M50 Did i mess up my ecu?

[tgrandahl]

Ok so over the past month i have been been painting / rebuilding my 525i while my transportation needs are still low. I changed the color from gold to ruby red so there wasnt an option as to what i could get away with not painting.

So anyways i stripped everything out of the engine bay except the engine as the m50 is small enough i could paint around it fine with the exhause manifold gone. This includes the bcm, ecu, and everything else in that enclosure. Now that i have everything back togeather i go to start it and it cranks and only gives a very faint sign of possibly wanting to start. Fair enough, it has been sitting for about a month now, so i give it a second try and have the same result but this time it sounds like it has a better chance of starting.

It sounds almost like everything is just spinning and there is no compression, i checked all the connections that i had disconnected and try again. Still no luck but by the fifth try it actually did start but quickly stalled, so i tried it again and gave it a little gas it ran a bit longer and was very very rough and then died.

Now the only thing that i did to the engine was replace the thermostat and of course all the coolant was drained. So i cant think of anything else but the ecu, but then again i really wouldnt know what to check. When it does run it smokes a little too. Im really not even sure where to start here, so any surrestions would be greatly appreciated.

Thanks,
Tyler

[joshua43214]

Treat it like any other no start, start with the basics. Do you have spark? Do you have fuel? check both.

Any chance some paint got in some connectors or into a fuel line?

[Rustam]

Ok so over the past month i have been been painting / rebuilding my 525i while my transportation needs are still low. I changed the color from gold to ruby red so there wasnt an option as to what i could get away with not painting.

So anyways i stripped everything out of the engine bay except the engine as the m50 is small enough i could paint around it fine with the exhause manifold gone. This includes the bcm, ecu, and everything else in that enclosure. Now that i have everything back togeather i go to start it and it cranks and only gives a very faint sign of possibly wanting to start. Fair enough, it has been sitting for about a month now, so i give it a second try and have the same result but this time it sounds like it has a better chance of starting.

It sounds almost like everything is just spinning and there is no compression, i checked all the connections that i had disconnected and try again. Still no luck but by the fifth try it actually did start but quickly stalled, so i tried it again and gave it a little gas it ran a bit longer and was very very rough and then died.

Now the only thing that i did to the engine was replace the thermostat and of course all the coolant was drained. So i cant think of anything else but the ecu, but then again i really wouldnt know what to check. When it does run it smokes a little too. Im really not even sure where to start here, so any surrestions would be greatly appreciated.

Thanks,
Tyler

crakshaft position sensor - where is it and how is it?

[tgrandahl]

Treat it like any other no start, start with the basics. Do you have spark? Do you have fuel? check both.

Any chance some paint got in some connectors or into a fuel line?

Fuel pressure is there and i dont think there is any way paint got in any part of the engine as every bit was well masked and covered and sealed again twice. I also doubt there is anything in the fuel line because it was never removed. I cant really suspect its the spark because it is almost starting and all my coil packs + plugs were replaced about 4 months ago.

[ArtemLepilov]

Check all the connections on all the sensors and spark plug coils and check that the fuel injector connectors are all connected to the injectors. ECU may get messed up if somsthing is not connected right but make sure about all the other connections first. It happened to me the first time and i did screw up my ECU.

PS - is anything i have a spare #405 ECU in the worst case I can give you that.

-Artem

[tgrandahl]

crakshaft position sensor - where is it and how is it?

It looks to be right where it supposed to be and just a little dirty. I dont remember disconnecting this but i suppose i can try to check. I would have to take off the intake manifold to get to the wiring right?

[Blitzkrieg Bob]

you may have painted the connection to the body.

[tgrandahl]

Check all the connections on all the sensors and spark plug coils and check that the fuel injector connectors are all connected to the injectors. ECU may get messed up if somsthing is not connected right but make sure about all the other connections first. It happened to me the first time and i did screw up my ECU.

PS - is anything i have a spare #405 ECU in the worst case I can give you that.

-Artem

thanks artem, ill go look over / reseat all connections.

[Rustam]

It looks to be right where it supposed to be and just a little dirty. I dont remember disconnecting this but i suppose i can try to check. I would have to take off the intake manifold to get to the wiring right?

I don't know.
I only meant to draw your attention to this part since it can be responsible for "no start" condition...

[tgrandahl]

you may have painted the connection to the body.

You got it, when i checked all the connections again today the ground by the ecu / bcm enclosure was reading a couple hundred ohms or resistance. Its running fine again and i am quite relieved. Thanks everyone