Intermittent Starting Problem

BlackTaz · May 16, 2004

My 99 Yukon with the Vortec 5.7L V8 is flaking out. Twice in the past couple of months, I can't get it started. I crank it over and it fires up, but runs for only a second before it dies. I can hear the fuel pump by the rear wheel well making noise, so I know it's running. I think there's another fuel pump near the engine... could it be that one's not working right? It looks like it will be a bitch of a problem to diagnose since it doesn't happen consistently.

It seems like it might be a fuel problem, but it's only happening every once in a while. The first time it happened, I tried starting it about 20 times (really!)... finally, it started and then has run fine and started reliably... until today. I tried starting it about 10 times today and it wouldn't go. I tried to start it again, 8 hours later, and it started right up, the first time.

Both times I've had this problem, it's been after it's sat nearly a day, so it was stone cold. I need to get this fixed before it leaves me stranded somewhere!

Anyone else have experience with this type of intermittent starting problem?

Thanks!

GMCTech · May 16, 2004

I'm not sure what your problem may be, it's possible that you have a security issue in your truck.

You may have to have it scanned for codes or at least try to get a scan tool that you can watch data with when you have the problem.

By the way you don't have another pump by the motor, just the one in the tank.

Hope this helps.

GMC_MTR_4X4 · May 16, 2004

on my 97 z71 5.7 I had a problem like that I left the truck overnight somwhere then I went to start it in the morning and it turned over a buncha times then I stoped tried it again and started up fine but it was turningover for 30 seconds total and never started up. its happened twice now im not sure what caused it but it seemed like it was starving for fuel or maybe it wasnt getting proper spark. by the way your truck has a fuel filter by the pump and another by the motor but only one pump.

BlackTaz · May 21, 2004

Thanks for the help, guys... and for clarifying about the fuel pump.

I actually grabbed the manuals and read through the diagnosis section (managed to find some time for that). I think you're right, GMC Tech, my money is on an intermittent problem with the security (Passlock) system. My life if full of intermittent problems

According to the manual, if the security system thinks you are using the wrong key, or otherwise tampering with the ignition lock cylinder, the security light will flash and the fuel delivery will be disabled. In my case, because I was focused on starting it over and over, I may not have left the ignition in the "on" position long enough to notice if the security light was flashing. Next time, I'll be on the lookout for that. Then, I'll know I just have to wait 10 minutes and try again.

Anyone else have trouble with intermittent problems with the security system kicking in? If that's what's going on with my truck, is it most likely that I have to replace the lock cyclinder or is it something else? Maybe I should just switch keys?

Thanks!

May 21, 2004

Could still be a fuel delivery problem too. Next time it happens, when you go back to "on" to look for the security light, leave it there for about a minute without cranking. Then crank it, if it starts you may still have a fuel pump problem and low initial fuel pressure.

just a thought

99-2door · May 21, 2004

OK, you guys are describing 2 different scenarios

1st: Trucks starts as normal runs for only a few seconds then dies. This is a PASSLOCK II issue, either a faulty passlock trigger, wiring issue or an unrecognized PASSLOCK resistance. You will need someone with a TECH 2 to

fix this issue.

2nd: Truck occasionally will not start. Everything powers up as normally, including fuel pump. Starter cranks, but motor will never start up and run.

This is a faulty igniton switch. The electrical switch is made of plastic and wears out quite often. Take the cover off the lower steering column and wiggle the big wire connection at the switch to see if you can cause the truck to start/not start. Replace the switch, problem fixed.