1986 BMW 528



June, 23, 2008 AT 9:16 PM

Engine Mechanical problem
1986 BMW 528 6 cyl Two Wheel Drive Automatic 166463 miles

my 86 528e won't start.

I have fuel and ignition. This problem was intermittent for a long while. Then one day I was climbing a 20 degree bridge and it stalled. I let it coast over the top and it started again approximately at the same longitude going down the other side. The tank read 1/2 so I filled it. But the same thing happened on the way home with a full tank. This time it wouldn't start for a while. I pulled over, jumped the fuel pump at the fuse box and it seemed to work. That was the last time the car was off my property. I didn't trust it after that and when I tried to start it most of the time it would not. Not even sputter.
At one point I pulled the plugs, cleaned them and it started and ran fine long enough to give it a bath. I parked it for a few days and tried it again, no soap. I gave up on it and drove my truck for a while and searched for a mechanic who acted like they knew what to look for, without success. My experience in this town is they are more than happy to charge you for leaning over your fenders and shaking their heads.

Finally it's been sitting for a couple years now; as a result of the no start condition, So I bought a newer 530iA, which is somewhat disappointing considering it cost a hundred times more than the 528. I miss the 528. I'd like to get it running again.
I have owned service garages when I was young an good-looking but now I'm old it's tough to bend and crawl. So I need to focus on the most likely problems or run out of steam without any success.

Fuel flows from the pump and the plugs fire. When this car starts it starts in one or two seconds, never cranked and cranked. I'm a little worried I'll burn out the starter if I don't get direction soon.

What do I need to fix it? I'm thinking of getting a running parts car and swapping parts till it starts. I'm wondering if there's a better way first? thanks


6 Answers


Dr. Hagerty

June, 23, 2008 AT 11:26 PM

There is a piece that is welded onto the ring gear that rotates past the cylinder identification sensor that breaks off and causes this issue. To diagnose, get the car up in the air and take off the plastic grill that is at the bottom of the bell housing, then, slowly rotate the motor till you see the welded spot where there should be a tab of metal, then you will know. I usually move the sway bar out of the way and MIG weld a piece back on, it sure beats pulling the transmission and replacing the ring gear!



June, 25, 2008 AT 1:36 PM

I suppose this piece you refer to can become loose and cause an intermittent problem as well?

What does this part do exactly? Sounds like it determines which cylinder to fire when. Wouldn't this cause a backfire upon failing?

Dragging the car somewhere to get it up on a lift would require an investment of hundreds of dollars. I would like to be a bit more certain before making this investment.

The car would start and run, but on a hot day if I shut it off like at a store. It would start hard or not at all for an hour or so. Suggesting it cooled down and would run again.

Then stalling while running only happened going up a very steep bridge, like 15 degrees maybe. Suggesting the fuel pump might have been stressed or the fuel float malfunctioning.

It didn't just quit permenently. Once I was trying to start it and it didn't even sputter. So I pulled the plugs, cleaned them, and it started up fine. I shut it off and it started two or three more times. Drove in a few yards, gave it a bath, started it put it back in the car port and left it a couple days. Then it didn't start for a year. Then one day I charged the battery and varroom, it started up ran a little rough an quit. I believe that was the last time it ran. Seems like an electronic fault to me. Like a cold start switch that is on it's last legs maybe?

The books I've found give only superficial information. I know a lot about some cars and they all have their quirks. If it were a GM 350, I'd change the fuel filters. I've looked for such a thing on this car but can't seem to locate them. I figure a good BMW man would have two or three good possiblities. Do you fall into this category?


Dr Thom


Dr. Hagerty

June, 25, 2008 AT 3:37 PM

The procedure for finding the problem would be to eliminate from the list what is working, and focus on what isn't. The tab I referred to is the cylinder identification sensor, it's job is to assign #1 cylinder so the ignition is timed correctly. After start up it's up to the revolution sensor to supply that information. An inspection of this tab that is welded to the ring gear is to eliminate the possibility of it failing to be there. Sometimes you can spend all day with a car just to find out it is something simple, like bad or no fuel or poor or no spark. So lets start with this one thing and then we can move to something else like a failed relay or a loose wire or an intermittent crank speed/position sensor. You don't need a lift, just floor jack the front of the car and crawl under there and see if the tab is still there, if not then we will go to something else.



January, 2, 2009 AT 10:24 AM

I have had the same problem with my 1986 BMW 528e.
It turned out to be a fuse not making good contact.
Looking at the fuse block from the front of the car it should be the lower left corner fuse. A 15A red bullet fuse. Hope this helped.



June, 6, 2012 AT 4:29 AM

Dr Hagerty, you are absolutely right. The only problem I have is that I don't know what the piece that I need to weld on looks like. Can you post a pic or describe it better? Thanks.


Dr. Hagerty

October, 23, 2012 AT 7:29 PM

The tab is non specific and most any compatible metal for welding should work. A 6mm bolt had worked for me in the past.

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