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Fuel Pump Mystery


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7 replies to this topic

#1 quartus

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Posted 14 September 2009 - 01:58 PM

Has anyone have any solutions/theories to the following:
I just brought a 86 GL-10 Turbo 4x4 project car, EA82 MPFI with 5sp man trans. Here's the mystery, it wasn't running when i got it but 3rd party troubleshooting narrowed it down to faulty fuel pump. I got a new fuel pump and the car still wouldn't start, I wasn't sure if the pump was primed so I disconnected line at the fuel filter and jumped 12v straight to pump. That filled the line & more :)
I then started the car with the pump still direct wired and it was running fine till I heard the pump stop. I then shut off the engine and checked all my connections on my jumper and figured Advance Auto sold me a bad pump, I took the pump back off (opps it was under pressure :eek:) and long story short the pump was good, my jumper was bad.
I reinstalled the pump & jumper and now can't start the car even with the pump running, it doesn't even cough. What do you think I could of done? I'll check for spark tonight with a timing light (the digital tach is indicating so I'm guessing it sees some spark activity). Can you flood the engine if you push on the gas while trying to start it? Is there a important connection near the fuel filter that I could of disturbed? Are there any interlocks/cutoffs I need to know about. I'm @ wits end. I found a EA82 FSM online but I don't have the owners manual for any simple prestart requirements (ie clutch in, trans in neutral before starting).

#2 markjw

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Posted 14 September 2009 - 02:06 PM

Did you check the fuse panel? The one under the dash. Maybe the jumper wire grounded and blew out the Ign./Fuel fuse. Or,some other fuse.

#3 Cougar

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Posted 14 September 2009 - 03:22 PM

If spark is ok then make sure a T-belt didn't break and the rotor in the disty is spinning.

#4 quartus

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Posted 14 September 2009 - 07:13 PM

My horrid jumper strikes again!:mad: It helps if you mark the same wire NEG on both ends instead of different wires. I had the polarity swapped on the pump so I was trying to pump INTO the tank instead of out. Rolled leads and car started right up. Lesson learned; you can lose focus around too many gas fumes :-\
Thanks for replies, the saga can continue on the road to Subaru Fun.

#5 john in KY

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Posted 15 September 2009 - 03:58 AM

Stripped a few of these over the years. Original problem probably a failed relay. Relay is behind the passenger side panel in the back seat area. Real pita to get to because the complete back seat has to come out and those plastic panels can be a bear to pull without breaking. Just throwing this out there if you ever feel a need to truly fix the problem.

#6 quartus

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Posted 05 October 2009 - 01:10 PM

UPDATE: I ended up having to jumper to ground at the pump to keep it running, I'm guessing it has some kind of kill circuit that cuts power to fuel pump if certain conditions aren't met. :confused:

#7 ruparts

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Posted 05 October 2009 - 01:50 PM

UPDATE: I ended up having to jumper to ground at the pump to keep it running, I'm guessing it has some kind of kill circuit that cuts power to fuel pump if certain conditions aren't met. :confused:


The ground circuit is taken care of in the ECM, just run a new ground from the pump and it should be ok.

#8 Cougar

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Posted 05 October 2009 - 03:21 PM

UPDATE: I ended up having to jumper to ground at the pump to keep it running, I'm guessing it has some kind of kill circuit that cuts power to fuel pump if certain conditions aren't met. :confused:


The grounding for the pump is tied through the ECU for safety. If the ECU dosesn't see ignition pulses it will shut the pump down. You don't want to have fuel coming out if an accident happens and could take place if you bypass the safety design.

The ECU problem you are having is fairly common. I have repaired a couple of ECUs with this same trouble. Both of the units had a bad driver transistor for the main output transistor switch that provides the ground switching. Here is a link to a thread that discusses the issue and you may find interesting:
http://www.ultimates...ight=transistor




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