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roybelding
roybelding, Master Tech/Trainer
Category: GMC
Satisfied Customers: 4820
Experience:  35 years of retail operations on all vehicles
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I've got a 95 GMC Yukon with the 5.7 L motor. One day the

Customer Question

Hello. I've got a 95 GMC Yukon with the 5.7 L motor. One day the truck would all of a sudden not start. Then the next day it started. But noticed it ran a little ruff. So trying to diagnose it I was checking the fuel pump first. I turned the key to on and heard the injectors buzzing like it was running 100 miles an hour. Shut the key off and decided it was the computer. Changed the computer and everything seemed fine. Now it's doing it again. What else could cause this problem ?
Submitted: 2 months ago.
Category: GMC
Expert:  roybelding replied 2 months ago.

hello, my name is ***** ***** I will be glad to assist you. please allow me a couple of minutes to gather some basic info.

Roy

Customer: replied 2 months ago.
Thanks.
Expert:  roybelding replied 2 months ago.

your welcome.

first, I would check the actual fuel pressure. just because it is running does not mean it is providing the needed pressure.

if you dont have a tester, you can rent one at a parts store to check.

was the check engine light on??? did it have any stored codes???

Roy

Customer: replied 2 months ago.
No codes at all. Fuel pressure was good. With the key on and not running the injectors were pumping in fuel. When it does that it won't start cause it's flooded.
Expert:  roybelding replied 2 months ago.

what is the fuel pressure???

Customer: replied 2 months ago.
54 psi running.
Expert:  roybelding replied 2 months ago.

ok,

can you verify the year please??? 95 is a low pressure unit of 9-13 lbs.

Customer: replied 2 months ago.
Ok. Sorry. I didn't check it myself. I'm going to look at it tonight. Somebody looked at it and said the fuel pump is good. Something is causing the injectors to run without the engine turning over at all.
Expert:  roybelding replied 2 months ago.

lets get the correct vehicle and correct pressure before we go after that

Roy

Customer: replied 2 months ago.
Ok. The vehicle is correct. I'll get back to you tonight.
Expert:  roybelding replied 2 months ago.

ok

Expert:  roybelding replied 2 months ago.

how are you making out???

Customer: replied 2 months ago.
Not good. You can't check the pressure on this motor. Back to the computer though. When I turn the ignition to on the check engine comes on for a second goes off for a sec then comes back on. That doesn't seem normal to me.
Expert:  roybelding replied 2 months ago.

who came up with 54???

sure you can. you need to break in at the filter and use a T fitting. do it all the time

Roy

Customer: replied 2 months ago.
Ok. I have to look for that fitting. I have a fuel gauge with a schrader valve fitting. The mechanic that looked at it said the fuel pump and regulator were good. Maybe he said 14 psi.
Expert:  roybelding replied 2 months ago.

I would want confirmation on that. the first guess was out of wack.

Roy

Customer: replied 2 months ago.
Ok. I got ahold of him. He said it was 14 psi.
Expert:  roybelding replied 2 months ago.

to be honest, I do not trust him.

he lied to you once.

did you get the adapter??? I would verify yourself.

Roy

Expert:  roybelding replied 2 months ago.

please dont forget to rate me as it is the only way I get paid for my efforts

Roy

Customer: replied 2 months ago.
Ok I got the pressure tested. It's about 15 psi.
Expert:  roybelding replied 2 months ago.

engine running???

Customer: replied 2 months ago.
That's engine off. Engine running is about the same. Around 13 14.
Expert:  roybelding replied 2 months ago.

ok, I see you are working with another tech as well and you accepted his answers. you should stick with him.

Roy