I have a 1987 BMW 325ic
Lately when I drive it a short distance it starts loosing power for a second then kicks back in but then totally dies. It starts back up after 20 minutes or longer. Very frustrating!!
My BMW mechanic believes it might be the fuel pump but he can’t tell for sure until the car is broken down in his presence, last time I had it towed to him and it started right up! He said he can replace fuel pump but it would be expensive with no guarantee that it’s the problem.
I love my little car, what do you think of his possible diagnosis?
Thank-you! Sue
I think it is quite likely… but… if he installs a fuel pressure gauge and drives it until it bogs down it will confirm the pump problem rather than guessing.
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He’d probably have to tee in . . . which means he has to have a master fuel pressure test gauge kit . . . I think it’s highly unlikely a 1987 BMW has a fuel pressure test port
My gut feeling is the fuel pump. That type of Bosch pump is also used on SAAB, VW, and other Euro cars and they do take a beating.
I have a habit of tearing things apart to find out why a part failed.I’ve cut open probably half a dozen Bosch pumps and the failure cause was always the same.
The commutator on the armature shaft was not just worn, but badly worn. That affects the contact between the commutator segments and the brushes which can make it a sort of fine one moment; acting up the next kind of thing.
The first thing to determine is whether the problem is spark or fuel. Either have your shop hook up a fuel pressure gauge you can monitor while driving, or have them show you how to test for spark, which you can do at the side of the road when the problem happens. The fuel pump possibility has been explained above. Common causes for intermittent no spark are the crank position sensor, ignition coil, ignition switch, faulty fuse, and battery/connection problems.
If you normally drive with a set of keys on a key ring attached to the ignition key, try driving with just the single key instead; i.e. remove it from the key ring. Sometimes dangling keys will wriggle a worn ignition switch to “off” during turns or going over bumps. Seems unlikely given the 20 minute wait before it will start again, but easy enough to try.
Thank-you!! So it’s possible it could stop running and start back up several minutes later?
I’ve heard of that happening to someone when they were on the freeway and it turned out to be their fuel pump. It could be that the fuel pump is going out and if it is will eventually stop working altogether if it isn’t replaced. You can do it yourself if you find the information online. Considering the age of the vehicle the fuel pump could have tons of miles on it.
If you do it yourself it wouldn’t hurt to replace it anyway for $50-60.
I know nothing about cars, my BMW mechanic said it could cost 4-5 hundred plus he said it has a “2nd” fuel pump? That would have to be replaced at same time.
Here’s someone who explained how to replace a fuel pump and filter on a similar car to yours with the same issue though his ended up being the “fuseable link near the battery” as he explains in the first comment reply.
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The fuel pump and fuel filter look like it’s just disconnect the hoses and wires then reconnecting them to the new ones.
Personally I’d start by replacing the fuel pump and filter myself from information obtained online.
fyi OP, there’s two fuel pumps on this vehicle. For an oem replacement pump , expect around $450 parts cost, plus 2 hours labor. Not seeing any replacement cost info for the aux pump, but I’d guess it would be around $200 for the part and another 1-2 hours labor. A diyer wouldn’t replace both, they’d replace the main pump only first, then the second one of that didn’t fix it. But when paying shop prices it’s probably more economical to replace both at once. That is if it isknown for certain that one or both of the fuel pumps are the problem. At this point I don’t think that is known for sure.
A faulty crankshaft position sensor can cause the problem you describe.
Tester
There are a number of hit and miss things which can cause a car to quit one minute and be fine the next. The crank sensor is definitely one of them.
I only mentioned my experience with fuel pumps since the BMW mechanic suggested it and due to my cutting a number of old pumps open to take a look and verify that was the problem. And yes, a badly worn commutator on the pump armature can cause it to quit one minute and run fine a minute later.
Is this a “hit the gas tank with a rubber mallet or 2X4 and try again” situation?
Thx so much!!! I’ll show notes to my mechanic and hopefully he won’t have attitude for me seeking advice from someone else!!