1996 5.7 Tahoe Trouble Starting...Once Warmed Up
 

Hey everyone, I’m looking for some help. I have a 96 2 door 5.7 Tahoe, and I’m having a problem I can’t seem to fix I was wondering if anyone has had the same or similar problem. The truck has 191k on it but has been taken care of extremely well. The problem I’m having is the truck starts up fine after sitting over night (cold), but once the truck has warmed up and is turn off it doesn’t want to start back up; the only way to get it started is to press the gas pedal down to get it started. I have don’t some work to the truck to fix the problem but it still does the sameting<O:p</O:p

I have replaced the bank 1 O2 sensor, which the SES light was on for(which I know isn’t the problem) SES light is off and the trucks not throwing any codes; but acting the same. So I replaced the fuel filter no luck, although the filter was dirty.<O:p</O:p

So I’ve read on several forums the fuel pressure regulator is usually the problem so, I ripped the upper intake manifold off to replace it, well once the Upper Intake was off I notice there was gas lying in the back of the manifold mostly on the passenger side, and directly under the spider injector on the driverside. So I said the hell with it, It’s apart and it looks like the poppet valve maybe leaking or injectors, so I just bought the MFI conversion kit from GM and installed it along with a pretty good plenum and manifold cleaning as well and new gaskets, put the truck back together…..Truck Starts right up, I’m Happy YES problem solved CHEERS, turn the truck off does the exact something. So at this point I push the gas pedal down start the truck back up, pull it out of the garage and take it for a long ride; the truck is running great, so I get it home and turn it off thinking this may help it in some way, turn it off and try to start it something turns over nothing, press the gas pedal down starts up rough and then comes to life. Sigh, so by now I’m ready to rip the gas tank out in a hulk:D rage and throw the fuel pump across the street.<O:p</O:p

So now I have taken the gas tank off the truck calmly, bought a new fuel pump and filter. The fuel filter is installed (the old filter was clean when removed but replaced anyway) so I pulled the fuel pump and nocitced that the gas lines on the top of the fuel pump assembly are pretty corroded. So at this point the gas tank is out of the truck and I’m waiting on parts to replace the entire fuel pump assembly and put the truck back together with my finger crossed this is the answer.
My question I guess is when I reinstall the tank and fuel pump is this going to be the last of this problem? It just puzzles me that the truck runs great once it’s started and starts fine when it’s cold like there’s nothing wrong. So if you have had this same problem with your truck fixed it yourslef or had it fixed PLEASE reply, I just don’t want to get the tank back on the truck and start it up with a big smile then turn it off and have it not want to start. I will update this post once the fuel pump is installed to let everyone know if that solved it. I just don’t want to take to a mechanic; I’ll just feel defeated if I can’t solve this problem in my garage myself.
<O:p</O:p
I can post pictures of what the upper intake manifold looked like before and after I installed the MFI system along with pictures of the fuel pump. Oh and the gas tank has pretty much no sediment inside it almost looks new inside.

http://i57.photobucket.com/albums/g2...boy/Tahoe1.jpg
http://i57.photobucket.com/albums/g2...boy/Tahoe2.jpg
Thats the Upper Intake Ill take pictures of the Fuel Pump is you guys want.

How does it idle when it is running? Does it sound or smell like it might be running rich? If it starts up fine when its cold it sounds like the fuel system components are fine. Maybe getting too much gas while running causing the plugs to become saturated in fuel? Or maybe its not the fuel at all maybe the plugs aren't lighting the fuel properly? Just some ideas, I may be way off base here.

maybe the coolant temp sensor or tps,will it start at all when warm without steping on the gas

Sean
97 4x4 burb

The truck idles fine, the only time it idles rough is when I have to give it gas to start; but once it starts up and runs for a few seconds it idles normal.
The truck sometimes starts when warm without given it any gas, but its barley running, and once it runs like that for a few seconds it idles normal once again.
I’m waiting for the fuel send unit to come in today so I’ll have the truck back together later on today. I’ll update this thread once it back together to let everyone know if the problem is still present.
If this doesn’t solve it, the next think I’ll be going for the throttle body sensor; it’s pretty much acting like it’s flooded. So I’m thinking the sensor maybe letting fuel continue running after the truck is off, and the only reason it starts when it’s cold is that the fuel as had time to dry.

No luck the truck is back together, start about 5x's normal once the ne fuel sending unit and fuel pump were installed. I pulled it out of the garage to get changed to go get gas but as soon as I shut it off it started doing the samething.

So now it has;
1. MFI system
2. Bank 1 O2 sensor
3. Fuel Sending Unit
4. Fuel Pump
Still no Luck

Tomorrow I'll pull the plugs and replace them; and after that I guess it going to the GM dealer since I can't figure it out. Thanks all I'll keep you posted.
Paul

So get this... dropped the truck off last night at GMC dealer they call me this morning to tell me the truck needs a fuel pressure regulator for the low cost of 800 bucks you can have one installed in your truck to.

Sorry posted without finishing.
I tell the guy oh will their was a whole unit put in the truck last week as tells me the part will be cover and they can install it for 750 now. So I say I'll be over to pick the truck up and they ordered me a new unit for the truck. So I guess I'll be taking the truck apart once again becauce of a defective part from GM, SWEET!!!
So I hope that it really was a defective part and once i get it tomorrow and put the truck back together this will be the end of this problem. I'll update after the reinstall with the results.
Paul

I also wanted to ask what should the fuel pressure be at, the dealer so it drops to almost zero once its turned off.
I was getting a steady 48-49 on my gauge i'm guessing that its to low to start the truck. Read that it shold 50-60psi 55psi being ideal but I also read 60-66psi anyone know what it should be?

my book has 60 -66psi for the V6 and the small block V8,56-62 for the 7.4L


Sean

97 4x4 burb