every once in a while it will act like a dead battery then fire right up, but my volts are good- not very often though

Heres a long shot. I did some digging in my mechanic notes on your car. I would like you to try something. The wires from your injector go throught the intake. they should be a blue and red wire located infront on the right of the Throttlebody. have the car running and move the wires around. If I am right the car should either run better or show you a worse condition. If thats the fact then you need to replace you fuel injector harness. I ran into this 4 years ago when i was working in a shop.

I cleaned the cap and rotor, the rotor looked new, the cap had like a white corrosion on the tabs ....

The "corrosion" is supposed to be there. When the distributor cap is replaced, silicone dielectric grease is applied to each terminal, inside and out. When the engine is running, the current passing from the rotor to the cap terminals crystalize the grease.

ok, I will give it a try and let you know if anything happens

so if my pressure holds without the return line being closed off that means my regulator is good and the pump is good as long as its with in specs? DO I leave my key in the on position or put it in the off position?

so if my pressure holds without the return line being closed off that means my regulator is good and the pump is good as long as its with in specs? DO I leave my key in the on position or put it in the off position?

You need to go threw the complete pressure test.
And post back all pressure readings.

well I went and rented the tester and this is what I got so far
key on and engine off 56-58lbs
after 6 minutes it was down to 50
running was 54lbs and I reved it up and it dropped to 50 then went up to 56
I rented a complete fuel system kit but there is no way for my to hook it around the filter to test direct pressure also I dont know which line is the return line, and the only place I can see where they are rubber is above the tank

also the book that came with it says the pressure should be 56-66

Specs are 55/61 lbs.

You can block return line to check direct fuel pump pressure.

You should run it a 1/2 hr or more with the gauge hooked up.

On the road you should see 56-57 light load and coasting and 59-60 on a pull heavy load.

The pressure you have is a hair low running pressure but should not be giving you much problem.
As long as you have good cold start pressure and the fuel pump test good on direct pressure after engine hot after 1/2 hr running.

I would check engine vacumn at idle and at 2K rpm to check for exhaust back pressure and slow time.

Give us your vacuum readings.

Have you set/checked base timing with bypass wire unplugged?>

what about the fast leak down? how do I get the vacum readings? I dont have no cats or muffler on my vehicle- just goes into a cherry bomb and another straight pipe

guess my leakdown is in specs- sorry bout that, no I havent got the timing checked yet, I did notice that I havent driven it since friday, and I went out to start it and pull it in the driveway today and while it was idling it didnt have the miss until it ran a few minutes

also what do you mean by slow time? here are a few other things I should mention, when I start it the first time for the day and put foot on brake to put in gear, as soon as I pull it out of park it revs up then down, also if I have the cruise set on the highway and I tap the brake to stop the cruise it will do a short rev also- I know that its not normal. But today it was idling fine after starting and then when I put it in gear it was really rough, but if I give it a little gas it smoothes out, could it be my coil or ignition module? The coil looks rather old and kinda like a rusty color and I also noticed that when I had my distributor cap off- the 2 screws that hold the module down- the tops of the screw were burnt a white color- would that indicate moisture mabye under the module or something? looks kinda like the carbon tracks a cap would have on the inside on the metal tabs where the rotor fires- I have never seen any have the white substance on them

Try using an AC Delco cap and rotor..

I'm having the same issue! So far I've replaced ECU, TPS, MAP sensor, Fuel Pump, new wires and plugs, new cap, new rotor button, new coil, and ignition control module... Don't know what the issue is! It starts right up! Like nothing is wrong. But when I get in to drive, it backfires both in intake, and exhaust. That only happens when I floor it. It hesitates quite a bit, then finally gets going really nicely. But it's like I have to ease off on the gas pedal to get it to act half assed right, but still jerks and hesitates! It's not out of time. Don't know what the hell is going on! No engine codes are being thrown!

only thing mine is doing is it has a miss while in park or at at light and surges at low speeds and while your on the highway you have no power, going up hills it drops to about 55 or 60 its like there is nothing there

in deep- have you looked on the inside of your plenium for washing, mine had a bad hesitation when I got it and my return lines were leaking, and it kinda sounds like yours, mine didnt have any trouble starting and hesitated up to about the point of shifting in to 2nd then it would smooth out, you might want to check that, I took the big round thing off the top of my plenium and used a flash light and seen the drivers side was really clean and thats where the return lines are

in deep- have you looked on the inside of your plenium for washing, mine had a bad hesitation when I got it and my return lines were leaking, and it kinda sounds like yours, mine didnt have any trouble starting and hesitated up to about the point of shifting in to 2nd then it would smooth out, you might want to check that, I took the big round thing off the top of my plenium and used a flash light and seen the drivers side was really clean and thats where the return lines are
The big round thing you're talking about is probably the fuel injection, and I have tried, but that thing is in there pretty good. I wonder if I actually have to remove the plenum to take the F.I. off?

no its not the feul injection, I think its called an IMTV valve, its under the vortec cover and has 2 torq screws holding it down

if you take the screws out and kida spin it a little and maybe use a screwdriver to pry up easily it should come out and I bet you will see your problem in there, I know there is an O ring on it and it is actually has a little bit of weight to it as well

you could take the top off and as long as you dont damage the gasket you can reuse it, but if its clean on the drivers side then its the return lines and if its on the passenger side its the regulator

no its not the feul injection, I think its called an IMTV valve, its under the vortec cover and has 2 torq screws holding it down

Is it near the back of the manifold? I thought that was the F.I.? What's IMTV stand for?

yes its near the back under the vortec cover It stands for Intake manifold something valve- I forget now- but it has a wing type deal on it and I guess that it turns as more air is entering the intake, it will come out, it is hard to see in there though so it may be just as well to take the top off so you can have a good look, the injection spider is located inside, just dont mess with the lines- could cause more problems

yes its near the back under the vortec cover It stands for Intake manifold something valve- I forget now- but it has a wing type deal on it and I guess that it turns as more air is entering the intake, it will come out, it is hard to see in there though so it may be just as well to take the top off so you can have a good look, the injection spider is located inside, just dont mess with the lines- could cause more problems
Will do... Thanks for the info.

no problem, my lines werent leaking alot but it fills the intake up with gas - I mean mine was barely leaking, the return are 60.00 and the regulator is 50.00 just have to see which one you need, just look for a really clean side inside

no problem, my lines werent leaking alot but it fills the intake up with gas - I mean mine was barely leaking, the return are 60.00 and the regulator is 50.00 just have to see which one you need, just look for a really clean side inside
I unplugged the sensor, and took the 2 screws out, but man, that shit is seated in there pretty good! Having a helluva time turning it, or even getting it out! Looks like I may have to pull the plenum. Don't they make computers that connect OBD-1 and will read which sensors are failing, etc...?

I think, but if those lines are leaking its not gonna show up on a reader, it only takes about 10 minutes to take the top off- the regulator isnt gonna show up either

is your engine light on? if so you can use a paper clip to get the codes out of it, mine showed oxygen sensor but that was because my lines were leaking

is your engine light on? if so you can use a paper clip to get the codes out of it, mine showed oxygen sensor but that was because my lines were leaking
No codes. At first, I had codes 22,23,43,44... I replaced everything mentioned earlier in the thread. TPS, MAP, ECU, Ignition Coil, Ignition Control Module, cap, button, wires, plugs, fuel pump.... lol I have replaced everything damn near. Hooked a code reader to it, rather than jumping pins, and got 23, which is TPS. (I had just replaced TPS that day) After clearing the codes, I don't get any more codes at all. Runs like a freakin scalded dog when it gets out of the hesitation and finally catches. So I know the timing and fire is fine... It's gotta be a fuel thing. I get both intake and exhaust backfires when this issue occurs, when I floor it. So I poured a large bottle of rubbing alcohol in the tank to see if I had water in the tank, but no results as of yet.
Like I said, tried removing the damn IMTV and that sucker won't budge. I even used a chisel wedged beneath it and tried prying it up... No go. Have a buddy coming over with another computer to see if we can see if relays are opening/closing properly, if the computer will do that. Hopefully, we find the issue, if not, I will then proceed to remove the plenum for further inspection.

Im telling you I believe the problem is inside the plenium, mine did the same thing- what happens is all the extra gas in the intake and its overloading, here is something you can do pull out the #3 plug plug and # 4 plug and look at them I bet at least one of them dont look like the others on mine it was the #3 plug your getting the leaking fuel and no computer will show this

Im telling you I believe the problem is inside the plenium, mine did the same thing- what happens is all the extra gas in the intake and its overloading, here is something you can do pull out the #3 plug plug and # 4 plug and look at them I bet at least one of them dont look like the others on mine it was the #3 plug your getting the leaking fuel and no computer will show this
I don't doubt you, friend... That's why I'm lining it up to get these parts up. I just hope it solves my problem. As of today, I've dumped $900 into my truck in the last two weeks...

I will almost promise this is your problem as I just fixed mine about 3 weeks ago, let me know what you find

I will almost promise this is your problem as I just fixed mine about 3 weeks ago, let me know what you find
Roger that.

figure out anything?

figure out anything?
I finally got that IMTV off. Didn't see anything. So I took the plenum off for shits and giggles. No clean spots or fuel puddles. So I went to the salvage yard, found a running engine, and got the fuel setup out of it, just to see if my injectors were bad. Only paid $58 so no biggie, but anyhow, now it won't start at all... lol So today, I'm switching back, then back to the drawing board. What had happened last month was a wire beneath the steering column had been pinched, and caused two wires in the harness to burn. Those were fixed last week, for $700, and what I'm starting to think is that when I replaced that fuel pump a few weeks ago, the existing short may have damaged the F.P. b/c it ran great for a week after I replaced the damn F.P. then started acting like shit again on me. That's when I discovered the wire damage and had it fixed.

are you getting fuel and spark?

are you getting fuel and spark?Got great spark. Replaced everything except the distributor base itself. Checked that already. Fuel pressure was only 12-15 psi when I checked it before the guy got it fixed when he repaired the wiring. That lasted for all of 100 miles before it started running like dirt again. So I'm thinking the short he repaired did damage to the F.P. I don't know. Replacing the fuel pump will be the last thing I do before I just give up. This is my only vehicle, and time is of essence... Ya know?

fing your f.p fuse and see if you have 12 volts to both sides- should have 12 on one side and turn the key on and have 12 to both sides

fing your f.p fuse and see if you have 12 volts to both sides- should have 12 on one side and turn the key on and have 12 to both sides
You mean the relay? Or is it a fuseable link?

relay I believe that is how it works or go to where the fuel pump plugs in and see if you have 12 volts there

relay I believe that is how it works or go to where the fuel pump plugs in and see if you have 12 volts there
Will do. AFTER I go back to my original injector and spider setup... :(

Here's the last thing I'm going to try. I'm going to bypass the factory wiring from relay to pump, and replace it with 12 ga. Same with the ground. I'm also replacing the fuel pump as well. Will have some news tomorrow.

NOTHING! NOT A DAMN THING. New freakin everything and the sorry POS is STILL not running. I GIVE UP

did you see if you had 12 volts at the pump? change the relay with another one and see if that works

did you see if you had 12 volts at the pump? change the relay with another one and see if that works
I fixed it... I put a new injection system in it, including the F.P.R. I think it was needing the F.P.R. however. I replaced it all anyhow, because all the sensors got replaced, and have new plug wires, and fuel pump. The gas mileage oughtta be phenomenal now though! I can actually use preventive measures to prevent ANY build-up in them now. The damn truck runs twice as nice now. I thought it ran like a scalded dog before... lol

did you use the one you got for 58.00 or did you get a brand spankin newbie? lol How much was it?

did you use the one you got for 58.00 or did you get a brand spankin newbie? lol How much was it?
I got Brand New setup. Board Warner makes a setup for @ around $279.99. I spent nearly $300 May as well, right? Everything I put on it was new. Now I can maintain the performance of my injection, and keep it nice. Better Gas Mileage too! She runs TWICE as nice now. So I have 2 extra Injectors...