No current going to transfer fuel pump?

[marsgorski]

I've been having fuel-related issues (you can read more about it here), and today I performed a pressure test on the transfer pump (the low pressure pump in the tank that feeds the main pump) and I got zero pressure.

I do hear a whirring sound coming from both the main pump and the transfer pump.

Next I checked current from the wire connector to the pump's connector and I read 0 amps. I also checked voltage across the two terminals in the wire connector and got 0V. Just to make sure my ammeter was working and I had it in the right settings I tested both of those things on the fuel relay connector and there a got positive readings (1.4A and 12-13V)

I still don't fully trust my current and voltage measurements since I did hear a whirring sound. Is there another way I could test the electrical component of the fuel system? I wanna make sure that part of the system is working correctly before throwing in a new fuel pump.

[325e '87]

Do you have a Bentley manual? There’s a free e copy of it around.

It has test procedures for the fuel system. I haven’t had to mess with mine much but i think there are two relays under the hood that can be swapped for a quick diagnosis (swap, test, swap back, test).

You could have a bad relay, crank sensor, pump, filter, or debris in the tank.

[marsgorski]

I do have a Bentley Manual. But I seem to have reached a dead end on the manual. It basically tells me to check the pressure at the transfer pump. If it is low, then check the current. If the current is too high (in my case it's zero) then pull out the pump and clean it. Check the pressure again and if it's still too low, replace the pump. Nothing about what to do if there is no current.

[325e '87]

Somewhere in the manual it tells which prongs in the relay socket to jump to artificially run the system without turning the engine over. It really helps when you’re trying to test pressure, or diagnose electrical issues. I will try to find it today.

[marsgorski]

Somewhere in the manual it tells which prongs in the relay socket to jump to artificially run the system without turning the engine over. It really helps when you’re trying to test pressure, or diagnose electrical issues. I will try to find it today.

I did run the system that way. That’s when I was able to clearly hear the whirring sounds coming from the pumps.


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[jbontke]

I did run the system that way. That’s when I was able to clearly hear the whirring sounds coming from the pumps.


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You can apply 12v from one of the unused fuse terminals (in the fuse box) that read 12v with ignition on.

I ran a jumper wire that has a 15amp fuse to connect from the 12v ign on to the fuel pump fuse (#11). Connect to the #11 fuse connection closest to the outside of the box. The Fuel pump replay sends power to the fuse block, through the relay, and then on to the pumps. The fuel pump will run as soon as the key is in the run position.

[TobyB]

ASSuming you have an earlier car, from memory there is only one pump circuit, and it
splits at the wiring loom near the tank. So if the main pump's got voltage and the
aux pump does not, it's a local wiring problem. Make sure the grounds are really
ground, too.

The noise makes me suspect that maybe something goofy is going on with your meter...
...but it's hard to tell over the internets.

http://www.wedophones.com/BMWManualsLead.htm

for wiring diagrams.

t