Stock Fuel Pressure Question

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Stock Fuel Pressure Question

Postby killian96ss » Sun Apr 23, 2006 11:04 am

The S10 repair manual that I have says that the fuel pressure should be 60-66 psi with the key on and engine off. When I turn the key on my fuel pressure hits 62 psi, but then it drops to 40 psi in 3 seconds and 20 psi by 9 seconds. I know the fuel pump turns off after 2 seconds, but my manual says that the fuel pressure should not drop more than 5 psi after 1 minute. With the engine running my fuel pressure is 52 psi (park or drive) and when I quickly hit the gas it will shoot to 61 psi and then rapidly fall back to 52 psi. I wonder if I have a leaking injector causing the fast bleed off? :? The reason I suspect a leaking injector is because occasionally my truck will crank without starting for about 3-4 seconds. The fuel pump seems to be working fine, but something seems wrong. :? Any ideas? :?:

Steve
Last edited by killian96ss on Fri Sep 15, 2006 9:02 am, edited 1 time in total.
2005 ZR2 Blazer / Mods- Spectre CAI, Descreened MAF, Shaved Throttle Blade, 31" Goodyear Kevlar MT/R's, Black Rock Rims, MSD Street Fire CDI & Super Conductor Wires, Accel Cap, Rotor & Coil, Flowmaster 30 Series, Gibson Tailpipe, ES Bushings, Goodridge Brake Lines, Power Slot Rotors - 1996 Impala SS / Mods- Too Many To List - 1988 S10 Blazer / Mods- Too Many To List - 2001 S10 Crew Cab 4x4 / Mods- Too Many To List *Wrecked 12/06*
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Postby HenryJ » Sun Apr 23, 2006 12:16 pm

I would still suspect the fuel pump. The foot valve in the pump may be leaking. I have replace half a dozen for that reason.
Try free flowing the pressure relief on the gauge at idle and see if it maintains an adequite fuel pressure. Not that that will tell much , but I always check.

The cranking 3-4 seconds is the "tell" for me.
Try this after it sits overnight. Turn the key on 5 seconds then off two seconds then on , pause for one second and start. If it starts easier the pump is your problem.

The leaking injector will usually show up by an increase in oil level and perhaps a misfire code thrown.

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Postby killian96ss » Sun Apr 23, 2006 12:55 pm

With the key on and engine off should my fuel pressure hold steady for a few minutes or is it normal for it to drop to 20 psi within 9 seconds. If my pressure drop sounds like a problem then I will use my warranty and let GM fix it, but I have to make sure there is a problem since I will have to pay a $100 deductable no matter what they do or don't find. :roll:

Steve
2005 ZR2 Blazer / Mods- Spectre CAI, Descreened MAF, Shaved Throttle Blade, 31" Goodyear Kevlar MT/R's, Black Rock Rims, MSD Street Fire CDI & Super Conductor Wires, Accel Cap, Rotor & Coil, Flowmaster 30 Series, Gibson Tailpipe, ES Bushings, Goodridge Brake Lines, Power Slot Rotors - 1996 Impala SS / Mods- Too Many To List - 1988 S10 Blazer / Mods- Too Many To List - 2001 S10 Crew Cab 4x4 / Mods- Too Many To List *Wrecked 12/06*
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Postby HenryJ » Sun Apr 23, 2006 1:47 pm

You are right it should not drop. Bleed the air out of the gauge and turn the key on to get the highest reading possible. It may take several times. The pressure should not drop more than 5 psi in 1 minute. Then bleed down to 10 psi and watch the pressure for 5 minutes. It should drop no more than 2 psi.
Sorry I got ahead of myself. It sure sounds like you do indeed have a problem and warranty should take care of it. I would guess that a power flush will be in order. Take along the last fuel filter receipt so they don't blame a lack of proper maintainance.
You might even try running some fuel system cleaner through yourself. I try to run a bottle trough every other oil change.
If you have warranty, I'd let them figure it out. A new fuel pump would be a good start.
You're in California, so you might end up with updated injectors? Who knows?

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Re: Stock Fuel Pressure Question

Postby RichSellers » Wed May 29, 2013 6:00 pm

My truck would not start a few days ago. Had it towed to my house. I suspected a problem with fuel pump/filter/whatever. During the previous few days (maybe a week), I've noticed an intermittant hesitation when accellerating.

I rented a fuel pressure tester and it read about 61-62 psi with keys on but engine off. Turned off key and the pressure held - maybe dropping 1-2psi after a minute or so.

To my surprise, the engine started, but the pressure falls to 52-54 psi when the engine is running and stays there pretty steadily.

Should I replace the pump?
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Re: Stock Fuel Pressure Question

Postby HenryJ » Wed May 29, 2013 6:33 pm

When was the fuel filter last replaced? Did you do ALL these tests: Fuel system diagnosis

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