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Gary
Gary, GMC Technician
Category: GM
Satisfied Customers: 15914
Experience:  15 years gm master tech/15 years ASE master tech
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Just rebuilt 1998 7.4 vortec. Only has 45lbs of fuel

Customer Question

Just rebuilt 1998 7.4 vortec. Only has 45lbs of fuel pressure. I have replaced fuel pump once and fuel FPR TWICE. Clamped of return line and got 80 psi. I do not see any external leaks.
JA: How many miles are on the vehicle? And when was it last serviced?
Customer: 153,000 and serviced three days ago. I also have change fuel filter
JA: Are you fixing your 80 yourself? What have you tried so far?
Customer: My 80?????
JA: Anything else you want the mechanic to know before I connect you?
Customer: No
Submitted: 3 months ago.
Category: GM
Expert:  Gary replied 3 months ago.

Welcome! My name is ***** ***** I will do my best to assist you with this problem.

Expert:  Gary replied 3 months ago.

i am sorry for the long wait

if you connect the fuel pressure gauge to the fuel line from the fuel tank where it goes into the fuel filter what is the fuel pressure ?

Customer: replied 3 months ago.
45 psi
Expert:  Gary replied 3 months ago.

if it is only 45 at that line with the gauge put in like i said the issue is in the tank of either the pump not making the PSI or it can not due to a power or ground issue

that takes the regulator out of the mix as being a problem

if you run a new temp GOOD wire from the frame to the big black wire at the fuel pump connector will the psi go up to spec ?

Customer: replied 3 months ago.
I don't think it's the pump because its new and when I crimp return line off it will go to 80psi. Unless I'm stupid and don't know anything. lol
Customer: replied 3 months ago.
Could it be fuel injectors?
Expert:  Gary replied 3 months ago.

if you disconnect the fuel line off the tank into the fuel filter and directly connect that line into the pressure gauge you are only testing the pump pressure and NOT the return system

if it reads 45 with it connected directly into the line i said it is again a pump issue or the pump can not make the pressure

Customer: replied 3 months ago.
Oh ok I see what your getting at
Expert:  Gary replied 3 months ago.

if you did connect it in to test the way i said then try a new good ground right from the frame to the big black wire at the pump connector and see if you still get 45 or not

Expert:  Gary replied 3 months ago.

how are you making out ?

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