325 convertion, wont spark, HELP!

Post Sun Sep 21, 2008 11:46 am

So,... Iv exchanged a fcukd 325 engine for an older one (pre facelift). The starter turns everything fine but theres no spark from the plugs. The coil isnt getting power when the ignition is turned on.

Could it be...
1. Crank sensor? The older engine uses a flat crank surface with a hole in one point. The newer engine that iv just removed from the car has a missing tooth. Iv tried changing the sensors.

2. ECU not compatible or fried? (still using the original one from the removed engine) The engine iv just put in uses two ECUs. Will I need to swap the looms? Please say no!

Thanks in advance!!!!

Post Sun Sep 21, 2008 12:19 pm

I will be eventually using the megasquirt and wasted spark system that iv bought a while ago. should I go down that route? I was hoping to get the engine running stock first tho to see if it was ok

Post Sun Sep 21, 2008 2:01 pm

Does placing a wire from battery pos to terminal 15 on the coil do anything?

Post Mon Sep 22, 2008 12:03 am

If you're not getting power to the coil, it's a simple wiring fault - nothing to do with the engine at all. The green wire at the ignition switch that becomes live when you switch it on is the same green wire that connects to the coil + terminal. It goes through three plugs and sockets to get there, and possibly also an immobiliser.
What daimlerman says bypasses the lot.

Post Mon Sep 22, 2008 11:36 am

Just trying you methods Brian, if the OP now gets a spark the problem is isolated.If he does not,where next?

Post Mon Sep 22, 2008 1:41 pm

Thanks boys.
I tried jumping from the battery terminal to the positive on the coil, still nothing. Think it fried a relay while doing so which has been replaced. The coil gets power now after replacing a few relays but still no joy.

Think the next step is to rip out the wiring loom from the donor and test connect it using its ECU (of which there are two). I thought this would be an easy build! I bet its all down to one cable.

Post Mon Sep 22, 2008 1:45 pm

Connecting battery + direct to the coil + terminal (good idea to include a 15A fuse) will do one of three things:
1) The car will still turn over on the key, but still not start, in spite of power now definitely getting to the coil.
2) The car will start and run.
3) There will be a big spark and the 15A fuse will blow.
Depending on which of these happens, I will devise further tests for the OP to perform. The results of these will lead to further tests, and eventually lead to the fault.

Post Tue Sep 23, 2008 6:57 pm

Thanks again!!!! I dread the thought of paying a BMW engineer 100s to plug a cable in. Im grateful for your help.

We tried the direct connection, positive battery terminal to terminal 15 on the coil; big spark and a relay went (not sure which one). Now wev changed over a few more relays and now were getting power to the coil but still no spark. Im really not wanting to change the loom as the mega squirt I bought has been grafted into the newer e30 ECU box.

So now what?....

Post Tue Sep 23, 2008 7:01 pm

i have this conversion on a facelift car... i take it you are using the facelift loom? if you are then you will need a facelift 325 ecu.. also have you changed the position of the crank position sensor??? you have to swap the toothed pulley from the facelift engine to the pre facelift engine to accomodate the crank position sensor. ask munky what happens if this is not done....

Post Tue Sep 23, 2008 9:33 pm

Ah, i thought this might be an issue. Missing tooth vs little hole.

So to get the prefacelift engine to work using the postfacelift ECU and loom;

\ the ECU expects to read a missing tooth crank
\ so swap over the crank disk

am I right?

Post Tue Sep 23, 2008 10:32 pm

You really should try to use the post facelift engine loom and ECU, complete with the later crank position sensor and the toothed crank wheel. Not that difficult to change over, even if the engine is in the car. Only other part you might need to change over is the oil pressure switch, because of a different kind of connector.

Post Tue Sep 23, 2008 10:50 pm

yeah, keeping the post loom is essential now that I have the megasquirt to suit. My worries are lifting!! I let you know how it goes. Hopefully tomorrow night will see success. Using this 325 engine is really just a temp thing until i rebuild the 2.7. The rear mount turbo is still hanging on the back waiting to booooooost an engine. My 316i is holding me up till at this is fixed so at least im not without an e30