95 Lumina APV 3.1L - not starting - diagnosed my butt off

[xphire]

Okay, so we've already established that the van doesn't start. Just for the sake of easy reading, we're working on a 1995 Chevrolet Lumina APV with a 3.1L engine. Now that that's out of the way, here's the problem... It won't start! How do I fix this? Just kidding, I've done quite a bit of diagnosing on my own and now I need some help. Here's what I've done so far:

- Replaced the coil pack.
- Replaced the distributor.
- Replaced the ECM.
- New plugs, wires, cap, rotor. Great spark now.

So, now that we have great spark, we are no longer getting any fuel. I don't know if it was the spark or the fuel that was causing it to not start to begin with, because sometimes it would start and other times it would not. Was mostly just random and had the hardest time starting while it's cold out... So maybe it was always sketchy about getting fuel while cold... Now it won't start period - warm or cold. Okay anyways, now that we have great spark again... I've done this:

- Tested the 2 injectors (TBI) with a 12v wire & ground, they tick loudly as they should when voltage is applied. No such ticking is heard while cranking.
- Tested for proper fuel. Plenty of fuel from the pump and plenty of fuel from the return line under cranking so pump and relay are good.
- Tested for voltage at the injectors during cranking, the voltage spikes under crank. Voltage is negligable when not cranking.

So, without spending $200 for new injectors, I'm guessing this is probably going to be an electrical problem? Because the injectors tick nice and loudly when voltage is applied and they're getting voltage like the ECM is trying to tell them to open up to release fuel... But I really don't know a) how I'd go about diagnosing and finding an electrical problem. and b) I find it highly unlikely that both fuel injectors would decide to up and quit at the same time...

Anyone have any ideas on what else I could possibly diagnose and test?

[maxwedge]

Check the injector fuses first.

[richtazz]

The ECM gets it's RPM signal from the ignition module that's in the distributor through the pick up coil. Even if you bought a re-man distributor, there is a chance that the module and/or pick-up coil is no good. Take the module out and have it tested at Advance or Auto Zone. Make sure they run the test enough times to get the module hot. Also, check the pick-up coil. The two wires that come out of it should register a resistance of 500-1500 ohms. Any more or less and the pick-up coil is bad. You say you have fuel, but you never said what your pressure reading is. It is possible to have fuel present, but not enough pressure to allow the injectors to fire. Fuel pressure should be 9-13psi. You may want to check the fuel injector resistance also, it should be 1.2-1.6 ohms.

[xphire]

Originally Posted by richtazz

The ECM gets it's RPM signal from the ignition module that's in the distributor through the pick up coil. Even if you bought a re-man distributor, there is a chance that the module and/or pick-up coil is no good. Take the module out and have it tested at Advance or Auto Zone. Make sure they run the test enough times to get the module hot. Also, check the pick-up coil. The two wires that come out of it should register a resistance of 500-1500 ohms. Any more or less and the pick-up coil is bad. You say you have fuel, but you never said what your pressure reading is. It is possible to have fuel present, but not enough pressure to allow the injectors to fire. Fuel pressure should be 9-13psi. You may want to check the fuel injector resistance also, it should be 1.2-1.6 ohms.

Well I had a spare known good module and also the old one and a new one I bought for the old one... so I have a total of three modules... Tried all three, stilll the same symptoms. Not sure about the pick-up coil, but the chances of both being bad? And the resistance on the coil should that read 500-1500 ohms while cranking or at all times when the ignition is on?

No fuel pressure readings because I don't have a gauge. I think I'll set out to buy one today, they're cheap enough... Are they generally universally fitting? I was browsing the web and noticed most of them were for specific cars...

[richtazz]

The ohm spec is with the pick-up coil disconnected, and the multimeter across the two terminals. You should also try wiggling the wires while testing to make sure it doesn't have a break that is making intermittent contact. Actron makes a nice, inexpensive fuel pressure tester ($30 range) that is carried by both Advance and Auto-zone. Get the fuel pressure reading, and also check the injectors themselves for resistance.

[maxwedge]

Rich, that tester may not work on his TB unit I don't believe there is a rail test port.

[xphire]

Originally Posted by maxwedge

Rich, that tester may not work on his TB unit I don't believe there is a rail test port.

You're right, now that you mention it... It doesn't really have a "fuel rail." It's more like a one single peice unit that houses the fuel pressure regulator and the 2 injectors all in the same unit. The fuel routing goes from the tank directly to this unit which is about the size of 2 fists put together and there is no special port for a pressure gauge. I just thought that maybe I could hook it directly into the main fuel line before it hits the regulator and gauge it... The fuel line goes directly into the FPR, so no port.

Although, let's say that I was a few psi too low, I should at least get a LITTLE fuel shouldn't I? I mean, at least enough to make the engine cough a little bit while cranking? I get NO fuel through the injectors. I'm going to go out and get those resistance readings right now, though.. I haven't had a whole lot of time lately to work on this thing.

Oh, someone also suggested that it may be the crank position sensor... They did a fairly good job of explaining its role in running an engine and I thought maybe it could be that... But I thought I also read somewhere that the crank sensor is also responsible for spark??? Dunno about the last part, but if it's true then the crank sensor should be fine since the spark is wonderful.

[richtazz]

your engine doesn't have a crank sensor. They are referring to the car engine that is distributorless. I was incorrect, as your van doesn't have a schrader valve, so you'll need a more involved pressure tester for your vehicle, sorry!

[xphire]

Originally Posted by richtazz

your engine doesn't have a crank sensor. They are referring to the car engine that is distributorless. I was incorrect, as your van doesn't have a schrader valve, so you'll need a more involved pressure tester for your vehicle, sorry!

Well then that'd be why I couldn't find the crank sensor. :P

[xphire]

Originally Posted by richtazz

The ohm spec is with the pick-up coil disconnected, and the multimeter across the two terminals. You should also try wiggling the wires while testing to make sure it doesn't have a break that is making intermittent contact. Actron makes a nice, inexpensive fuel pressure tester ($30 range) that is carried by both Advance and Auto-zone. Get the fuel pressure reading, and also check the injectors themselves for resistance.

Okay, well the two wires that come up from the pickup coil into the ignition module read 745 ohms with both the key turned on and off. I take it that's a good thing? What else do ya think I could check?

I doused the intake with ether earlier to see if it would start spitting out fuel if the engine got cranking good enough but, no such animal. It wouldn't run without ether (or manual gas being sprayed in.)


EDIT: Okay, so it was two things... The ignition module that came w/ the reman distrib was bad and also I had one of the wires crossed on it... That's why I wasn't getting fuel... I'm glad you told me that the ignition module was responsible for telling the ECM the rpms! So, now that I have fuel ... I still can't start... Getting spark though... Probably a timing issue maybe? Like a dummy, I forgot to mark the distributor when I pulled the old one out so... Is there any easier way to do this aside from gradually turning the distrib until it shows signs of life or do you think there may be something else, too? I think the way I had it though was pretty close because I remember the way the ign mod sat in there and also the where the #1 wire was.

Anyhoo, just a recap... I replaced distrib, ign mod, coil pack, plugs, wires, cap rotor, ecm, also put new filters on the injectors, new gaskets, o-rings, etc. It doesn't take much to run a car, what am I missing?

[richtazz]

Bring the timing mark to TDC, and make sure that the #1 cylinder is on the compression stroke (the crank turns twice for each turn of the cam, so the timing mark on TDC will also hit on the exhaust stroke on cyl #1). Mark the distrubutor body where the #1 cylinder tower is. Take the cap off and make sure the distrubutor rotor is pointing at your mark.

[xphire]

Originally Posted by richtazz

Bring the timing mark to TDC, and make sure that the #1 cylinder is on the compression stroke (the crank turns twice for each turn of the cam, so the timing mark on TDC will also hit on the exhaust stroke on cyl #1). Mark the distrubutor body where the #1 cylinder tower is. Take the cap off and make sure the distrubutor rotor is pointing at your mark.

Alright, so the timing should be great now... However, I just noticed something really really weird... It's getting PLENTY of fuel but it's still not turning over... It is turning over SOMETIMES but not all of the time. When it's running, it looks like fuel is spraying way too much into the TB. It looks like a shower inside the barrel. This also causes it to diesel for a few seconds after the engine is turned off. So, I thought maybe it would be the fuel pump relay sending too much fuel, but it doesn't always start and it seems to always be getting plenty of fuel... I'm out of ideas...

[tapcola]

when it will not start- does the check engine light come on when you turn the key? and the fuel relay clicks? If so, you have the same problem as mine. I have had it to 3 different garages and changed parts on it trying to figure it out. Believe it or not what starts it is putting a heater or a hairdryer under the dash for a few minutes and the check engine light will turn on and it will start. I think it has something to do with the computer getting moisture or the cold affecting it electronically. Hope this helps and might save you some money.

[xphire]

Originally Posted by tapcola

when it will not start- does the check engine light come on when you turn the key? and the fuel relay clicks? If so, you have the same problem as mine. I have had it to 3 different garages and changed parts on it trying to figure it out. Believe it or not what starts it is putting a heater or a hairdryer under the dash for a few minutes and the check engine light will turn on and it will start. I think it has something to do with the computer getting moisture or the cold affecting it electronically. Hope this helps and might save you some money.

the check engine light comes on and the computer is brand new and was tested so it's working properly.

[Gill YM]

With my 1990 APV, I had this prob too. It turned out to be as simple as not being "earthed" properly!
Once that was done, it was brill, started first time every time.