A question about fuel pump relays

[flyboyx]

ok. so....if you are doing a 24v swap into an m20 car, the fuel pump relay is located on a bracket by the afm or the air box and attached to the engine harness.

if you are doing a 24v swap into an m42 car, the fuel pump relay is located on the firewall to the right of the c101 plug, also attached to the engine wiring harness.

basically, my point is that you completely eliminate the fuel pump relay by doing the swap because (at least in my case) this component is located on the 2000 mz3 body harness and not the engine wiring. i thought it seemed kind of dumb to connect a 15 amp wire(body side e30) to a tiny little 5 amp wire from the s52 harness.

i have been getting a fuel pump relay code so i figured this out today by studying my etms. assuming this to be the case with all e34/36 engines, i can't figure how in the hell anyone can do a swap and get fuel to the engine the way all of the online wiring diagrams are written?

don't get me wrong, since i figured out what is going on, it will be an easy fix to simply add a relay in the circuit. a side benefit is that i probably won't have to sit there and listen to fuel rushing though the fuel loop at 50 psi when the key is in the accessory position.

[MattM]

it was on my M50's engine harness, just like the M20 there are 3 relays on the main engine harness...
M50 from a 92 525i

[Harvester]

I have an issue with my swaps (M50) fuel pump relay. I can jump the pins on the relay plug to get the fuel pump to turn on, but no power from the ignition to turn the pump on.

Followed the wiring chart to the letter (or pin number) and all wire colors matched up. Not sure if there is something under the dash that needs tweaking too?

Any ideas!

[flyboyx]

I have an issue with my swaps (M50) fuel pump relay. I can jump the pins on the relay plug to get the fuel pump to turn on, but no power from the ignition to turn the pump on.

Followed the wiring chart to the letter (or pin number) and all wire colors matched up. Not sure if there is something under the dash that needs tweaking too?

Any ideas!

ok, i don't mind the thread jack. there are 4 wires that go to the fuel pump. two small wires and two large. the two small wires function to power up a little electromagnetic coil in the relay that closes a set of contacts which allows a complete circuit between the two large wires. this is how a relay functions.

one of the little wires should go to 12v power in the fuse box with a 5 or 10 amp fuse. the other small wire should go to the ecu which basically has an electrical switch that completes the small circuit to close the relay. this circuit has to work before before 12v power will go to your fuel pump.

of the two larger wires, one comes from 12v 15 amp power in the fuse box and the other wire travels directly to the fuel pump.

all four wires have to be connected properly for the circuit to work.