GM Truck Club Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
I need help trying to figure out what is going on with my burb.

It was having some serious hard starting issues and now nothing. I changed the fuel pump, and fuel filter. I can hear the pump prime when I turn the key. If I remove the cap(like a valve stem cap) and depress the check valve gas will shoot from there. I also changed the MAF sensor. I pulled a few plugs and they are all in perfect condition. No oil leaks, 122K miles. 5.7 Liter V8.

I am going to try some starting fluid to see if the vehicle starts with a little help, but I get nothing. The burb cranks over and stumbles a bit, but won't start.

Thank You,

Big D
 

·
Registered
Joined
·
2,428 Posts
See my post here, or search the forums. This is a pretty common problem and with some ordinary troubleshooting you should be able to diagnose it for the correct fix. Post what you find to help the next guy.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #3
I just finished pulling the ICM and took it up the street to have it test. Passed. While I was there I grabbed a can of starting fluid. A 2 second blast down the TB and the Burb starts and runs until the starting fluid is used up, about 10 seconds. apparently fuel isn't getting into the TB.

Like I said before, I changed the fuel pump yesterday evening, and the fuel filter this morning. If I depress the check valve right before the TB, gas shoots out.

What the heck is going on.

Big D
 

·
Registered
Joined
·
6 Posts
Discussion Starter #4
I've also use a code scanner and it came up clean with out any codes.

I am leaning towards the Fuel Pressure regulator, but from what I have read, and the fact that I only have about an hour before the sun goes down, I won't have time to tackle. I guess I will have to farm it out.
 

·
Super Moderator
Joined
·
3,377 Posts
have someone try to crank it while you watch the throttle body looking for the sprays of fuel into the carb. There may be something wrong with the fuel injectors, mechanically or physically.
 

·
Premium Member
Joined
·
1,625 Posts
You can check the injectors old school with a 12 volt test light. Just put the light on the injectors electrical leads. You should get a pulsing light. If not it’s electrical. If you do get the test light to flash then it’s a clogged or defective injector.

Or fuel pressure regulator.
 

·
Moderator
Joined
·
1,536 Posts
Have you put a fuel pressure gauge on it? These Vortec engines require 50+ (spec is 60) psi to start. 40 psi would "shoot" like a lot of pressure, but wouldn't be enough to start.

It seems that a lot of the time, if there's adequate pressure, the problem turns out to be the poppet valves themselves. GM has had some issues with them, and has even issued an updated spider with better injectors.
 

·
Registered
Joined
·
1 Posts
I just got my 97 Sub with the 7.4 liter back out of the shop. Same thing with the hard starting and very rough idle. The new fuel pump and filter several months back did not cure the problem. The Fuel Pressure Regulator was the culprit. It went bad and was leaking raw fuel which caused the hard starting and rough idle. It was about $550 to repair at a shop. Hope that helps.
 
1 - 8 of 8 Posts
Top