BMW startup mystery

I have a 95 BMW 525i that has had a particular problem since I bought the car in 1997. If I start the engine, run it for just a few seconds (like it would take to move the car from the driveway into the garage), then shut it off, the next time I try to start it, either a few minutes or even a few days later, it refuses to start until I crank the engine for 20-30 minutes. Otherwise the car runs perfectly and passes all California emissions tests. Can anyone explain this to me? What needs to be done to solve this problem (other than “don’t do that”). Thanks!

“until I crank the engine for 20-30 minutes”

Did you mean 20-30 seconds???

No. 20-30 minutes.


That’s not possible. Your battery would be dead long before that and other parts would probably fry.

That is a strange one alright but it should be fairly easy to find the trouble since you can count on it going bad. You need to see if the engine is getting spark and fuel when this happens. There may be a faulty relay involved. You could try spraying some starter fluid into the intake and see what happens. If the engine fires right up you have some sort of fuel delivery problem. If not, the ignition is most likely at fault.

Like Cougar said, it sounds like something electrical (like a bad relay) preventing either spark or fuel delivery. Do you have a mechanic you trust?

Next time this happens, push the gas pedal all the way to the floor while cranking the car. See if it starts any quicker that way. It sounds like maybe it is flooding from the excess fuel left over from the last cold start/shutdown.

Also, regardless of what you do, do NOT crank a car for those extended periods. You are wearing out some very expensive equipment doing that. If this is repeatable, like you say, a good BMW mechanic should be able to solve it quickly.

Very good thought there Tardis.

The car is sitting at a mechanic’s shop now due to a water pump problem that developed last weekend. I had the car towed to the shop and after the tow truck driver set it down I foolishly forgot this problem and started it for 5 seconds to pull it into a parking space, then turned it off. When the mechanic tried to move it on Monday it wouldn’t start. He says he was able to start it by squirting starter fluid into the air intake, but it would only run until it burned up the fluid. So it sounds like a fuel delivery problem, but this car has done this since I bought it in 1997. The fuel pump works fine 99.999% of the time. I think there may be some problem between the computer and one of the sensors- maybe the computer thinks the thing has too much fuel and is cutting off the fuel flow. When the car eventually restarts- as I said before after 20-30 minutes of on and off cranking, it runs rough initially then smooths out in about 30 seconds like nothing happened.

Anyone in the Riverside area want to buy a BMW cheap? Body, glass, tires, wheels, etc. all good!

OK, on and off cranking for 20-30 minutes, and no, the battery doesn’t go dead.

I have tried that in the past and it has never made any difference either way.

Unfortunately, besides the work I have done myself in the last couple years (new struts all around, new starter, water pump, oil cover gasket, headlamp housing) etc., I’ve also dropped $2K for a transmission rebuild because of leaky seals, the power locks are flaky, two of the windows no longer operate, the license plate lamp has not been working for two years or so, and the driver’s head restraint motor is dead. A good BMW mechanic would cost more to look at the car than it is worth. I think it is time to just write it off as the POS that it is. Expensive lesson learned- never keep a BMW beyond the warranty period!

I am thinking fuel pump problem, is vaporlock possible with FI? 10 to 12 seconds max cranking has always been my rule of thumb. Wondering if you just had the car in the on position listen for fuel pump, if you can hear it wait till fuel pump achieves pressure and stops, then try cranking?

Well, before you write off the car over what may just be a bad relay, post this (with a very complete description of what it’s doing) in several BMW forums, see what they say. You may get lucky.

You stated that the engine fired up ok using the starter fluid and then died again. This would mean that the fuel pump is most likely not getting power and the fuel pump relay is suspect. I don’t know how the circuit for the pump is designed but I doubt there is any signal from the engine control that is turning the pump off. I suggest you replace the fuel pump relay to see if that clears the trouble. By checking the voltages on the relay you could verify that it is, or isn’t, the trouble.

“The mechanic sprayed starting fluid into the intake to get it started” say fuel system problem, maybe. Unless your mechanic is one who says, “I know all that stuff”, here is a good article on how to test a fuel pump in ways more than a static pressure check:
Another thing to check are the engine coolant temperature sensor, and the intake air temperature sensor. Usually, they cause a too rich mixture; but, I’m sure they can cause a too lean mixture, also.
To “prime the fuel pump” turn the ignition key to ON for two seconds, off for fie seconds, ON for two seconds, off, ON, off, ON, start.