98 Outback 2.5 - erratic fuel pressure - Subaru Outback - Subaru Outback Forums

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Old 06-12-2010, 03:08 PM   #1 (permalink)
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Default 98 Outback 2.5 - erratic fuel pressure

I have a 98 Outback with a 2.5L, automatic trans. I am getting good fuel pressure on my pressure gauge when the key is turned on, but once the car is started (hard to get started and won't run above 1200 RPM), the pressure reading drops to zero, but once the engine stops, the pressure goes back up and holds for quite a while with the fuel pump off.
I have looked at the fuel pressure regulator and don't see any signs of fuel at the vacuum line and the vacuum seems to work OK and holds pressure. I have checked the fuel filter and it is clear.
I am looking for ideas on what to check next. In an effort not to leave anything out; I have to give a little background on what happened recently, my kid was driving the car, slid on wet pavement and hit a curb with the passenger side rear wheel and the car flipped on the passenger side (very little cosmetic damage). He called his friends, they came in about ten minutes and flipped the car back on its wheels, they then changed the rear tire (broken wheel) and started it up and drove it to his friends house a couple of blocks away. The car ran fine. I had the car flat bedded to my house a bit later, the tow truck driver started the car, repositioned it and then delivered it to my house. When we took it off the truck (driveway has a pretty steep slope), the engine was pointing downhill. When I tried to start the engine to put the car in the garage, this is when the problem started and I couldn't get it above 1200 RPM without it dying, by the way, it won't idle either.
Sounds like a pressure regulator, but I don't have a lot of money to throw around right now (out of work) and don't want to replace unnecessary parts. Any feedback you can give on what else to look for will be greatly appreciated.
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Old 06-12-2010, 09:19 PM   #2 (permalink)
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For starters, I presume you're checking the fuel pressure at the engine. A drop in pressure at the engine could be due to a restriction in the fuel line from the pump to the engine or at the pump itself (in the tank).

How did you check the fuel filter?

The pickup screen on the pump might have become blocked by dirt in the fuel tank that was disturbed when the car tipped. This, as well as a partial blockage in the line would be consistent with the pump being able to restore and maintain pressure when the engine isn't consuming fuel but not maintain enough fuel delivery when the engine is running.
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Old 06-13-2010, 10:55 AM   #3 (permalink)
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i had the same thing happen to me with a forester. i could never figure out what was wrong with it. i ended up junking it cuz i spent alot of money trying to get it running and couldnt. i hope you find out whats wrong it will probally be the one thing i didnt think of. i change the fuel pump,sending unit,fuelfilter,pressure regulator,injectors,crank sensor. the only thing i was thinking after i junked it was maybe it had a fuel pump shut off saftey device. well goodluck
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Old 06-13-2010, 09:35 PM   #4 (permalink)
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There actualy is a valve to stop fuel flow when the car is flipped (roll over valve). It may have issues as I dont know if it is a one time use valve.

Have you actually done a real fuel pressure regulator test.

plug into the fuel line with a T after relieving pressure.
Start car and and let it idle. Take pressure reading and compare to spec.
Detach vac hose to fuel pressure regulator and watch the pressure gauge.
Pressure should go much higher then the previous one.


Get the haynes manual as I am not typing everything in here but it sounds like a bad fuel pressure regulator.

The lower the vac the higher the pressure, the higher the vac the lower the pressure.

Rolled the car with just "minor" damage?
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