# 1997 5.7L Fuel Pressure ?



## scottL (Dec 7, 2002)

1997 Chevy K3500 5.7L. What should the fuel pressure be? When I ran a test with a presure guage it topped around 60-62. A few seconds later the pump shut off after making pressure and the guage dropped to 20 psi and held steady. Does this sound right?

THANKS!


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## wagonman76 (Jan 31, 2005)

Does it run like that?

A coworker of mine has one and he always told me it needed pressure in the low 60s, maybe even 65, to open the injectors. If it is running like that, then Id think theres a leaking injector relieving the pressure.

If someone else cant help you first, Ill ask him when I go back to work Monday. Hes an ex-GM mechanic, he just got tired of making his living that way.


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## scottL (Dec 7, 2002)

I wasn't able to do an engine running test. 

Honetly the truck seems to run fine but, I keep getting Bank 1 too lean 171 error. I've got a new fuel regulator, two new o2 sensors on bank 1, the fuel pump is 4 years old and I had the new style injectors put in 2 years ago. I was fisihing on the fuel pump as the dealer made a comment the year after they did it claiming it might be a tad weak. Always stuck in my mind so, I tested the pressure. THe only fact I could find was the high range was correct but, the low range ... not sure.


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## NJBuickRacer (Jan 20, 2005)

If you're getting a lean code on 1 bank, check the oxygen sensor on that bank for contamination and for vacuum leaks that could potentially feed any/all cylinders on that bank unmetered air. PCV valve having the wrong flow rate could potentially trigger that code as well.


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## scottL (Dec 7, 2002)

Thought I would update ...

I ended up taking it into the dealer. When they ran the fuel pressure test it dropped as such. It turns out the fuel pump went bad again. It should have reached around 60-62psi when the pump turns off/reaches pressure then only drop a few pounds.

Now I'm getting an error of lean on both banks, intermittently. The dealership is thinking it is the mass air flow sensor. I had repleaced the MAF 6 months ago with an aftermarket that was suppose to be very highly rated - granatellimotorsports.com. I called them yesterday and explained the problem ... Turns out in cold weather (sub 40 degrees ) their units allow more air flow and the computer believes the system is then lean beyond it's ability to compensate.


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## NJBuickRacer (Jan 20, 2005)

Granatelli MAFs are junk, I have a couple here I use as doorstops and paperweights. Because of the way they meter air, it also reduces line pressure for your trans since the PCM calcs line pressure against MAF values.


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## scottL (Dec 7, 2002)

I had to update..... I ended up working with the dealer, then contacting granatellimotorsports.com tech support a few times. It turns out in cold weather and/or with winter fuel they can cause the lean fuel condition on both banks. I found this to be true sub-40 degrees. Makes the truck less driveable too.

I swapped it out for a napa remanufactored with warranty and sent my granatelli MAF back to summit racing. ( Summit racing was very good to deal with ! )


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