5-Series (E12,E28, E34, E39, E60)Chat relating to the BMW 5-Series of all generations. Specific models include: BMW 518, BMW 520, BMW 520i, BMW 530i, BMW 528i, BMW 530i, BMW 518i, BMW 524d, BMW 525i, BMW 525e, BMW 528e, BMW 540i, BMW 535i, BMW 520d, BMW 525td, BMW 525d, BMW 530d, BMW 525i/xi, BMW 530i/xi. (BMW 5-Series Forum)
I would start with electrical. Fuel pump relay is a biggie, I would replace it just to have a spare at least.
I had an 82 528e that I was working on (my GF's 16 year old daughters car), just doing a tune up and stuff. When I finished it would not start! Well, after a half day of technical troubleshooting it turned out to be that when I closed the glovebox it would not start, when I opened it, the car would start. Turns out all the CD's junk etc. in the glovebox were jamming against the computer(ECU) harness (the ECU is above the glovebox). So I removed all the junk, ty-wrapped the harness, reseated the ECU connector and it worked! Check your ECU connector.
Check fuse 1 (16 amp) in your fusebox. Remove it, squeeze the contacts together a little and reinstall. Also clean the contacts. This fuse powers the main and transfer fuel pumps. See if the fuse contacts are dirty/arced. Common problem area. Check all fuses while you're there.
Eliminate electrical areas first, on an older BMW the electrical system is your biggest problem area.
According to the picture in the Bentley book the fuel pump relay is the second one (middle relay) on the right side of the relay panel.
When I say RH side I mean as if you were sitting in the drivers seat, not viewing from front of car.
The relay in front of it is the main relay and the relay behind it is the O2 sensor heater relay.
Unfortunately, the book gives a disclaimer that relay locations are subject to change, and may vary between cars depending on options.
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