Won't Start

Gary in La · August 28, 2004

A friend of mine has a 1999 Chevy Silverado with 5.3? engine.

Truck will start cold and run fine. Once the engine is hot and you turn off the engine, it won't start.

Lift the hood, let things cool off and it will restart and run fine. This repeats everytime it is turned off.

The local dealer has reprogrammed the computer, and even reprogrammed the keyless entry as the security light remains on when you are driving it.

Fuel pressure is ok, cylinder compression is ok.

If it's electronics, both of use are way too old to know how to fix it.

I don't know what if any error codes showed when it was checked by the dealer.

So far $500 spent and the thing still isn't right.

Any ideas would be appreciated.

Thank you

GMCSierra04 · August 28, 2004

Sounds like you could have a vapor lock issue. This would allow you to start the truck with no problems when its cold but as soon as the engine gets hot, and the fuel in the fuel rail gets to a certin temperature, problems happen. A check for this would be to hook up a fuel pressure gauge and check the residual fuel pressure in the lines about a min. after you turn the truck off. I can't remember the specs for residual pressure but it shouldnt be hard to find. What could be happening is that when the truck is shut down the fuel psi drops down to a point where there is empty space in the lines or most likely the fuel rail. With the hot engine, the fuel begins to boil and when you go to start it up again you get nothing. This could be caused by a leaky injector, fitting, the fuel pump's anti drain back valve or basically anywhere. If you dont see fuel dripping from any where then begin to look into the injectors and work your way back until you have found the problem. Hope this helps your friend out, good luck and let me know what you find.

ronterry · August 29, 2004

I've also seen leaky regulators, bleeding right into the vacuum hose.

Another thing that pops into my head is EGR. Make sure it's not sticking when hot.

Man 'O' man what I would give for a Tech II:D well, not 2 or 3 grand at least

You can cycle the EGR valve with a push of a botton, and at least rule that out.

Ron

GMCSierra04 · August 29, 2004

I'm not sure a leaky diaphram would cause a no start when its hot. Yes it would lose residual pressure when the engine is off but the fuel pressure regulator vacuum source is manifold vacuum. I could see harder starts until the vapors in the line would get drawn out back into the engine b/c during cranking about 13"Hg is present and with operating pressure of the fuel system of about 55 psi, it would over come that problem. Now he would getting a very rich A/F ratio when idleing but during cruise speeds and WOT situations it wouldn't be very noticible. Even on the 5-gas analyzer you would see elevated CO during idle but as soon as you gas it up they would drop down to normal levels, if thats the problem.

If the metals could expand enough in the EGR valve then that might be possible but check and see if your engine is EGR equipped. MY 04' Sierra doesn't have an EGR, just look on the emissions sticker under the hood and you'll know. I think the eairlier 5.3's had the EGR though. Bi-Directional controls are a techs best friend! You can do function tests with the Snap-On MT2500 also, it will not get as big of a data stream as the Tech II but you can deffinetly make some $$$ using it.

95whtZR2 · August 29, 2004

Does the starter engage when you say it won't start? My starter on an old truck had the exhaust too close and it ended up not being able to start when it got hot. Just a thought...

Tom

karld · August 30, 2004

My truck had the same problem. It turned out to be the fuel pressure regulator. If you pull the vacuum line off the regulator and fuel pours out,the regulator is bad. Takes about two minutes to replace. Hope this helps!

budhayes3 · August 30, 2004

Same here....fuel pressure regulator. Pulled the vacuum hose off and fuel poured out. Took about 2 minutes to replace on my lunch hour and I didn't use any tools. The little o-ring stayed in the fuel rail when I pulled the regulator out, so I straightened a staple from the recipt to use as an angled pick and fish it out.

Gary in La · August 30, 2004

Here's the answer to the starting problem. My friend had a bad security system that was sending a signal to shut off the fuel(like the truck was being stolen).

Dealer #1 installed new security system but installed software on top of old program. Same stuff, new system is told by old program that wasn't removed, to shut off fuel.

Dealer #2 removed old security system profile and installed new profile. Now truck runs.

If this makes sense, great, if it sounds like bs, that's what the dealer told my buddy.

Thank you guys for the help anyway.