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Author Topic: Fuel Pressure Drop  (Read 10299 times)

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Offline Scoobum

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Fuel Pressure Drop
« on: September 15 2013, 08:12:09 PM »
Got a call from a GN owner this morning. He has an in car fuel pressure gauge and it dropped to 20 lbs last nite while he was driving home with the engine under no load/boost. This morning it was back up to 38 with no load/boost. New Racetronix SS hanger and pump. AFPR is a used unit I gave him back in the spring...so it could be suspect. Also...he hasn't swapped out to a new fuel filter as of yet...and injectors are new 60's. Same thing happened to me when my AFPR went south. Open to suggestions as to what's wrong. I swear this guys car is possessed...it's been giving me fits the entire year.
 
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Offline Steve Wood

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Re: Fuel Pressure Drop
« Reply #1 on: September 15 2013, 09:26:23 PM »
or a pump that is beginning to die when it gets hot
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Re: Fuel Pressure Drop
« Reply #2 on: September 15 2013, 09:57:37 PM »
Quote from: Steve Wood on September 15 2013, 09:26:23 PM
or a pump that is beginning to die when it gets hot

Thanks Steve...hope you're wrong. That pump only has a couple passes on it and maybe a couple hundred miles of normal driving.
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Offline Steve Wood

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Re: Fuel Pressure Drop
« Reply #3 on: September 15 2013, 10:09:18 PM »
I assume the car ran like crap?  Surprised it actually kept running with pressure that low
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Offline Scoobum

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Re: Fuel Pressure Drop
« Reply #4 on: September 15 2013, 10:32:09 PM »
Quote from: Steve Wood on September 15 2013, 10:09:18 PM
I assume the car ran like crap?  Surprised it actually kept running with pressure that low
He never said. I'll take your word for it tho. His car has been down all year. It's one thing after another.
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Offline Steve Wood

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Re: Fuel Pressure Drop
« Reply #5 on: September 15 2013, 10:35:22 PM »
Ask him. If it did not, then it was not the pump or fpr
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Re: Fuel Pressure Drop
« Reply #6 on: September 15 2013, 10:44:29 PM »
Quote from: Steve Wood on September 15 2013, 10:35:22 PM
Ask him. If it did not, then it was not the pump or fpr

Will do. If it isn't the FPR or pump...what else could it be? Alternator and battery are both new.
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Re: Fuel Pressure Drop
« Reply #7 on: September 15 2013, 10:55:11 PM »
Steve...got a text back from him and he said it ran fine at 20 PSI of pressure.
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Offline Steve Wood

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Re: Fuel Pressure Drop
« Reply #8 on: September 15 2013, 11:26:51 PM »
That ain't possible so that should tell us something. bet the blms and O2 were normal
« Last Edit: September 16 2013, 12:27:26 AM by Steve Wood »
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Offline motorhead

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Re: Fuel Pressure Drop
« Reply #9 on: September 16 2013, 07:29:32 AM »
Even at 20psi the car will run fine.  The ECM will compensate and up the injector duty cycle/pulse width.
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Offline phil_long

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Re: Fuel Pressure Drop
« Reply #10 on: September 16 2013, 08:08:58 AM »
When my car idled at a of 28lbs, it wanted to die. Then I got a good gauge and realized that the gauge was WAY off.
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Offline phil_long

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Re: Fuel Pressure Drop
« Reply #11 on: September 16 2013, 08:10:11 AM »
So with the first guage I had on there, it was showing my car idling at 42 lbs or so. Then Steve sent me an Ashcroft that verified that my FP gauge was shot.
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Offline bescurred

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Re: Fuel Pressure Drop
« Reply #12 on: September 20 2013, 05:39:22 PM »
Quote from: phil_long on September 16 2013, 08:10:11 AM
So with the first guage I had on there, it was showing my car idling at 42 lbs or so. Then Steve sent me an Ashcroft that verified that my FP gauge was shot.


Which gauge did he send you?  I ordered one like a dummy that wasn't liquid filled and it is a POS... I KNOW I KNOW!!
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Offline PacecarTA

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Re: Fuel Pressure Drop
« Reply #13 on: September 20 2013, 08:31:03 PM »
Quote from: motorhead on September 16 2013, 07:29:32 AM
Even at 20psi the car will run fine.  The ECM will compensate and up the injector duty cycle/pulse width.

far as i know and  what do i know... minimum operating pressure is 26  below that iys a dribbler and at 1/2 the recommended fp the output will be so low compared to what it needs  and the ecm cant compensate that much... it will run like ass
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Offline Steve Wood

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Re: Fuel Pressure Drop
« Reply #14 on: September 20 2013, 08:45:23 PM »
The one I sent him was not liquid filled and it was not a POS.

I have seen more than one liquid filled gauge that was no good.
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