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sprinkles08
sprinkles08, ASE Certified Technician
Category: BMW
Satisfied Customers: 21609
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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Fuel pump works only with jumper wire inside glove box fuse

Customer Question

Fuel pump works only with jumper wire inside glove box fuse panel between 22 & 31. I bought the car like this. Can't find any bad fuses have checked in trunk battery compartment and under passenger cabin air filter compartment. Please advise, much appreciated!
Submitted: 9 months ago.
Category: BMW
Expert:  SuperDave replied 9 months ago.

Is there power at fuse #22? I am assuming not.Fuse #22 is for the fuel pump relay.

Expert:  SuperDave replied 9 months ago.

Sounds like a bad fuel pump relay.By jumping power from fuse#31 to 22 you are bypassing the fuel pump relay.

Expert:  SuperDave replied 9 months ago.

Fuse #22 should have power all the times even with the key off.If not then could be a bad connection behind the fuse box.

Expert:  SuperDave replied 9 months ago.

A bad engine control module relay could also cause no power at fuse#22.

Customer: replied 9 months ago.
I agree that is what I was thinking a bad relay and am unsure which it would be as there are many relay locations throughout the car with several relays.Key off: fuse 22 1.0v fuse 31 0v.
Key on: fuse 22 3.5v fuse 31 12v.
Expert:  SuperDave replied 9 months ago.

There is a small fuse box with 5 fuses in it for the engine electronic.Did you check the fuse there?This is what the fuse box looks like.

Customer: replied 9 months ago.
checked all 5, those are good.
Customer: replied 9 months ago.
Can you tell me the location of the fuel pump relay & ECM relay? Possibly the instructions to test the relay as well? Very much appreciated!
Customer: replied 9 months ago.
Note when the jumper is removed from #22 the dash informational display goes out until jumper is returned.
Customer: replied 9 months ago.
SuperDave, please pass on the question to another technician if you are no longer able to help, very much appreciated!
Expert:  sprinkles08 replied 9 months ago.

Hello and welcome to JustAnswer!

The first thing that will need to be done is test for constant power to the fuel pump relay with the key on. The relay will be in one of two spots. It will either be in a relay box in the right side of the trunk, or it will be in a box just behind and below the glovebox opening.

Customer: replied 9 months ago.
SOLUTION: This car is super clean inside and out, not a mark on the carpet, and the problem was super corroded fuse panel below passenger seat carpet. Picture attached.NOTE: Top mounted wires (majority of them) are actually OK, it's the several which attach on the underside out of view which are the culprit!
Expert:  sprinkles08 replied 9 months ago.

Excellent, I'm glad you found it! That looks pretty bad.

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