Starting problem...

[sx460]

Hello all, I have a '99 Silverado, 5.3L, 2WD, Ext Cab. It's a great truck and has performed well for a while now. The problem that I'm having now is with the truck starting. About 50% of the time, the truck fires right up. However the other 50% of the time, I have to crank the motor for a while before it will start up.

 

However, when it starts up either easily or hard, it stumbles for about the first 10 seconds. After that it runs great and has no problems. Any ideas?

 

I'm thinking of changing the fuel filter, cleaning/replacing the IAC valve, and checking the battery. Any thoughts?

 

Thanks guys

[phire]

I had the same problem in a Ford Windstar one time... Usually when it was cold outside it would do this exact same thing. I spent months trying to pin point the problem, testing everything I could think of and replacing what I thought was the culprit... I threw alot of money at the thing and still never solved the problem... I replaced distributor, cap, rotor, wires, plugs, ignition module, coil pack, throttle body, cleaned injectors, new ecm, fuel filter, map, maf, temperature sending unit (the one responsible for controlling the fuel injection system on this thing), new this new that... and still, it'd stumble in the cold...

 

Once it was warmed up or just warm outside, it ran like a brand new engine.

[RyanbabZ71]

Is this on cold start (after the truck sits all night) or after you turn the engine off (example running into a store and coming back out) and restart a short time later. I had the second issue and the Fuel Pressure Regulator was bad.

[RyanZ71]

Fuel pump, and or Fuel pressure regulator. Same thing happend to me.

[Supercop8100]

Try some top end cleaner also.

[sx460]

Is this on cold start (after the truck sits all night) or after you turn the engine off (example running into a store and coming back out) and restart a short time later.  I had the second issue and the Fuel Pressure Regulator was bad.

 

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Thanks for all your input guys. It seems to do it worse when the truck is fully warmed and has been driven. The problem usually does not occur when the engine is totally cold (like the first start in the morning), which is what I've found odd.

 

Can anyone make sense of why it happens when it's warm and not cold? Also, any advise as to how to go about solving the issue? Thanks much!

[phire]

I don't know I'm not really a mechanic but I had an 85 z28 Camaro that kinda did the same thing. Even though it was TPI (tuned port injection), it would still start hard when it was warmed up. I had to floor the gas pedal to get it to start within a reasonable amount of time. When it was cold, it'd fire right up. Almost as fast as I could turn the ignition I had to pull back to prevent it from grinding the starter...

[Blue2500CC]

I agree that the fuel pressure reg. is probably the problem. There is a small vacuum hose that comes off the top of the F.P.R., pull it a little bit after you had the truck running & see if there is fuel in there. If there is, replace it. After the truck sits, I guess the fuel evaporates & that is why it is easier to start. Just my experience from my truck & a couple buddy's trucks(not an expert). Hope it solves the problem.

Chris

[RyanbabZ71]

SX,

 

Sounds exactly like what happened to mine with the FPR. Do a search I had a topic going with some photos and part number for the regulator.

[RyanbabZ71]

Heres the link

 

http://www.gm-trucks.com/forums/index.php?...ssure+regulator

[sx460]

OK, thanks so far for everyone's help.

 

I just checked the vacuum tube. The first time I checked it, several drips of gasoline came out. It didn't rush out, but it did drip enough to get the FPR wet. I then tried to turn on the motor and had to crank it for a while.

 

After it was running for about 30 seconds I turned it off and rechecked it. No gas came out. So I restarted it and it fired right up. I then went out for a ~2 mile drive and came back. I rechecked it after the drive and it was moist but not dripping. So I restarted it and it fired right up.

 

So what I noticed is that the first time when fuel did drip out, it started hard. But then each time I checked it after that no fuel came out but it fired right up.

 

So, what do you guys think it is? FPR gone bad?

 

Thanks again!

[RyanbabZ71]

sounds like it. If i checked right away i didnt have any gas. Wait 10-15 mins then check.

[sx460]

sounds like it.  If i checked right away i didnt have any gas.  Wait 10-15 mins then check.

 

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I just pulled the vacuum line and fuel dumped out with a splash! HAHA, that should fix it. Going to the store tomorrow to pickup a new FPR. Thanks guys!

[RyanZ71]

You may need to go to a GM Dealer to pick up the FPR, should not cost all that much, maybe $60.00 or so. I don't believe it's a part that a normal parts store carries.

[sx460]

Just changed the FPR and all seems well. I'm going to keep an eye on it pretty carefully the next week or so. I thought I had bled the system well, but apparently not well enough because when I took off the FPR it shot fuel out all over me. Great! Word of advice: make sure to fully bleed the system before working on the FPR.

 

Thanks guys again!