Newbie with strange stalling problem

**repo-man** · 12-30-2008, 12:55 AM

Hello to all, and I hope you can help me out with this problem,

Ive been working on cars and trucks for years but dont have much exposure to the CPI system on later 90's 5.7s. I have a 1998 C1500 Suburban with 210k miles, formerly a Texas truck but been in Ohio for a little while now. It ran flawlessly until I went to go to work one morning. When I started it the truck kicked over, started, ran about 5 seconds and then died. Now it will start, run smooth for about 10 seconds then sputter and promptly die. Opening the throttle will also cause it to die. It appears to be running lean to the point of stalling out. It will restart right away and do the exact same thing. The fuel filter is new and the pump holds 55-65 psi as its supposed to. The fuel pressure doesnt dip way off starting and keeps up with the engine when running but the truck dies out anyway. If you keep spraying a little starter fluid into the throttle body it'll keep running until you stop, so something about 10 seconds after starting is causing the truck to stop getting fuel. I tried searching the forums a bunch but couldn't find anything that sounded like this.

Any ideas? Thanks!

**dwill3015** · 12-30-2008, 12:59 AM

Welcome to the site! Could you be having problems with the fuel pressure regulator?

**ct9a** · 12-30-2008, 01:05 AM

Welcome to the site! Ditto on the FPR.

**repo-man** · 12-30-2008, 10:08 AM

I suppose its entirely possible that its the FPR though I thought I read somewhere that they almost always fail rich, could be wrong, is there any way to test it? Am I correct in saying its on the injector "spider" under the upper intake or is it hiding somewhere else? Sorry, im used to TBI and MPFI, putting all this stuff inside the upper intake is foreign to me.

Thanks again!

**MrShorty** · 12-30-2008, 10:38 AM

The fuel filter is new and the pump holds 55-65 psi as its supposed to. The fuel pressure doesnt dip way off starting and keeps up with the engine when running but the truck dies out anyway. If you keep spraying a little starter fluid into the throttle body it'll keep running until you stop, so something about 10 seconds after starting is causing the truck to stop getting fuel.

This doesn't seem like a regulator problem to me. I assume the first statement means that it holds pressure even after the pump shuts off?

The fact that it runs on starter fluid does indicate a fuel problem, though. Because the fuel system seems to be delivering sufficient fuel to the injectors, it makes me think there's a problem with the injectors themselves. Maybe dirty. I know GM has had quite a few problems with the stock "poppet" valves, to the point of redesigning the fuel body to use real injectors (the so-called upgraded spider or Multech II I think it is).

Any codes in the computer? If you have access to a scanner it might be useful to see if there are any engine parameters that seem out of whack 10 s in. I haven't looked at mine, but is there a way to get a noid light on the injector wiring to see if the injectors stop getting a signal?

**bassalive** · 12-30-2008, 10:57 AM

Yeah ,I would check codes first and go from there.

**repo-man** · 12-31-2008, 01:02 AM

By it holds pressure I mean as long as the key is in accessory/run or start (the pump has power) the pressure never goes below 55psi. Any non-scanner ideas on how to test some of these components? Im trying to get ahold of one but in the meantime all I have is my trusty Fluke digital multimeter.

**MrShorty** · 12-31-2008, 10:57 AM

In that case, how long does it hold pressure after the pump shuts off? One failure mode for the FPR is for the diaphragm to rupture, allowing umetered fuel into the intake. A severe enough leak could "flood" the engine and cause it to stall (though I don't think it would continue to run on starter fluid if this were the case). For comparison, I had a pressure gauge on my '98 the other day, and it held 50+ psi pressure for at least 10 minutes, and still had 30+ psi in the fuel system an hour later when I took the gauge off.

Because there are numerous possible culprits, I would get codes before trying to test the entire system. For ideas on testing some of the sensors, you can look through any DIY repair manuel (autozone.com has a free electronic version of Chiltons available if you don't like print manuels).

It's not as good as having your own scanner, but, in the States other than Ca, many parts places (like Autozone) will pull codes for free.

**repo-man** · 01-01-2009, 05:48 PM

My pressure gauge didnt hold pressure that long, but does hold pressure for a while (i think the gauge was leaking slightly however, its made from pipe fittings and a 100psi gauge) I would just take it to a parts place and have them do it but its undrivable as it is. I think some of our autozone's and murray's around here will rent a scanner so im going to check into that tomorrow, hopefully it'll tell me something useful. Worst case scenario partsamerica has the conversion spider on sale for about $300 if its an injector thing.

**retired** · 01-01-2009, 06:30 PM

You have a major vacuum leak? Have someone start it and spray some carb cleaner around the intake and look for a rise in the rpm and there you will find your leak.