Help with external fuel pump

[jimmyleg325e]

Hey E30 experts, i need a bit of help figuring this out. Car is an 86 325e. Everything was working great but my fuel pump whine was getting really bad. Decided to swap it for a new Bosch unit. Disconnected battery, pulled fuse 11, replaced pump. Primed it as directed. Car wouldn’t start, lots of attempts. Fuse ok, swapped the relay just in case. Still nothing. I bench tested the new pump so I know that's not the problem.
Inspected the wiring and found a torn boot and some corrosion on the positive connection. Trimmed the wire back a bit and replaced that connector. Still nothing. Got back under it and replaced the ground connector too. At this point I used a multimeter and was getting nothing from the two connections when partially turning ignition.
Wires look fine, they come up through the floor under the seat.
Power is getting to the Relay and when I jumped terminals 85 and 86, still no power to the pump wires.


Not sure how I screwed this up so bad. Seemed like an easy job. Any advice greatly appreciated.

IMG_8861.jpg

[msservices]

You did not mention putting the fuse back

[jimmyleg325e]

Lol, yes fuse went back.

[superj]

its something dumb. you didn't do anything out of the ordinary. the only thing I would do different is unhook the battery instead of pull the fuse. I have fried to much stuff in the past by not unhooking the battery.


I would check every fuse now. just pull each one, one at a time, and verify they are all still good. after that, pop the little relay cover by the afm and swap the two relays that look the same (if I remember right, they are but you can check the little diagram on the side or bottom to verify)

[marsgorski]

Hey E30 experts, i need a bit of help figuring this out. Car is an 86 325e. Everything was working great but my fuel pump whine was getting really bad. Decided to swap it for a new Bosch unit. Disconnected battery, pulled fuse 11, replaced pump. Primed it as directed. Car wouldn’t start, lots of attempts. Fuse ok, swapped the relay just in case. Still nothing. I bench tested the new pump so I know that's not the problem.
Inspected the wiring and found a torn boot and some corrosion on the positive connection. Trimmed the wire back a bit and replaced that connector. Still nothing. Got back under it and replaced the ground connector too. At this point I used a multimeter and was getting nothing from the two connections when partially turning ignition.
Wires look fine, they come up through the floor under the seat.
Power is getting to the Relay and when I jumped terminals 85 and 86, still no power to the pump wires.


Not sure how I screwed this up so bad. Seemed like an easy job. Any advice greatly appreciated.

IMG_8861.jpg

I am having similar issues regarding current getting to my fuel pump (I wrote about it here).

I have a suggestion that might help you and also a question that might help me. My suggestion is that you might be looking at the wrong relay or at least wrong relay terminals. According to the Bentley manual to test the pump you should jump terminals 30 and 87 on the main relay. Another source of information (can't remember which now) advised me to check terminals 30 and 87 on the pump relay.

And my question is how did you bench test your new fuel pump? I bought an aftermarket TRE Performance pump to replace both my transfer pump and the external pump, and I would like to test it, as well as the old pumps. I suspect that the pumps may not be at fault in my case, but that there may be a wiring/grounding problem. Another question I have is where is the ground connection for the pumps located?

[superj]

Just hook power and ground to the plug to bench test. Or hook power and ground directly to the solder joints on top of the actual motor to power it up

[jimmyleg325e]

Thanks Marsgorski, I'm still tinkering with things trying to sort out the problem. I'll check those relay terminals again. I have found another thing that I'm sure is pointing to the problem. If I disconnect the power to the in tank fuel pump and then reconnect it, the car will start but die again. So I'm now testing the in tank pump to see if it's getting the power it needs. I'm not completely clear on the wiring though, I wonder if the power needs to go to the in tank pump before going to inline pump. Will one run without the other? Either way, I'll find it eventually. I always dreaded electrical problems with this car and knew I it was only a matter of time.

I tested the inline pump with jumper cables in the trunk. I know it's a bad idea to run them dry so I only touched the power to it for a second to confirm it worked. So quiet compared to the racket my old one made. I guess the in tank one could be tested with a meter, measuring resistance.

[jbontke]

I have a 09/86 325e and the wiring for both pumps is tied together connected. I have an in tank TRE pump that runs without the wires on the inline pump (wires in the first posts picture) connected. My car sat for a year. I had an issue where the car would start then die. If i pinched the fuel return line it would run, but the fuel pressure was above 100 psi. I pulled the injectors, cleaned them, replaced the screens, tested the resistance, and the car started up and ran.

[msservices]

Okay, so if the pumps are wired together, then if one of the pumps was creating a short, could it create the illusion that the other pump is not getting power when hooked up?

[superj]

it would for sure send the power down the easiest path to ground. electricity is lazy, it wants the path of least resistance

[jbontke]

Okay, so if the pumps are wired together, then if one of the pumps was creating a short, could it create the illusion that the other pump is not getting power when hooked up?

A short as in a blown fuse?? That would cause both pumps to not work. If the wire/circuit was broken before where the pump sires split, then it would kill both pumps. If the wire/circuit was broken after the split, it would affect one pump. I would test the leads at the pump, if you get ~12v, it will power the pump. I am guessing the OP would need to test resistance from the pumps 12v+ wires to the relay and fromt he 12v- to the frame to be sure they are not open.