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resolder ECU? (archive)
[ Follow Ups ] [ 5-series (E28) Message Board ] [ Msg. Board FAQ ]
Posted by richard on January 29, 2001 at 11:36:01:

In Reply to: 87 535is No Start posted by Charlie on January 28, 2001 at 21:18:29:

Charlie,

If your coil voltage is good, I'd recommend resoldering the ECU. My car wouldn't start about a year+ ago and it turned out to be the ECU. It's a common failure and easy fix!

I got my instructions from a fellow named Ed. His instructions are below:

Good Luck!!
richard

I had the same problem on my M6 a while back. I found it to be the solder
joints around the power transistor on the ECU. If you or someone is some
what electrically inclined, you can fix it.

Remove the ECU--open the cover and open the PCB board halves. Next you need
to take off the bottom cover from the lower PCB. Be careful with the 2
screws that hold the main connector to the assembly. I stripped one-no nice.

When you have access to the bottom PCB, locate the BIG transistor--looks
like an oval flange with a round cover on it. It is mounted to a heat sink
sideways on the PCB. There will be three leads coming from the transistor
down to the PCB. These are the leads that need soldering on the copper side
of the board. This is the surface that is next to the bottom cover.

Reassemble.

Mine had a weak spark, sometime would run fine then quit almost like a fuel
issue because it would run rough, catch and go and then rough and quit. Had
me confused until I saw weak spark and then no spark. I looked at the drive
signal from the ECU and found it to be totally incorrect. I have not had any
further problem since resoldering the device. I have also fix about 2 dozen
ECUs with the same problem. Not to say that something else could be wrong
but this is my best guess.

Hope this helps! sorry I guess I sudda taken some pics of the ECU. If I get
another I'll do it for future reference.

Best Regards,

Ed


Can anybody help with a no-start? Checked relays, they're good. Checked fuel pumps, there good. Checked spark at the spark plugs, no good. Is safe to say that it's a bad coil? Or can a bad Motronics also be the cause for it to not give out spark?

Thanks,

Charlie

Any help will be greatly appreciated.




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