Fuel pump not getting voltage.

UK forum for general and technical discussion about the Z3 roadster
Post Reply
Joined: Sun 05 Jun, 2022 23:16
Posts: 1

  Z3 roadster 3.0i

Fuel pump not getting voltage.

Post by rpyount25 »

Hello all, I'm a Texas based owner of a Dakar yellow z3 3.0 w/ 100k miles. I purchased the car from my neighbor about a year ago. It was running well before he let it sit a couple months. I believed the fuel sender was the issue as it wouldn't start or show any fuel despite the tank being full.

Long story short before I ordered a new sending unit, the connector to the pump was receiving voltage. After a few more months of it sitting I was finally able to install the new unit, but now I have no voltage to the pump? I reset the immobilizer, checked the fuel pump fuses, getting ready to test the fuel pump relay with a jumper per pelican parts troubleshooting page. I've read a few posts on here saying to check the MAF and Crank position sensor. Are there any other reasons why the pump wouldn't be getting voltage before I dump more parts into it?

Any help or suggestions would be appreciated, I'm not used to working on BMW's, but I'm ready to get her back on the road. Thanks!
Joined: Mon 12 Nov, 2018 17:47
Posts: 126

  Z3 roadster 2.8

Re: Fuel pump not getting voltage.

Post by LaRy »

Hi, is everything else working? 'm looking at a 1998 electric drawing.
Do you have the feeling that the DME/ECM Engine module is alive? Remeber taht these cars are now so old that the relays get broken just by age.
Anyway, if everything is ok, you have a relay called engine control moduel relay, probaly found in the left side close to the DME (also called ECM).
This relay, if activated, is supplying voltage to fuse F13. Fuse F18 should continoulsy have voltage. These fuses are called fuel pump fuses. One fuse supplying the fuel pump motor relay is continously hot, and the other is hot when the engine control relay is activated.
If those two are hot (and fuses ok) the fuel pump relay is supposed to be activated.
But to make this happen, also the negative side of the fuel pump motor relay must be grounded by the ECM transistor output. If not, it's something from the ECM stopping the pump relay and motor to start.

Look at the fuel pump relay, make a jumper between terminal 30 and 87, pump should start. Check if you have 12 volt between 86 and 85. Check if you have 12 volt between 86 and ground.
Post Reply