no spark m20...

[e30slut]

hey I just dropped in a b25 for a 1989 525i and I get no spark. The engine is ground correctly i just dont have spark coming from the ignition coil.

What would keep the ignition coil from firing? Also I dont think I have my altenator hooked up, could that keep her from sparking?

the oil pressure switch wire has broken, Could that be it?

[SpecM]

getting 12v from DME?

[e30slut]

dme? whats that?

If thats the cpu then I dont know how to check voltage.

Now the coolant light and the engine oil light is on... Could that keep the coil from sparking?

[smoke4ndmears]

oil pressure/level and coolant lights will not affect it. the dme is the engine management computer, and could be the source of your issues, as well as a bad coil, improperly routed ignition cables, etc etc. keep searching the forum and use your manual to try to understand how the system works.

[SpecM]

If thats the cpu then I dont know how to check voltage.

then how do you know its not getting spark?
and how can you expect to diag anything if you can't use a voltmeter?

*sigh*

make sure the CPS is connected and not damaged. that's what the DME (no, its not a cpu) needs to see to turn on the coil.

[e30slut]

okay. I got the cps and swapped it out.. same issue...

Now the ecm is making a low buzzing noise...

All the ignition wiring is correct.

I checked for spark by removing the coil plug and holding it next to a ground. Usually when I take the cable out the coil you can see it spark as well... Also added starting fluid and no boom.... All wires are correct.

[e30slut]

also...
Thanks for your help...

[SpecM]

maybe the coil is bad

[jlevie]

Make sure that you didn't swap the cylinder ID and CPS connectors.

[e30slut]

Make sure that you didn't swap the cylinder ID and CPS connectors.

cylinder id? whats that? also should i swap the cps?!

[jlevie]

An M20B25 engine has two timing inputs to the DME. One is the CPS signal and the other is the cylinder ID signal from a pulse transformer on an ignition wire. The two connectors are identical and located next to each other. So it is pretty easy to swap them. If they are swapped the DME won't get timing reference data and won't fire the coil or injectors.

[e30slut]

oh, that wire thats hooked to the #6 ignition wire? okay let me reverse them and see if thats was it...... Is there any other cables I might have crossed that you might know about?

[smoke4ndmears]

i think he means another set. my 84 has the two located at the aft end of the engine as two square-ish plugs, one black one grey.

[e30slut]

The plugs are in correctly... I'm hopefully going to be getting a new ecu and see if thats the culprit...

[e30slut]

swapped the ECU and still no spark. Nothing. Not even a put.
Mind you this is the m20 from the 525.

What could I be missing?