Ignition problem 1990 525i

[jchungmoonj]

I have a 1990 525i and it has an intermittant problem of not starting. It cranks but will not start. when this happens I do not get a spark. When it does start the car runs great. It does not die on me at all. I can't ever tell when it won't start. I have taken it to a BMW mechanic and both times when they got in to check it out the car started for them. They can not test it unless it does not start while at the shop. They think it might be an ignition switch but they can't be for sure. I have checked the comp and fuel relays, ignition coil and wire. replaced spark plugs, cap and rotor. Any suggestions? Thanks Jeff

[4-Door Flunky]

Main relay, dude. That's what my problem was. Although mine was never intermittent. Just one day, it wouldn't start.
I think my main relay was cutting off fuel to the fuel pump.
Also, these problems can come from old fuses. A fuse can look perfectly fine...and still not work.
Get a couple of new fuses, and replace the one going to the fuel pump.
If a fuse is getting a bad connection, that would explain it being intermittent, too. Check fuses!
Flunky
PS-I had this problem so many times, I just got on eBay, bought ALL of the fuses brand new for $10, and replaced them all!

[jchungmoonj]

This is an update about my 525i. Found out what the problem was. It was a bad crank angle sensor the part cost 96 dollars. If the sensor doesn't work there will be no spark. It is on the front of the engine and is held on by one bolt

[4-Door Flunky]

Wow! Thanks for the update!
(Like like my suggestion was a bunch of crap)
Flunky