# 1997 Subaru Fuel delivery issue



## 97LegacyOutback (Jul 21, 2012)

Ok, so I have a 97 Subaru Legacy Outback with the 2.5. My wife drove it up to the gas station the other day, and when she cam out it wouldn't start. I brought it home and started testing. Just replaced the fuel pump relay today with no effect. So here's what I have:

- Battery voltage at the red wire on the relay connector at all times
- Battery voltage at the yellow wire with the key on
- Continuity to ground at the black wire below the blue-yellow wire on fuel pump connector
- Continuity between the black-red wire on the relay connector and the blue-yellow wire on the pump connector, however with the relay installed, I can't get a voltage reading from the blue-yellow wire with the key on or while cranking
- Pulled the pump, supplied power and ground and it started instantly
- Pulled plug wire off the coil and cranked engine, has spark
- I did not test anything on the purple wire at the relay connector since it runs directly to the ECU...

With everything hooked up I can turn the key on, crank the engine, but the pump never turns on... 

Hoping someone on here might have some sage advice for me. I really need to fix my car before Tuesday so I don't get dropped from my classes.


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## octaneman (May 13, 2009)

Hi 97LegacyOutlook


Swap fuel pump relay with a known good one. 

Does the enging fire ?


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## 97LegacyOutback (Jul 21, 2012)

Swapped a good relay. Engine turns over and I have spark, but still no fuel. I just ran a jumper wire today to provide direct power to the pump and it turned on instantly. The car starts and runs, at least in idle, this way. I checked for a short between the relay connector and the pump connector, nothing. I'm starting to think it might be the ECU circuit that's connected to the purple wire on the pump relay. Is there any way to test this theory without frying my ECU?


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## octaneman (May 13, 2009)

97LegacyOutback said:


> Swapped a good relay. Engine turns over and I have spark, but still no fuel. I just ran a jumper wire today to provide direct power to the pump and it turned on instantly. The car starts and runs, at least in idle, this way. I checked for a short between the relay connector and the pump connector, nothing. I'm starting to think it might be the ECU circuit that's connected to the purple wire on the pump relay. Is there any way to test this theory without frying my ECU?





There is , by checking the main output +5v reference voltage from your computer, but you will need a wiring schematic of your computer's pin outs to do the tests.


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## 97LegacyOutback (Jul 21, 2012)

Did some more testing: traced the purple wire from the relay to the ecu connector. Continuity between the relay connector and ecu connector, no short to ground on the purple wire. When I check voltage with the key off, it registers very low, key on gives me battery voltage. Shouldn't this be the other way around? Doesn't the relay need a terminal on the control side to ground as well as one on the switch side?


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## octaneman (May 13, 2009)

The control side of the relay could be ground switched through the PCM, with KOEO there should be 12v to the coil side of the relay and the trigger side. The computer will activate the pump for 3 seconds until line is pressurized and then shut off the relay. You will need to check the reference voltages from the computer to the ALDL. 

From your tests so far the computer is not giving the three second delay to prime the pump. 

The problem could be from: 

1) Connection from ALDL connector( diagnostic connector) to the computer is cut. 

2) No ground to the computer.

3) Fuel circuit within the computer is shorted. 


Question: 

Does the check engine light turn on/off when you cycle the key to the on position ?


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## 97LegacyOutback (Jul 21, 2012)

If you mean key on, yes. It lights up and stays on. If I turn the key to crank, all the lights shut off as usual until I release the key. Checked for DTCs with an OBDII scanner, nothing there. 

I also checked the connector under the rear set for the fuel pump, everything there checked out fine as well, continuity and short wise. Still no voltage from the relay. 

By ALDL do you mean the OBDII connector, or is there another I should be looking for?


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## octaneman (May 13, 2009)

97LegacyOutback said:


> By ALDL do you mean the OBDII connector, or is there another I should be looking for?


Yes. 



97LegacyOutback said:


> also checked the connector under the rear set for the fuel pump, everything there checked out fine as well, continuity and short wise. Still no voltage from the relay.




Hook up a fuel pressure tester to the fuel line, then set the relay up like in the pics then place it back in the fuse holder. Take a jumper an manually ground the trigger side of the relay, maximum fuel pressure should be 36 psi. Does the fuel pump come on ? 


Here's the wiring diagram the relay ground switched through the PCM you may have no choice but to replace the PCM.


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## 97LegacyOutback (Jul 21, 2012)

That's what I was afraid of. I

've got the car rigged right now with a jumper from the fuse box to the connector under the rear seat. Pump starts when I turn the key and shuts off when I turn it off. Enough to get me to school hopefully until I can replace the ECU


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