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Discussion Starter · #1 ·
This one is driving me nuts. :( Originally thought I had a bad fuel pump. Key on, fuel pump winds up to pressure system is the way it should work. It has been working fine until about 2 weeks ago. Now I get 12v down to the final fuel pump connector (in the tank). Great-after a few seconds, the system times out then the power is removed from the pump (I believe this is normal?) My meter shows I have the 12v. Now when I connect the fuel pump the 12v disappears! I finally just jumpered the pump to the battery and it runs fine.

My factory manual indicates that the power source for this is through the relay from the Engine Control Unit. Relay tests good. So I am down to the ECU.

Now can not find anything anywhere on the net that shows ECU for the 625i gator, but I have found a Relay Control Module (AM144734). Question 1, Is this the same thing? Question 2, has anyone else ran into this problem and how did they resolve it? Many Thanks
 

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just a suggestion, you say when you bypass the wiring and relay with a direct connection to the battery it runs fine.

Did you follow the wiring harness to see if a wire got cut / frayed / shorting out, having 12v doesn't mean enough amperage can flow to run the fuel pump.
 

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Discussion Starter · #3 ·
Vanishing Voltage

I think I may have found the problem. There are two engine control relays K45). The first (top one on the diagram) seems OK, the bottom one seems to be the culprit. Voltage in, nothing out. I jumpered the contacts for the fuel pump from this relay and the relay came on. Ordered 2 new relays from Ebay, used. These are the same relays used nn some of the Subaru cars. Very $$$$. May just get a standard 12v relay to test.
 

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Discussion Starter · #4 ·
Confirmed. It was the bottom relay (as shown in the factory manual for the engine control relays K45). Since I did not have a direct replacement, wired in a 12v relay I did have. Started on first crank!
 

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Same problem

My 625i has this same issue. I have an extensive technical background and haven't been animal to trace the issue. It definitely acts like a bad relay. Very frustrating. Are the Subaru relays you replace them with perfect matches and do they go into the relay board under the dash?. Thanks for any help from anyone.
 

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Discussion Starter · #6 ·
Vanishing Voltage

There are two relays are located under the seat, passenger side. They are mounted to the frame towards the middle back and have rubber boots holding them in place. I just rewired a heavy duty relay in place of the one that goes directly to the fuel pump in the tank. It worked so well that I have left it in place and have not had any problem since.
 

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Many thanks

I can't tell you how much I appreciate your help with this issue. I found the relay. Two days later the fuel pump wouldn't engage. I flipped up the seat, tapped the relay and voilà, it tripped and the pump engaged. Great job tracking down this problem. Thank you again
 
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