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NuclearBacon

Fuel Pump Madness! 2001 Legacy H6 Outback

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Got an email from my dad abotu a neigbors subaru outback wagon:

 

The neighbor up the street has a 2001 Subaru Outback 6 cylinder automatic. It wouldn't start this morning. Ran fine last night. About 2 years ago, he had the fuel pump replaced (same symptoms). Almost 12 months to the day after the initial replacement of the pump (about 1 year ago), the car did the same thing it did this morning. He had it towed to the local mechanic, thinking the fuel pump went out again. Once at the mechanic, it started so the mechanic said he couldn't touble shoot if there was nothing wrong. It ran fine for the next year.

 

Now a year later (this morning), the same thing has happened. No start. Engine cranks fine. No life. OK, here is what I know:

 

Opening the fuel filler cap and listening for the pump, I hear nothing when the key is turned from off to on.

 

Disconnecting the fuel line from the tank at the fuel filter and turning on the key gives you no gas.

 

The fuel pump fuse is good. I could not locate a relay although I'm sure there is one.

 

I don't think the relay is the problem for the following reason:

I disconnected the electrical connector to the fuel pump (under the right side rear passenger seat). It has 6 female connectors. When you turn on the key, position #1 has 12 volts for about 1 1/2 seconds, then goes off. The next four pins have no power on key on. The 6th pin shows a constant 5 volts and remains on as long as the key is on. When you move the key to start, the first pin shows constant 12 volts (stays at 12 volts as long as the engine is cranking), the rest of the pins do the same as above including the 5 volt pin. I believe the power flow is correct. Should more than one of the six pins show 12 volts? What is the 5 volt pin (computer signal?) Does that power flow sound correct?

 

It appears to be the fuel pump or the in-tank electrical connection to the tank. Is there any way to confirm the pump is bad, short of buying a fuel pump and crossing your fingers? Where is the best place to buy one? I tried 1st subaru parts dot com however they have the whole assembly for about $273. Other sites show a pump only for as little as $55. I did find a pump only, brand Airtex, for $130. Is that a good brand? Is there a common problem with the outbacks and their fuel pumps or the in-tank electrical connections? Due to factory problems, is it best to buy the whole assembly instead of just the pump inself? Could you put this problem on your Subaru site and ask the experts?

 

Is the fuel pump bad again? Are there aftermarket brands to stay away from? Is ther some way to confirm the pump is faulty? Has someone out there bought an "inexpensive" pump and had good luck with it? And, lastly, although it looks like it is a very simple job, is there something I should look out for during the removal and replacement?

 

Any help would be great!!! thanks everyone!!!

Luigi

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There should be a test lead for the fuel pump somewhere under the hood. If not pull the rear seat up and splice a 12v line straight from the battery into the power wire for the pump and see if it starts working. (be sure to put a fuse on the wire in case you drop it and it hits metal)

 

There should be a relay for the pump in the main relay/fuse box under the hood. The owners manual should tell you which one is which. Try swapping it with another relay and see if that works.

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The presence of voltage going to the fuel pump when the connector is not under load doesn't mean too much. (You said you disconnected the connector going to the fuel pump.) If there's a corroded or high resistance connection upstream of your voltage test point, you can measure +12v ...which would drop to next to nothing when faced with the low resistance of a fuel pump which can draw 10 Amps!

 

Can you back-probe the connector WHILE it is connected to the fuel pump? That's a much more valid test.

 

Also, I don't know if this particular pump is grounded through the tank or externally, but you also need to verify that the ground pin of the pump is at ground voltage- i.e. there should not be any reading on your meter if you measure between the ground on the pump and the chassis of the car.

 

There are plenty of 10+ year old, 200K mile Subarus out there with their original fuel pumps, so the failure of two seems a bit fishy. I wonder if there's a bad connector which was "fixed" by unplugging and reseating during the first replacement of the pump. Then again, perhaps the first failure was a fluke and the replacement pump was substandard- you could be right.

 

Fairtax's idea is a good simple way of isolating the problem too.

 

good luck,

 

Nathan

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replace it with new or used.

 

maybe it was replaced the first time with aftermarket or something cheap.

 

Subaru ones rarely fail, just get a new or used one. should be very cheap as there is zero demand for them.

 

i wouldn't mess with those aftermarkets/kits or non-OEM style as you'll likely have to do some wiring. a fuel is just a pump so in some ways you can install dozens and dozens of different pumps in that OBW - probably fuel pumps from an Army tank if you wanted to resize the lines and wire it up. the wiring can be annoying though and who wants to go cutting connectors on a 2001 OBW?

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The fuel pump is turned on briefly when you first turn the key to ON. So pin #1 that had the voltage on it for about 2 seconds is the correct pin for power to the pump I believe. As was correctly stated by Hankosolder2, checking the voltage while the circuit is broken may not tell you what you need to know about the trouble. If there still is voltage on that lead when it is connected to the pump motor then the trouble is most likely with the controlled ground for the pump through the ECU. But if the supply voltage goes low when reconnected to the motor then the fuel pump relay is most likely at fault. Since this is an intermittent problem I would suspect the relay is at fault here. When the ECU connection fails it is a hard failure due to a solid state component failure inside the ECU.

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One of the members here sent me some info on the wiring so I can be more detailed here.

 

The power to the pump motor is on a red/black wire and is really pin 2 of the connector that ties to the pump. The even number pins are on that row of pins and the odd numbered ones are on the other row of 3. The ground side of the pump is a black/white wire on pin 1.

Edited by Cougar

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FAULTY PLUG at the top of the fuel pump!!!! traced it and traced it... then a wiggle :)

 

All is well and his H6 is back on the road. thank you to ALL!!!!

Luigi

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