Mechanics

FUEL PUMP RELAY

1996 Subaru Outback

Engine Performance problem
1996 Subaru Outback 4 cyl All Wheel Drive Manual 175000 miles

Previously asked about a fuel pump relay replacement that resulted in the same fuel pressure problem after starting engine a couple times. I did hear the fuel pump start for a couple seconds at the turn of ignition key after installing new relay. Did not last more than 4 starts that seemed successfull, may be a flut and/or also installing new fuel filter. Now no sound from pump. I checked both, old and new relay's engage(voltage & click) for a second apon turn of ignition key.
? Is it typiical for the relay to just kick on for a second upon ignition? Or are both bad relays? Main relay?
Where should I go from here? Fuel pump. Can I test the fuel pump by hooking 12 volt directly to connector terminals and see if it kicks? Before pulling the pump out?
thanks for your guidance.
pagosajames
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Jamespagosa
May 10, 2010.



Hello jamespagosa,

When the ignition key is turned to the ON position, The PCM turn the fuel pump on briefly. For safety reasons, the PCM will turn the pump off again in a few seconds if the engine doesn't start. When the ignition key is moved to the START position and back to ON, the PCM relies on the crank position sensor signal to activate the pump.

Check for spark, compression and the crank sensor and tell me what happens
If you want to check the fuel pump, attach a digital multimeter (DMM) to the positive and negative fuel pump terminals, and then turn the ignition on. Your DMM should briefly read battery voltage (12 volts). If it doesn't, look for a break in the circuit somewhere between the fuel pump and the relay. The relay have been replaced so I assume it is good one and I believe the problem is not there.

Tiny
Mathiaso
May 11, 2010.


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