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Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 29523
Experience:  GM Grand Master Technician 2007. 14 year experience.
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99 GMC Yukon 5.7 votec, starts a bit hard and stumbly, but

Customer Question

Customer: 99 GMC Yukon 5.7 votec, starts a bit hard and stumbly, but starts. It runs smoothly for about 1/2 - 1 full second, then shuts down abruptly, as if ignition were turned off. I can repeat it several times, same result. Then, everything is the same, a bit hard to start, then runs smoothly, and does not shut down at all. I can turn off and on several times, no problem. Next day, its back to starting hard, running smooth for a second, then suddenly shutting down. Thanks
JA: Thanks. Can you give me any more details about your issue?
Customer: Car ran fine before this. It has been damp and cool (35 degrees), but once it started I sprayed water on the coil and cap, thinking the dampness might be causing some acring etc. Spraying water had no effect, so it doesn't seem to be a coil or cap issue.
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Submitted: 1 year ago.
Category: GMC
Expert:  Gm Tech (Cam) replied 1 year ago.

Ih there, I am Cam. Can I get your first name please?

MY first thought on this is the fuel system. Too start with, can you tell me if you have checked the fuel filter and fuel pressure?

Customer: replied 1 year ago.
filter replaced not long ago, pressure looks ok, stays up even after the engine dies.
Expert:  Gm Tech (Cam) replied 1 year ago.

what pressure do you get then please/

Customer: replied 1 year ago.
58psi, a bit low I know but it has been that way all along, for maybe a year or so. This problem is new.
Expert:  Gm Tech (Cam) replied 1 year ago.

Is that with the engine running or the engine off and the pump running?

Customer: replied 1 year ago.
Both I had the gauge propped up so I could see from drivers seat.
Expert:  Gm Tech (Cam) replied 1 year ago.

So that is a bit low, and possibly an issue. I think though your main issue is the spider assembly. With this age of vehicle and those systems being what they are, they are VERY common for issues with the injectors and leaking regulators. I would suggest you replace the spider assembly but upgrade it to the new style MPFI.

Expert:  Gm Tech (Cam) replied 1 year ago.

On second thought, I would put a cap and rotor on it just because first. The water test does not rule it out.

If that does not then do the spider.

Customer: replied 1 year ago.
Ran great until this happened. When it happens, it runs great for a second. A while later it will start and run fine. So if the spider is an issue, it sure has a funny pattern of failure. does it not seem much more like a deliberate thing, an ECM thing? Also, the second or half second that it runs seems to be exactly that same amount of time, and when it shuts down, it is absolute, like the key were turned off. By the way, I experienced the VATS system a year ago when key assembly was replaced. This is just like that, except I do not get the blinking SE light. I've had a stored code for months now, if this issue was a VATS deal, would I still get the blinking SE light (I don't seem to have a security light on this vehicle)
Expert:  Gm Tech (Cam) replied 1 year ago.

The security would not make it run funny then stop, it would simply stop so I have my doubts that’s it.
I would take a few minutes and check the wiring that runs down the passengers front of the back to the crankshaft sensor and see if there is any damage to wiring, loose terminals and such.

Customer: replied 1 year ago.
It doesn't run funny. It runs for 1/2 second smoothly, then stops dead. It repeats that same pattern exactly. I will check wiring when I get back out there.
Expert:  Gm Tech (Cam) replied 1 year ago.

OK, after that, lets try a theft relearn.

Turn the key on and attempt to start the car, It may crank, it may start and stall or it may do nothing at all, this is fine, still cycle the key to start then release the key back to run.
Wait 10 minutes with the key in run. The passlock light should be flashing and the DIC will say "Service Vehicle" or "Security" or have a picture of a car with a lock during that 10 minute span.
After 10 minutes has passed, turn off the car, count to 10, and try to start it again and release the key back to run.
Wait another 10 minutes.
After 10 minutes, turn car off 10 seconds and try to start again and release the key to run.
Wait another 10 minutes.
After 10 minutes, turn car off 10 seconds and try to start again.
It should start up this time. The passlock has been learned.

During this process, turn the fans off, radio off and cycle the headlights off so the battery will not go dead. If needed, use a battery charger.

Customer: replied 1 year ago.
I'll try that procedure next time it fails. It has started the last couple times I tried today. Failures so far have been first time I tried to start it that day. Once it starts and continues to run, it seems to be ok until the next day. So I will try procedure at next failure, probably tomorrow.
Expert:  Gm Tech (Cam) replied 1 year ago.

Please bookmark this page so you can easily navigate back to it so we can continue the discussion. This is done by pressing (CTRL D on PC and CMD D on Mac). You can reply at any time for follow up information regarding this issue, even after you rate the site and I will reply.