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Fuel delivery issue electrical


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11 replies to this topic

#1 McKrunk

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Posted 28 August 2012 - 11:28 PM

1998 Legacy Wagon L 2.2 Fuel pump or related electrical problem.
note: NOT a clog in the fuel lines or filters already ruled that out.

Pulled the pump out and bench tested it: okay it works.
Replaced the fuel pump relay: IT WORKED (engine ran) FOR 5 MINUTES, then stopped.
Replaced pump relay a second time: nothing.
Jumped pin 2-4 at the relay socket (to bypass the relay): no change.
Measured 12 volts at the connector to fuel pump (at fuel pump end, in bypass mode)

I'm thinking it may be:
A bad ground somewhere in the circuit?
A short in the wire between the connector and the pump itself?
(but why did it work when I replaced the relay the first time?)
Here is a clue, when I replaced the pump replay the first time, then it stopped, I felt the relay itself and it felt really warm. Maybe that's normal...
Okay, what am I missing or overlooked here?

#2 Fairtax4me

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Posted 28 August 2012 - 11:42 PM

Either the relay went bad, and then the pump did, or the pump is just bad.
Not uncommon for a pump to be intermittent when it fails.

2 larger (somewhat) wires at the pump. One is 12V (possibly Brown, possibly Black/Red). The other should be Black, is chassis ground. Could just be a loose connection. The fuel pump wires come into the car somewhere under the back seat IIRC, and there is/might be a connector there.

#3 gregB

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Posted 29 August 2012 - 12:13 PM

On the sedans it is two bolts and a catch to remove back seat bottom.

Then you have access to the two wire voltage connector to the pump.

If you connect 12v to the pump side, with a hose pulled off the fuel filter you can check pump for performance, installed in the tank.

Learned all this last week on my fuel filler pipe project. My pump was drawing 4 amps as it was pumping fuel.

#4 Cougar

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Posted 30 August 2012 - 01:53 PM

When the relay contacts build up a resistance heat is generated when the load is drawing current. Some heat may be normal due to the coil.

The fuel pump most likely uses a controlled return to ground that may go through the ECU. If the ignition system isn't working the ECU will shut down the pump by opening the pump circuit ground connection. Have you checked for spark to the plugs. Check all the fuses also and make sure they are ok.

#5 McKrunk

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Posted 15 September 2012 - 12:38 PM

There IS spark, air, and there are no fuel restriction issues. This is an intermittent problem. Very elusive indeed. Scan tool says it is the FUEL TEMPERATURE SENSOR. A mechanic says there is a SECONDARY FUEL PUMP. Really, where is it? A this point I'm completely baffled. Supposedly the fuel temp sensor is not a discreet replaceable part, and the ENTIRE fuel pump and fuel gauge sender unit Assembly needs to be replaced for $700+ Really?
Please any experts here want to give an opinion or bust some myths here?

#6 propane

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Posted 15 September 2012 - 03:57 PM

Might mention mileage on car. Subie fuel pumps are long lasting. Never heard of fuel temp code, The fuel tank looks like saddle bags, straddling the drive line hump.
OK a solution Agree with ? bout it prolly be the pump.(relay failure rare.)Wise to keep the tank above a third, keeps pump cooler, reduces pumping effort etc Were me, since subie F pumps are so easy to swap, I would a used one, just me. Maybe a pay to pull yard

Edited by propane, 16 September 2012 - 01:02 AM.
error,clarity


#7 Cougar

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Posted 15 September 2012 - 09:02 PM

Subie pumps do fail fairly frequently and from what you stated about the relay it makes me think the pump is bad. You could apply power directly to it and see if that makes adifference. You say the relay was real warm and if the pump shaft is stalled that would draw a lot of current and heat up the relay. Again, I think if you replace the pump you will be good to go. There isn't a secondary pump so forget about that. There are two level sensors used in the tank for the fuel gauge.

#8 Frank B

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Posted 16 September 2012 - 11:20 AM

Keep in mind that when you do a bench test, you may be using a source that is of a higher amperage and or voltage than what the part would be subjected to while in the car. Some is lost in the circuits in the car.
A bad pump can sometimes be "fixed" by running a new circuit directly from the battery because of the stronger, direct power.

I suggest getting a cheap pump on Ebay, just the pump, not the assembly. If anything, just to use to test the circuit. If it all works out, then save up or shop around for the pump that you want.
I've used those before with great success. In a Lumina I had, ans S10 that I had, and in my dads Ranger. They are all still working. The lumina was 3 years ago, the S10 2, the Ranger 1.
This is one from the same seller that I bought mine,
http://www.ebay.com/...=item5890402e4c

#9 McKrunk

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Posted 20 September 2012 - 10:28 PM

Replaced the entire pump and sender unit assembly from a known working exact swap part. Still not working. Replaced with another new relay. Still no work. This leads me to believe something with the ECU? There IS spark, so maybe something else with other electrical sensors? I did a scan and no codes came up either. I'm still baffled.

#10 Cougar

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Posted 21 September 2012 - 02:50 AM

The info I have for a 97 Legacy shows there isn't a fuel pump controller for the pump. One of the wires going to the pump is black and it ties to chassis ground. You stated earlier that there was 12 volts getting to the pump. Check the black wire and see if you have 12 volts there also. If you do that means the ground connection to the pump is open.

#11 ivans imports

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Posted 21 September 2012 - 09:52 AM

comutator bars on pump worn down to far and pump drawing to many amps over loads the circut it grounds with the engine harness grounds on engine doubt thats the problem bad pump or realy power feed problem or pinched wires somwere

#12 ivans imports

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Posted 21 September 2012 - 09:58 AM

feul temp senser will not do thiss could set code but pump will still work. Just one realy is controled by main realy and ecu the main has to power up before the feul pump realy can turn on




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