Fuel Pressure Problem

edfiero1

Member
Apr 6, 2017
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Any ideas on this crazy problem??

Start up the car cold, Fuel pressure is 40 with Vacuum line disconnected from the FPR.

Drive for 5 minutes, and car runs normally. After more than 10 minutes, the fuel pressure goes DOWN every time you give it throttle to the point it almost dies.

Pinch off the return line and the pressure does NOT go up.

Shut the car off for 10 minutes, start up again, all seems normal, then after about 5 mins start loosing fuel pressure again. This can be repeated at will.

Where is the problem that it only shows up after 5 to 10 minutes???

Thinking this was obviously a problem of when the pump gets hot, I used the underhood 'hot wire' to run the fuel pump while the car was OFF in the garage. Ran the pump for 30 minutes. Started the car, and it still ran fine and had good pressure for 5 minutes before it started acting up.
 

ScottHeidinger

Active Member
May 2, 2015
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northeast Florida
Sounds fuel pump related to me. Check wiring as well but if you pinch the return line and fuel pressure doesn’t rise I would start by looking at the pump. How old is the pump? Has the fuel filter been changed? Stock fuel pump hangers can also have electrical issues where the wires go thru the tank or could be a ground wire issue at the tank. I would start there.


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getdowngranny

Mr. Fix It
Jan 8, 2006
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Check voltage at the pump while you have the low pressure problem.... If voltage at pump checks good, change the pump.

Before changing anything just check all your connections and make sure everything has good continuity.
 
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Turbo6inKY

Short Guy
Jun 18, 2001
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Check voltage at the pump while you have the low pressure problem.... If voltage at pump checks good, change the pump.

Before changing anything just check all your connections and make sure everything has good continuity.
This guy right here.

The fuel system isn't terribly complex. If pressure below where it needs to be, it has to be the pump or the filter. If the filter's not clogged, then you move backwards to the pump. Either the pump isn't getting enough juice because of bad wiring or it's going bad.

If pressures are to high, you have a line restriction.
 

edfiero1

Member
Apr 6, 2017
101
3
18
52
No, still an open issue. Haven't gotten back to it. Too cold to drop the tank down so I can get to it.
I have the same problem using factory wiring and 'hot wire' which is a big 12 gauge wire running back to the trunk. Wiring from trunk to pump looks new, but haven't dropped the tank to actually check the voltage at the pump.
 
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