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2000 Legacy intermittent fuel cut off?


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Hey There,

One evening I went to start up my 2000 Legacy, and I had 0 fuel pressure. The relay was sending power, but I wasn't getting ny fuel. I replaced my Fuel Pump assembly with and OEM unit, and a new fuel filter.

 

2000 trouble free miles later the car begins having momentary losses of power while driving. My RPM would drop to 0, and then bounce back up. This would happen once every 50-100 miles. 

 

A week later, the losses of power got worse. The car would die, but I was able to restart it immediately. 

 

The next day, the car died and then i had to wait 5min~ for it to restart. 

 

I bought a new fuel pump relay, and it seemed like my problems were solved. 1200 trouble free miles later, the car dies and wont start for a couple minutes. made it a couple miles down the road, and it happened again. Fortunately I wasn't too far from home. 

 

I did a hard rest on the computer, went 1500 miles, and today it left me stranded when I went to drive it after work.

 

I had the car towed home, went to the garage and pulled out the multimeter to go trouble shoot it, but the darn thing fired right up! 

 

Today when I was left stranded, I noticed the fuel pump relay would click on and the immediately off. Never on long enough to send power to the pump. I'm wondering if there is a sensor that tells the ecu to cut power to the fuel pump? O'Reillys guy ran the codes but found nothing, and told me maybe my gas cap was loose...  <_<

 

 

I have driven the car on hot days, cold days, long days, etc. There doesn't seem to be any trends that correspond with driving conditions. 

 

Searched high and low but having trouble finding anything. Please help! 

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Fuel filter is brand new, also I replaced the whole fuel pump assembly, not just the pump. If it was the O-ring issue, I feel like it wouldn't perform so well 95% of the time. 

 

I am going to replace the MAP sensor, and clean out the atc valve, and see if that fixes it. 

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Could have a power issue going to the relay. If the power going in is dropping the relay can click off since the control side and load side share the same source.

 

Besides a sensor sending a fuel trim signal to the ecu, what could cause that? 

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  • 1 month later...

well, bumping my thread here.

 

I ended up taking the car to a local shop, and they told me it was the ecu. 

We popped in a junkyard ecu, and the car started up and ran great for nearly 100 miles.

I drove it to the store, and when I came back out to start it, I got the same two clicks at the relay. on/off- no power to the pump.

Never threw a code.

 

I'm wondering if I have a bad ground to the relay, or maybe the power line is getting grounded out?

Seems weird that the new ecu "fixed it" for 92 miles

 

Any thoughts?

 

I'm thinking of running power from my cigarette lighter to the fuel pump, just so the car can still drive around. 

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  • 2 weeks later...

Well, I'm probably the only one reading this, but in case someone else has the same issue I wanted to update the thread.

Kinda bummed no one could offer more advise, but maybe no one else has experienced this problem....

 

The fuel pump relay on this car has 4 pins.

 

1.) 12v power to the relay from the ignition switch (no power until the key is turned)

2.) a ground 

3.) 12v constant power from the battery ( this 12v is supplied all the time)

4.) power out- to the fuel pump.

 

The way it works is, when your ignition is turned on, it completes a circuit with the ground, flipping the relay to bridge the connection from the  12v constant battery lead to the power out. In return this sends power from your battery directly to your fuel pump. 

 

My issue was the lack of ground. The computer provides the ground to the relay.

 

Since my old computer and my new computer won't consistently provide ground, I'm still stumped as to what is going on here... 

The computer never threw a code, and I replaced all sensors related to fuel trim in efforts to figure out the issue. That turned out to just be a waste of money.  

I read about some wrx guys wiring their fuel pump to be running all the time while the car is on, so that is what I did. 

I don't think this will result in any negative issues, but if you know something I don't please chime in.

 

Since I wasn't getting ground from the computer, I cut that wire and sent a new wire to the relay that is grounded out on the chassis.

now as soon as I have the key in the on position my fuel pump is pumping fuel. It seems to rev hire and be more responsive, even though that was not my objective.  :headbang:

 

My fuel pump relay is still getting pretty hot which indicates a poor connection. I am going to go ahead and replace it. I'm thinking all this troubleshooting has probably had its fair share of wear on this poor little relay.  

 

I hope this helps someone. If you experience the same problem, and figure out a proper solution, let me know. I will update this if my "repair" fails. 

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  • 4 weeks later...

Final verdict- poor connection at fuel pump caused intermittent fuel cut off. The poor connection may of also contributed to the excessive heat on the fuel pump relay.  

 

Of course this was a secondary issue to the lack of ground at the relay. That will have to remain a mystery....

 

I hope this helps someone. I post in the historic section of the forum too, as I have a 1980 Brat. There must just not be many active members on here. I figured if I kept following up and continued to post updates on the thread that it may pop up in searches easier. 

 

Best of luck to anyone who encounters fuel delivery issues.

 

My advice would be the following:

 

remove the fuel line after your fuel filter. turn the key on and see if you have any fuel flow. 

 

If no, try removing the fuel line where it goes into the fuel filter. Does it flow here? this means you have a clogged fuel filter. replace that and you are good to go!

 

If you lack fuel flow to the filter, try your relay. 

 

This is located under the dash. It is a small silver cylinder with a green plug going into it. 

 

 

Disconnect it, and use your multimeter to confirm you have the following at the plug receptacle:

 

1.)  A constant ground

2.)  A 12v that comes on when the key is "on"

3.) constant 12v from your battery

4.) the fourth pin is a red and black wire that powers your pump. Make sure that you have 0 resistance to ground (no continuity (no short!)) 

 

 

If all of these are present, remove your fuel pump cover. This is located under the rear passenger seat, beneath a rubber cover. 4 phillips head screw are all you need to remove this. 

 

Here you will find a 6 pin connector that plugs into the pump. With your relay plugged back in, and the key in the "on" position, listen for a whining sound. If all is functioning properly you will here your fuel pump running. If no sound, try wiggling the plug back and forth gently, and listen for your pump to turn on. If this doesn't happen your fuel pump is probably dead. In my experience it is difficult to check for voltage at the pump. The pins are very tiny, and with my quality multi meter, I couldn't get a good reading. 

 

Lastly, if you have to replace/remove the fuel pump be VERY careful with the plastic nipples that the hoses plug into. These have likely become very dry and fragile over the years. If they break, then you will be spending $400 for a new unit, as opposed to $100~ for just the pump. Unfortunately I broke mine, and all the ones at pick n pull were either missing, or broke in the same spot... 

 

Good Luck!

 

-Hunter

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