Spinout007
Spinout007 GRM+ Memberand UltraDork
9/23/13 7:55 p.m.

Truck struggles to fire off the first time. When it catches it runs less than a second and then stalls. if I constantly play with the throttle in little increments I can keep it stumbling along, but if I just hold the throttle open a hair it dies. I can smell fuel, I can see injectors firing. When it stalls there is a loud click after a second or two. Almost like a relay closing or opening.

Here's where it gets fun. Dad swears it is a fuel pump. I'm swearing its an ignition module. Truck is a 92 TBI 350 C1500 2 wheel drive auto.

and........GO!

Kenny_McCormic
Kenny_McCormic SuperDork
9/23/13 8:03 p.m.

Easy to solve, put some gasoline in a spray bottle, remove air cleaner, see if you can make it run that way.

81cpcamaro
81cpcamaro HalfDork
9/23/13 8:33 p.m.

It may be the fuel pump. The Sunfire I had ran similar to what you describe when the fuel pump started to fail. It made about a mile before it finally quit. I would check the fuel pressure first.

On GM EFI, the ECM receives the signal to fire the injectors from the ignition system. So a bad module could stop the injectors from firing. Since it tries to run some, I would look at the fuel system first.

06HHR
06HHR Reader
9/23/13 9:19 p.m.

+1 on the fuel pump, that click you are hearing is most likely the fuel pump relay. The ignition control module failures I've seen on these trucks usually doesn't show up until the truck has reached operating temp, then they cut out. Letting the truck cool off for a few minutes "fixes" the problem until the ICM heats up again. Could also be the pick up coil in the distributor, but i'd check fuel first.

Streetwiseguy
Streetwiseguy UberDork
9/23/13 10:01 p.m.

Ignition modules work, or not. There is no middle ground.

Electric fuel pumps run, or don't run, mostly. There is very seldom a middle ground.

Your description implies it is lean, or the timing is late. Is the static timing correct, and was it set with the proper connector unplugged? Is the fuel pressure ok? 11-14 psi, IIRC. Is the map sensor ok? Is the EGR valve stuck open? Is the coolant temp sensor ok? Are the ground wires on the thermostat housing in good shape?

patgizz
patgizz GRM+ Memberand UberDork
9/23/13 10:24 p.m.

i had the same problem with my 90. it was that way for 2 weeks, then the ignition module finally puked. i've also had the same symptoms from a fuel pump putting out almost no pressure. until my recent avalanche, 88-94 tbi trucks were all i drove for work. i still have a couple. i had one freak run and drive with 1psi coming from the pump.

oldopelguy
oldopelguy Dork
9/23/13 10:32 p.m.

Sounds like my '90, replaced fuel pump relay, then pump, then it turned out to be a plugged fuel filter.

$4 for a filter is a cheap place to start.

alex
alex UberDork
9/23/13 10:46 p.m.

I'll tell you this: don't go for the fuel pump until you've exhausted other options or you're damn sure that's the culprit. It's in the tank, which you either have to drop or remove (or partially jack up) the bed to access.

The ignition module on my '88 C1500 acted weird before it died. Not the same symptoms, mind you, but it didn't just die and that was it. It taunted me for a week or two before it finally gave up.

But yeah, I'd also throw a fuel filter at it first. It probably needs one anyway. It's inside the frame rail basically under the driver's door. Have a catch pan for all the fuel in the line, and don't release the line with your mouth open.

06HHR
06HHR Reader
9/23/13 10:58 p.m.

Fuel filter definitely can't hurt. Check your fuel pressure, should be between 11 and 14. I had an ignition module die on I-75 south while towing a loaded 12 foot U-Haul trailer. It didn't just die though, cut out while running 70. Would restart while coasting in neutral. Finally died outside of a rest stop, coasted in and let it sit for a few minutes and it started right up. Did this again, got off on the next off ramp and found the nearest auto zone. Changed it out in the parking lot, no more issues for the rest of the trip. In my experience, GM ignition modules rarely just quit..

Spinout007
Spinout007 GRM+ Memberand UltraDork
9/23/13 11:11 p.m.

That's my experience with them. sadly I've rarely gotten just one that fixed it. I got to where i could change them quickly on the side of the road and kept a spare in the glove box. Not my truck, it's my sisters baby daddy truck and personally getting sick of being his on call mechanic. 5 minutes with it tonight and I confirmed what I had been thinking about it since I got the phone call last week. We'll see. I'll grab an ignition module and fuel filter on the way home from work tomorrow night. Had my sister not had her car trashed by a tree branch this morning I would be letting him fix it on his own. Now they're down to the vehicle they're borrowing from my dad.

david21
david21
9/24/13 12:19 a.m.
Strizzo
Strizzo UberDork
9/24/13 12:33 a.m.

The ford mod motors had similar symptoms to that when the egr valve stuck open, except For the having to vary throttle part. That part Linda points toward timing, as the vacuum in the manifold is coming up at that time in the first few seconds and varying the throttle would lower it, so if it's MAP driven timing it would see that or the vacuum advance in the distributor.

I'll agree that most of the ignition modules I've seen go bad do so when warm rather than cold.

david21
david21 New Reader
9/24/13 12:53 a.m.

This post has received too many downvotes to be displayed.


Spinout007
Spinout007 GRM+ Memberand UltraDork
9/24/13 7:33 a.m.

Wow.... now they're just rowboating threads... nice

yamaha
yamaha PowerDork
9/24/13 10:52 a.m.

Thats not a C1500........silly chebby.

Spinout007
Spinout007 GRM+ Memberand UltraDork
9/24/13 9:50 p.m.

The .25 squirt bottle says fuel related. Going to pop a fuel filter on it tomorrow.

Spinout007
Spinout007 GRM+ Memberand UltraDork
9/30/13 11:49 a.m.

Anyone that's interested, it was the fuel pump. After a weekend long scenario paintball game, I got a phone call to help put it in........LONG night, but he did 90% of the work.

Kenny_McCormic
Kenny_McCormic SuperDork
9/30/13 11:51 a.m.

If its a beater, the trick is to just cut a hole in the bed and then go to the junkyard and cut out a larger chunk for a patch to screw on.

06HHR
06HHR Reader
9/30/13 12:08 p.m.

Glad that you figured it out, sucks that it was the fuel pump but good that you didn't have to do all of the work. I've got to replace mine in the very near future, on occasion it doesn't pick up fuel when the tank is low. Not good when towing on the interstate at 70+ Anybody have any advice on what the best pump is for TBI trucks or does it matter because they are all made in China anyway

Kenny_McCormic
Kenny_McCormic SuperDork
9/30/13 12:15 p.m.

In reply to 06HHR:

Delphi, Bosch, Delco, Denso, whichever of those 4 is cheapest.

06HHR
06HHR Reader
9/30/13 12:22 p.m.

In reply to Kenny_McCormic:

Thanks, will more than likely go through the Ignition system too with a new distributor and coil. I'm pretty sure my fuel delivery issues are causing my uneven idle at times, but I don't think I want to trust a 22 year old pick-up coil assembly much longer.

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