I knew it had to happen to me sooner or later, and it did: as I left the grocery store heading home, my 21-year-old BMW did not start. A nice lady asked me if I needed help to jump the car, and I had to decline her offer; it wasn’t the battery, it had to be something else. Good thing the store was only a few blocks away from home. I had the car towed the next day, pushed it into my garage and started debugging.
There’s a straightforward step-by-step procedure you can follow to find the cause of a non-start. After eliminating the obvious suspects – a dead battery and the absence of spark – the most obvious component that needs to be tested is the fuel pump. In later E30 models (starting with production month 9/87) there is only a single fuel pump, located in the fuel tank, accessible through a hatch under the passenger’s side rear seat. It’s easy to check if the pump is working: remove the rear seat, remove the pump cover, crank up the car (or have a helper turn the key instead) and listen. The pump should make… well, pumping sounds, just as you imagine a fuel pump would sound. If you can’t hear anything it could mean that:
- Either the pump is broken and you need a new one, or
- You have no voltage at the pump – because either the wires are interrupted (pray that they aren’t because fixing wiring in a car is a terrible job) or your fuel pump relay is bad
To check for voltage remove the power connector from the pump, stick the probes of a voltmeter in the connector and crank the car – if the relay works the probe should show battery voltage, about 12V. Operating the ignition while holding the probe in the connector and reading the voltmeter display can be a pretty cumbersome task - another set of hands greatly helps. If you’re working alone you can simplify your life if you bypass the relay: remove it from its socket and link the connector’s pins 30 and 87 together with a wire (preferably a fuse holder with a 15amp fuse); this will bypass the ignition and supply constant battery power to the fuel pump (that’s also a good way to make sure the wiring is fine).
If there’s voltage at the fuel pump but the pump is silent it’s time for a new pump. There are a few models for sale that can fit the E30. The OEM pump for the ’88 E30 is a VDO. The good thing about it is that it comes with the complete assembly: fuel pump, mounting frame, filter and O-ring; you just swap the old one out and re-connect the hose. The average price online for this OEM part is about $200. The cheapest I could find it for was $176.35 at autohausaz.com. Unexpectedly, my usual supplier bavauto.com sells the VDO pump for an ungodly $362.95.
This is the whole procedure, step by step. Click on each picture to see a larger version and access the image notes. Click here for the whole set.
The Bentley recommends disconnecting the battery (as it does for almost every procedure); I didn’t. Anyway, be careful when you work around fuel lines. Don’t smoke.
Insert the whole assembly with the new O-ring back in the tank. I couldn’t find an O-ring of the same size in any automotive shop and the local BMW dealer didn’t have one in stock so I decided to re-use the old O-ring. Let posterity judge me…
Reconnect and install the other pieces in the order they were disassembled.
Work time: about three hours.
After I completed the procedure, the car started immediately, as expected. I have not noticed any unpleasant noise when the pump is in operation. Now I can only hope that this new pump will last as long as the original one did...