Fuel pressure bleeding down
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Elder User
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From: Indiana
Fuel pressure bleeding down
My son has a Ford car that was hard to start. We check the fuel pressure at the schrader valve and when the the key is initially turn to the on position it had no fuel pressure (pump only ran for a couple of seconds). Turn the key off and back on 2 or 3 more times and then the fuel pressure got to between 25 to 30 psi and the car would start right up. With the car running the fuel pressure was about 32 psi and with the vacuum hose disconnected to the fuel pressure regualtor it would go up to 40 psi. Everything seem to be working okay once the car was running.
What part of the fuel system would allow the fuel pressure to bleed down when the car is not running? How do I check to see if the fuel pump or pressure regulator is going bad? Any input is appreciated.
What part of the fuel system would allow the fuel pressure to bleed down when the car is not running? How do I check to see if the fuel pump or pressure regulator is going bad? Any input is appreciated.
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Joined: Apr 2004
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From: maui.HI
I'm not sure about the intank style fuel pump on most EFI cars, but the external hi-pressure pump found on most trucks have a small check valve built into the pump to keep some residual fuel between pump and fuel rail while engine is off. If that stays open, you wont have the build up pressure at start up. I believe your engine run fuel pressure sounds a little low. I can look it up if you can tell us what Year, Model, and engine size you are working on.
Last edited by mauicruza; Jan 14, 2006 at 01:52 AM.
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From: Indiana
It is a late 90's ford taurus. I don't remeber off hand what size motor it is. I do remeber that my son said there were 4 different variations of this size motor. He had a manual for the car and the fuel pressure was within specs. which was if I remeber was 32 psi with vacuum and about 40 psi with out vacuum. I believe your right on the check valve. I have replaced a few of them myself over the years and it seems like there is always a check valve on the pressure side of the pump.
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