b25 swap. no spark.

[gasgasrob]

hi there,

just performed he b25 swap into my e30 and have no spark at all. The coil leads show a voltage of 12v which is fine but when connected to a coil (I have 3 to try) there is no spark to any plug.

The voltage drops to 0v when the leads are connected to the coil (voltmeter on terminal posts)

CPS shows a good resistance.

Any help?

thanks

[Grrrmachine]

Don't use a meter to confirm voltage, you'll get false readings. Use a bulb.

First check if you're getting fuel. If it's a CPS/DME related issue, you'll lose both fuel and spark at the same time. If you have fuel, then the issue is ignition related and relatively simple.

There's a good troubleshooter in the Wiki for exactly this situation:

http://www.e30zone.net/e30zonewiki/inde ... oubleshoot

but my money is that you've got the CPS plugged into the wrong socket on the loom.

[gasgasrob]

haha ive plugged the cps into both sockets! it made no difference. I dont think its getting fuel either but will confirm that later on today.

Ive tried two ecus so that surely rules out an ecu fault. Leads are the only part of the ignition circuit that havent been changed.

[Speedtouch]

As above, use a 12V test lamp to confirm you're getting power to the coil.

Also check the engine-to-body earth strap is securely fitted.

[gasgasrob]

changed coil, changed cps, changed ecu. The body to earth strap looks secure and is tight. the starter works fine so I assumed the strap was fine!

[Speedtouch]

Yes, if the starter works fine then it probably is OK.

Have you checked the notorious green wire that runs behind the glovebox?

[gasgasrob]

I havent checked that no but this could the cause of the problem!

How is best to check it?

Thanks for all your help so far once again

[gasgasrob]

I have just checked for continuity between pin 15 and 7 and there is none. Can this only mean a break in the loom somewhere?

[Grrrmachine]

Do you mean pin 15 of the coil and pin 7 of the C101? Try and be clear, otherwise things get very confusing very quickly. If so, and you're not getting continuity, then there probably is a break as the engine loom is a one-piece unit for the most part. Did the engine loom come with the replacement engine, or is it the original one for the car?

Like I said, be sure you're getting fuel before chasing this too far, otherwise you're barking up the wrong tree. But if you're sure you're getting fuel, you can run a bridge wire from the battery to the coil pin 15, which will make the entire ignition live so that you can check the engine fires up.

[gasgasrob]

its the orign\l loom for the car, the old engine did not start after i moved the loom over to change injectors. Also, I know the engine oil sensor wires have been burnt out which could of melted others and caused a short somewhere?

[Grrrmachine]

The plot thickens

Yes, if the oil sensor wire burned out then significant damage could have been done elsewhere, including the vehicle loom. This is caused by corrosion on the engine/body earth strap, causing power to short through the oil sensor wire instead.

Considering the cost, it may make more sense to get hold of a replacement M20 loom.

[gasgasrob]

where is best to look for one dude?

[Grrrmachine]

Stick a Wanted ad on here. Plenty of people fragging these cars for spares, and the loom from a 320i will work fine.

Presuming the engine is from a post-1987 car, you'll want a loom that's also 1988 or newer (Motronic 1.3).

[gasgasrob]

would it be worth stripping the sheath back and tracing any breaks or problems?

[Grrrmachine]

you can do that, if you have the patience and want to save the money. Like I said, bridge a wire from the battery to the coil to confirm that this is in fact the problem, otherwise you're buying parts for no purpose (like you already have done).

Methodical testing is worth much more than blind guessing. You still haven't confirmed fuel yet, so anything else I say is purely guesswork at this point.

[Brianmoooore]

Do you mean pin 15 of the coil and pin 7 of the C101? Try and be clear, otherwise things get very confusing very quickly. If so, and you're not getting continuity, then there probably is a break as the engine loom is a one-piece unit for the most part.

Red 325 touring in my sig. had a dealer fitted immobiliser neatly spliced into the loom branch to the coil, instead of using the plug behind the glovebox, so there's at least one loom that doesn't have continuity between 15 and 7.

[gasgasrob]

just got a new loom, as the old one was burnt out etc. Ive noticed that there is a large square plug next to the ecu plug coming off, which is different to the original!

Also I think the tps has a round female plug on it instead of square. Is that simply a case of rewiring?

Thanks

[Grrrmachine]

Christ, sounds like you've bought the loom off an automatic, and possibly even a pre-facelift one at that. Are you sure it's got the correct 55-pin plug for the ECU?

[gasgasrob]

yep its the same ecu plug.

[gasgasrob]

Im assuming the larger plug that splits off near the ecu plug is for the auto box/controls etc but my main concern is the tps plug!

[Grrrmachine]

Two solutions then. Fit the automatic TPS, or cut the loom and fit the plug for the manual TPS by joining the same wire colours together.

[gasgasrob]

right Im at my wits end with all this now. New loom and still no spark. tried jumping pin 15 of the coil to the battery and still nothing. I dont think the ecu is even trying to pulse the coil!

Any help please losing faith in the e30 now

[Brianmoooore]

As Grrrmachine has already asked three times, are you sure the fuel pump runs when you crank the engine?

[gasgasrob]

Sorry, no I dont think it does, surely showing that either the DME is not getting power or not picking up a reading from the CPS?

[gasgasrob]

tried grounding pin 30 to body, no power at 87-87