[FIXED] 1994 Chevy Suburban C1500 - cranking, no start

1994 Chevrolet Suburban 5.7L Automatic 2-Wheel Drive; 366,000 miles on vehicle; about half that on the drive train

My son was driving the truck and it was running fine. After about 30 miles of highway driving, the truck completely stalled out while stopped at a traffic light and would not restart. The engine would crank fine but it would not fire at all. He attempted restart numerous times with no success.

We had the truck towed back home so I could have a look at it. At my garage I also attempted to restart it. It would crank fine but did not fire at all. I could hear the fuel pump prime when I would turn the key to the On position. I also opened up the throttle body and attempted to start while spraying starter spray into the throat of the throttle body. Again, it cranked fine but it did not fire at all. So then I thought I would check for spark. I hooked a spark checker to cylinder #1 and it indicated that I was getting good spark. After the initial test of the spark I thought I would repeat the test. When I cranked the engine that time there was a slight indication that it wanted to catch and fire. But it did not start. When I repeated the spark test a third time the engine cranked but did not start and did not fire at all but again the spark checker did show I was getting spark. By then it was late and I decided to to come back two days later on Saturday morning to continue my tests.

On Saturday morning I thought I'd do a quick compression test. So I pulled the spark plug from cylinder #1. The plug itself looked okay and the gap was fine. I installed a compression gauge and lo! and behold! the engine started right up. The compression reading was 132psi which is a little below spec but the engine has almost 200,000 miles on it so that did not concern me. I was a bit baffled as to why the engine is now suddenly starting. I reinstalled the spark plug and connected the wiring and started the engine again and it ran fine. So it seemed to me at that point we have some kind of intermittent problem (I know, call me Captain Obvious!). I did a little poking around. I noticed that the distributor cap was a little bit loose so I tightened down the screws about 3 turns each. The distributor cap is now tight and secure. I doubt that the distributor cap was the problem. But at the same time, the truck is running now. I've driven it 30 miles with no problems. The only other thing I can think of that it might be is maybe the computer is getting a little schitzy.

What I am minded to do right now is just drive the truck around town as usual and see if it acts up again. If it does, I'll probably have a look at the computer and its connections. Any ideas or suggestions that you guys might have would be appreciated.

Just thinking out loud here... How strong was the spark you found with your tester? 1/2" gap? I was thinking about an ignition coil that's intermittently failing to give strong enough spark. OR the distributor rotor is shorting to the shaft, resulting in weak spark and fouled spark plugs.

Another thing to look for would be the injectors spraying during the crank no start. I dunno that lack of fuel is your problem (since adding alternate fuel didn't help), but it would tell you something about the state of the PCM. If it's pulsing both injectors, and fuel is spraying out, then you can probably eliminate fuel and the PCM as potentials.

Thank you, Tyler. The truck is running fine, I have been driving it for two days now, and I am out of time for looking at it anymore. This may well have to be revisited , as I just doubt that the distributor cap was loose enough to produce the symptoms encountered.

Thanks again!

Pop

Well after a week of running fine, the truck broke down on my son again today. Injectors are spraying fine while cranking, distributor cap is still tight. I am going to look at the spark situation, but that will have to wait for the weekend.

Thanks for the update! Good to know about the injectors, makes me feel better about the PCM and powers/grounds.

Had the truck towed home again, and once again after the engine had fully cooled down, the truck started right up. I think I am going to check the quality of the spark, and see if there is any change as the engine heats up. That, and a. Usual inspection of the ignition system is all I can think of to do at this point.

Does this 1 have the pickup in the distributor Under the rotor? I'm not sure how to test it other than put a heat gun or blow dryer on it and see if you can make it die .they were pretty common causes of dieing hot and starting cold

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sounds like to me you have an ignition control module shorting intermittently or you have a shorting igniter ive experienced this on many 5.7 chevys

I left the truck running in my driveway for two hours, it did not stall out. I did notice that the two wires ( a pink wire and a white wire) were resting on an edge of intake manifold between the coil (where one end of the wires' connector plugs in) and the base of the distributor (where the connector with the other ends of these wires plugs in). The insulation on each of the wires is burned where they were resting on the edge of the manifold. Though not burned all the way through. My guess is that with heat and vibration high resistance resulted, interrupting the spark. I am going to fix these wires so I can at least eliminate these as a variable.

I very similar issue with a 1999 GMC suburban 5.7L. It started initially as a crank no start occasionally. This went on for about 6 months. Now it is a complete crank no start. Engine has 147000 on it. I have done a full ignition tuneup. Plugs, wires, distributor cap, rotor. I even went so far as to change, ignition coil and control module. I have spark at all cylinders and 55-58 psi fuel pressure. I have a feeling since it was intermittent to start with, it is going to be some corroded connection problem. I also tried starter fuel down the throttle. I am hoping what you find may help me.

Sbirchmeir your 99 is a vortec the 94 is a tbi you can start a new thread for help on your 99 , when it is not starting try a jumper cable from the battery ground post to either the body or the frame and see if that cures it I've had the same issue from bad ground straps and jumper cable was easy diagnose

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There is a possibility that the ICM is not sending it's 5 volt reference signal back to the ECU to fire the injectors. ScannerDanner has a video that explains how this works and how to troubleshoot it. I can't think of the video title, but it is in the ignition topics.

I can see the injectors spraying into the throttle body during the crank/no start. Also, the engine always starts again once it cools all the way down. I repaired those wires in the pic, and have put the truck back on the road. If it makes it at least a week without stalling out, I am calling it a fix.

Get a new control module keep it in the glove box with a, I believe, 1\4 inch nut driver. Or what ever size takes the cap off and unscrews the control module. When it dies swap em . If it starts right up, well,that was the problem.
P.s. keep the old one in the glove box. If it ever happens again,you know it's good for about 30mi.

Finally was able to replicate the problem in my garage. I took a closer look at the injectors. It seems to me they are spraying too much fuel. They are not producing aerosolized spray, but rather they produce heavy droplets and even liquid gas that pools up on the throttle plates. I disconnected the electrical connectors to the injectors to see if the engine would fire with the throttle wide open using the gas that was already in the intake. The engine fired and ran for about 30 seconds.

So, it would seem, the problem is the injectors. Can I repair the injectors, or do they need to just be replaced?

Hey, progress! Nice job catching the injector issue.

popoften wrote: So, it would seem, the problem is the injectors. Can I repair the injectors, or do they need to just be replaced?

I was actually wondering about low fuel pressure, and how that might produce the injector spray (or lack thereof) that you noted. Without enough pressure behind them, the injectors can't produce the normal spray pattern they should.

The trouble is measuring fuel pressure... I don't think these TBI systems have Schrader valves, so you may have to get a gauge in-line with the pressure side. 9-13 PSI with the engine running is what you're looking for. A deadhead test might be a good idea, too. I would expect to see at least 25 PSI, preferably closer to 40 or 50 PSI.

They make a tbi fitting adapter usually in most pressure kits but also available seperatly at summit or jegs and such. The injectors just sit in that pod sealed by orings. The fuel enters the pod from the side ,there's a hole on the side of the injectors. The fuel pressure is just held in by the orings,so when they get old and dry and crack or harden the fuel seeps by. Yes, easily rebuilt with tbi rebuil kit. Might as well take it off and redo it and change the pressure regulator and internal filter. It's not that hard.

Time for me to work on this problem has been even more intermittent than the problem itself. Now that the truck has been sitting in my driveway for a month, I have finally had a chance to check the pickup coil in the distributor. The insulation on the white and green wires was heavily cracked, every quarter centimeter or so, and the winding itself was in really bad shape.

I replaced, and drove the truck almost 200 miles today and it is running fine.

Thank you for all your insights, guys!

Here is a pic of the old pickup coil.

Thanks all!