2002 525i cranks but will not start (intermittent problem)

[musikkant]

Hi,

I am new here and was referred to this forum by a friend. I recently moved from Washington D.C. to Florida and am enjoying the weather. However, I have an issue with my 525i.

This has been ongoing for a couple of years and is intermittent. About 5-6 times a month (sometimes more often, sometimes less), the car refuses to start when I turn the key. The starter turns over at regular speed, so it does not sound like a battery issue. Instead, I have thought it is a fuel or ignition issue. The car will sometimes start up after a few minutes of simply just waiting. Other times, it takes much longer, even hours. However, the car will start again after I wait long enough.

I had a BMW mechanic in D.C. look over my car before I moved to Florida (change brakes, fluids, etc.), and told him about this failure to start issue. Of course, when he worked on the car, the car started just fine. However, when I picked up the car, it happened. After listening to it, he was puzzled. He thought it may be the fuel pump, so he pounded on it with his hand while I tried starting the car. It did not help. So, he thought the fuel pump may be ok, and that it would be an ignition problem. He thought perhaps the key recognition system in the ignition may be faulty and not recognize the key properly. However, I have had this issue with all of my keys, including the valet key, so I am not sure that it is the issue. After we had worked over the car for 15 -20 minutes, it suddenly started up again. The mechanic was perplexed, and I was out of luck trying to fix it.

So, is this something anyone else has experienced?

Thanks!

K.

[randomloop]

Check your MAF sensor.

My daughter's 525i had a similar problem. It was intermittent at first, and then gradually became persistent.

We went through the fuel pump, filter, plugs, ignition/fuel routine too.

In frustration, I just started to unplug the sensors to see if 'anything' would work. Unplugging the MAF sensor seemed to do it. We replaced it and haven't had any problems since.

You don't mention if you have any indicator lights on your dash or if your mechanic has read any codes stored in your computer. check those first. We had an O2 sensor code that wasn't really an O2 sensor code, but it helped narrow our search (yeah, we replaced to O2 sensor too).

Good luck.

[musikkant]

Thanks for the response. I will check into those things. It's just so difficult figuring out something so intermittent!