No crank, no start 88' 325 w/ m50b25nv

[1987_325is]

This is my first e30 swap. Go ahead and knock me because its only an m50 but I thought it would be cool and it was cheap. I am having a problem with wiring. I cant get it to crank at all and fuel pump won't turn on. Basically no motor activity. After going over the e30 24v wiki page and loom charts. I am pretty sure that I have got the c101 connector and x20 connector wired correctly. I am using an e34 harness and 405 green label ecu that came with the motor. When key is turned I will get activity in the overhead check board so it is not a problem with the red ignition wire from the fuse box.

Ideas:
I did not hook up the oil pressure switch ground to the harness. Could this cause it? It should still crank right?

I read on the wiki page that no engine activity could be solved underneath the dash. There are supposed to be two green wires and black and yellow wires. Quoted below for reference. I cannot find these wires and have the glovebox out. I have one green wire which is not plain and normally goes to the ecu side of the m20 harness. Is this one of the wires? And if so where should it connect on the m50 harness?

"Not Starting

If NOTHING happens when you turn the key, then you have an issue with the red wire that feeds the ignition switch from the fuse box.


If nothing engine-related happens when you turn the key, then the issue is with the plain green wires that drive the ignition. These wires are found behind the glovebox, where you will probably find a pair not connected to anything; these need to be joined together.


In the same area as these green wires, you should find two single plug and sockets, each joining a black/yellow wire to another wire (plain black, usually). Disconnect both of these and plug the two halves with black/yellow wires together.


This bypasses the auto inhibitor switch, and arranges the wiring just as it would be from the factory on a manual car. Follow the two left over wires to a relay, remove the relay base, the wires, and the other wires to the relay, which you will find a lead to the area under the front console where your gear lever will be. You need to find the reverse light loom and gear lever grommet from a manual E30, which will connect between the reverse light switch on the gearbox and the plug you have found."

http://84.45.115.78/e30zonewiki/index.php/M5x_Looms

Sorry for the disorganization. I just had a lot of ideas going through my head. Thanks in advance.

[1987_325is]

Anyone? Help me give this project some new wind!

[EtaSport]

Need to check all powers and grounds. Also, battery good?

Check the 3 relays on the engine harness for power. Main relay is hot at all times on the red wire, if you have no power there you missed something. Key on you should have power at the red/white wires, if not you have a bad main relay or a problem with your ignition switch wiring.

Make sure your engine ground is good, make sure your connections on starter and alternator are tight and properly connected to the battery. You can always check for power at the black/yellow wire on the starter as well.

[1987_325is]

Damn, seems so simple when you put it that way, thanks man! I am going to check for power at the main relay and other relays tomorrow. I was literally thinking today that I should check for power at the fuel pump to see if the wiring was right because I would not hear the pump prime with the key was in the on position. By checking at the relays it would cover power to the pump too, cool. Thanks!

[EtaSport]

You just need to think simple with these things, over-thinking gets you in trouble. If you look at wiring diagrams to see how things work it will make a lot more sense make makes troubleshooting a breeze. That was all from the top of my head, granted I do work on bmw electrical problems just about every day lol.

[1987_325is]

All of my grounds were good, I had power to the starter and ecu. No power to the main relays whatsoever. So I have a problem with my wiring. I would go through all the etks and what not but I just don't have the time between summer classes and work all day. Is there a trust worthy guide to follow? Like Rmeuropean?

[EtaSport]

The red wire to the main relay should be connected to the battery cable somewhere. It sounds like it could have been missed. You can always jump that solid red wire to 12v and verify everything else. First rule to remember all solid reds are hot at all times, reds with white stripes are key on hot. That will get you pretty far.

You might have to pull some wire coverings off to verify colors, pay particular attention to those by the DME plug, I missed a power wire on my first swap that gave me the same issue you are describing.

[1987_325is]

I see, is it common that most people have to hook that wire up to a power somewhere? I.E. jumping it or tracing it to the end and hooking it up to a hot wire.

[EtaSport]

It can be, it usually comes down to something simple in a no crank situation. You've only got a few things that it can be, eliminating them 1 by 1 is the easiest way to do so. I'm sure that you can figure this out, just keep at it.

Took me almost 2 weeks going back and forth on my buddies m50 swap, first we ever did, to find the keyway broken off the crank trigger gear which threw the timing completely off.

[phillye30fanboy]

This wire?

[EtaSport]

That wire needs to be connected to B+ if its red its 12 volts, if its brown send it to ground! Be cautious cause most of the wires on the m50 wiring harness have a black covering over them.

[NickL]

^^^ check your b+ wiring. The wires have black insulation so you could of easily mixed up a power and ground. Is the check engine light on in the dash when the key is turned?