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Fuel pump relay problems


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9 replies to this topic

#1 Mark j

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Posted 05 February 2013 - 06:56 AM

My 1997 subaru legacy outback has a problem with the fuel pump relay. After a long drive I stopped the car and tried to restart but no fuel pumping. After towing home I put in a new pump and relay. Still no pumping. If I jump either side of the controll side of the relay to ground the pump runs constant with the key on, car runs also. I can not figure out what is wrong with the controll side of the relay. Maybe a bad sensor not sending a signal to the ECU? Or just a bad ECU?

I have not pulled the codes yet I am waiting for a code reader I ordered online. CEL is off.
If the ECU is bad anyone know what units are compatable with this car? The ECU in it is this one pictured.
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#2 1 Lucky Texan

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Posted 05 February 2013 - 08:27 AM

you mean it failed to start after immediately being shut down?

And you can't hear the pump run for a few seconds when you cycle the key to ON?



is there a pressure switch somewhere that could be bad, trying to keep the pump shut off? maybe even a rodent chewed wire ?

Edited by 1 Lucky Texan, 05 February 2013 - 08:30 AM.


#3 ivans imports

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Posted 05 February 2013 - 11:08 AM

Check feul pump realy should cycle when key is turned on click on 2 seconds click off if you here thiss realy is ok if you dont hear that look at realy or realy power feed. Is very very rare to see bad ecu on those cars also make shure the warning lights and check engie lights light up when key is on thiss tells you ecu is geting power. No warning lights no power feed

#4 Cougar

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Posted 05 February 2013 - 12:30 PM

My data shows that power to the fuel pump relay coil comes from fuse 16 in the dash panel. Verify power is getting through the fuse and to pin 1 of the relay coil. You state that you can ground either side of the coil and make the pump work so I'm a little confused with that statement. One side of the relay coil has power on it from fuse 16 and grounding that side would blow the fuse. The data shows that the hot side of the coil uses a yellow wire and the ground return side is a violet wire. Pin 1 of the relay socket is the hot side of the circuit. Make sure the violet wire is making good connection to the pin of the ECU for the controlled ground connection. If that is okay then you may have to replace the ECU due to a defect in the relay control circuit.

Edited by Cougar, 05 February 2013 - 12:39 PM.


#5 Mark j

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Posted 06 February 2013 - 06:48 AM

[quote name='Cougar']My data shows that power to the fuel pump relay coil comes from fuse 16 in the dash panel. Verify power is getting through the fuse and to pin 1 of the relay coil. [quote name='Cougar']You state that you can ground either side of the coil and make the pump work so I'm a little confused with that statement. One side of the relay coil has power on it from fuse 16 and grounding that side would blow the fuse. .[/QUOTE]
Yea this is what has me confused also. I jumped it with a bent wire and I think this is where it was touching through the back of the connector. Also the pump does not run for the 3 seconds when not jumped. I will try what you suggest this weekend and see what I come up with. Could a main relay or a bad ignitor or or any othe sensors cause a relay not to work. I figure not because it does run fine with the relay jumped to ground from where I have it jumped. It is hard to see in that cramped space. Would it be easier to get to the relays through the instrument panel by removing it. Also my digram shows the violet wire going to the MPFI. I am thinking this stands for multi port fuel injection? What is the MPFI? Thanks!

Edited by Mark j, 06 February 2013 - 06:56 AM.


#6 ivans imports

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Posted 06 February 2013 - 10:49 AM

Have that exact ecu here in my hands if you need it came out of a 97 outback was hit in front but #s match 7x 22611 AD001 JA18000DJ7

#7 Cougar

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Posted 06 February 2013 - 11:49 AM

Your definition of MPFI is correct. Each cylinder has an injector for the fuel delivery. You have proved the ignition is okay since you say you can force it to run.

Since the fuel pump doesn't even turn on for a few seconds when the key is turned ON it means something is either wrong with the ECU or the pump circuit. You have proved somehow, that the pump circuit does work manually so unless a power supply line to the ECU has a problem I would think the problem is with the ECU. It is pretty easy to replace it so it might save a lot of hunting by just installing another one and see what happens.

When the engine is running, the ECU checks for ignition pulses to keep the fuel pump running. If it doesn't see any pulses it will shut the circuit down. The circuit should still work though when the key is turned ON and the engine isn't cranking, in order to prime the fuel system.

Edited by Cougar, 06 February 2013 - 11:52 AM.


#8 Mark j

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Posted 06 February 2013 - 07:29 PM

Have that exact ecu here in my hands if you need it came out of a 97 outback was hit in front but #s match 7x 22611 AD001 JA18000DJ7

What you need for your ECU? Looks like you are in Canada, does it make any difference in the software on a ECU do to any fuel differences in Canada?

#9 ivans imports

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Posted 07 February 2013 - 10:56 AM

no it shuold be the same i sell them for 100 canadian is the same # and was from a working car

#10 Jon H.

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Posted 08 June 2014 - 01:30 PM

I see the OP has only three posts he's not an active member but,  I'm having the exact same issue.  Does anybody know what the issue might have been?  

 

Jon H.


Edited by Jon H., 08 June 2014 - 01:48 PM.





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