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2001 jimmy 4.3L fuel pressure problem.


2001jimmy
05-14-2011, 11:30 AM
For the last few months my gas milage has got down to about 8 mpg.

Decided to check fuel pressure today. Hooked the gauge up to the Shrader valve turned key to on, Pressure went to 60 psi and within 30 seconds was down to 50psi. Within the next minute was down to 40. Am I looking at a bad regulator?, anything else to look for?

Thanks!

4x4 blazerguy
05-14-2011, 01:41 PM
I would say your looking at a leak. Possible injector, the spiders are know to leak.
Check your fittings external. But they should hold pressure & the drop of that much means you are leaking fuel. That would explain the poor mileage.

MT-2500
05-15-2011, 05:20 AM
For the last few months my gas milage has got down to about 8 mpg.

Decided to check fuel pressure today. Hooked the gauge up to the Shader valve turned key to on, Pressure went to 60 psi and within 30 seconds was down to 50psi. Within the next minute was down to 40. Am I looking at a bad regulator?, anything else to look for?

Thanks!
Specs are 60/66 lbs.
You should see 65-66 lbs regulated pressure key on pump on prime up.

To find leak down block off return line and check for 95-105 lbs full pressure from fuel pump.
If not your fuel pump is weak.
Then watch leak down.
If you still have a fast leak down then prime up pressure and block off in line between pump and fuel gauge fitting.
The fuel pump has a check valve and inside pressure plastic line that should hold pressure pump off.

If pressure is still leaking off with return line and in line blocked off them check fuel lines and filter for leakage.

If no leak there then pull upper platinum and check regulator and fuel injector body and injector poppet's for leakage.
There has been some post with injector body cracked or injector seals leaking.
Also regulator have been known to leak external.
Prime up pressure with cover off and look for any leakage.
Where there is a leak there is usually a bright clean spot.

A pressure leak down may not be all of your low gas mileage problems.
Low fuel pressure or engine/computer sensors or just needing a good Ac- delco tune up may be your problem.
How many miles on your last know good tune up?
Any check engine lights or flashing light?
Any engine miss

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