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Discussion Starter · #1 ·
Fuel pump relay has been checked out and is working as it should . There is power out of the relay but no power to the pumps after engine runs for a few seconds. Something between the relay and the pumps is cutting power off to the pumps. If I run a jumper form the battery to the pumps the engine runs great. I am considering running a new wire from the relay to the pumps. This will power them only when the the key is in run or start position. Can anyone tell me if could cause other problems by doing this.
 

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But Mad North-Northwest
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You've got to tell us the year and model of your car, Terry. Otherwise nobody's going to be able to help you. Best to put that in your sig.
 

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Discussion Starter · #5 ·
L-jetronic Spider? Be aware the drive relay also functions as a safety device - it will cut power to the fuel pumps in the event of a stall (as might occur in an accident).
L-jetronic Spider? Be aware the drive relay also functions as a safety device - it will cut power to the fuel pumps in the event of a stall (as might occur in an accident).
Is it possible the drive relay is the problem with lost of power?
 

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But Mad North-Northwest
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Okay, I saw your other post: '87 Spider. I don't have a wiring diagram for an '87 but I'll send you one for an '86 that should be pretty much the same.

Are you checking the output of the main relay or the drive relay? The drive relay powers the pumps and there's nothing between it and the pumps, so it's hard to see how you could have power on terminal 87 there and then the pumps stop running. I think you've possibly got an issue with the triggering of the drive relay, but I'm not an expert on that.
 

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The fuel pumps get power under two conditions. 1) the engine is running - the drive relay gets a signal via a sense wire at the coil or B) the key is in the start position which bypasses the drive relay to ensure the pumps get power during cranking. So, if it starts then dies after a few seconds either the drive relay is faulty or the sense wire is faulty. Check (clean) all the connections at the coil.
 

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Possible fuel pump relay under parcel shelf. Big rectangle black relay. You can bypass it to see if pump works. I don't remember which terminals to use so hopefully someone else will chime in.
 

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For testing purposes only you can remove the drive relay (the larger one) and fashion a jumper wire to connect where the relay terminals 30 & 87 would plug in. If it then starts & runs the drive relay is likely faulty. It is not safe to continue to drive the car with such a jumper wire in place - the drive relay also functions as a safety device - see reply #3 above.

Note that there are replacement non-Bosch brand drive relays that 'fit'. But they may lack the safety aspect of cutting off power to the fuel pumps in the event of a stall.
 
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