Ignition issues M20

[Rhyse30]

Hi all.

Wondering if anyone could help?
Car has been garaged for some time as I’ve been working on rust repairs etc… now time to get it started again but I’m not getting a spark.

When attaching a test bulb between pin 15 on the coil and an earth, the bulb lights up with the ignition on. When cranking, the bulb is on but only just, very very faint glow in the bulb wire.

Is this normal? If not what could be the cause? If it is normal, what else could cause no spark from the coil?

I’ve tested a HT lead directly to the coil and I sometimes get a faint spark when I turn on the ignition, but nothing when cranking. I’m getting fuel to the rail, unsure if injectors are pulsing.

No issues before I started working on the car.

Thanks!

[Speedtouch]

What model/year is it?
The Wiki guide may be of some use:
https://www.e30zone.net/e30wiki/index.p ... e=Ignition

[Rhyse30]

Thanks, will have a read through that.

It’s a 1989 320i with a swapped b25 in there. It does have an imobilizer (unsure if it was factory) but the wires are very difficult to trace as they’re weaved in with the loom. So that might be causing some issues as I’ve removed the dash and may have disturbed some wires/connections…

[Speedtouch]

Any idea what year/ECU number your M20B25 is? As a first step, I would check the engine-to-body earth strap is in good condition, using a multimeter to check for good continuity.

[Rhyse30]

I've checked the engine earth strap. All fine there.

I have two ECU's. I will have to double check when I'm back in my workshop later this week but I believe I have a 0261 200 172 from the b20 original engine, and I have a 0261 200 380 that came with the b25 engine. This has your mild chip that I installed a while back and was working fine with the car when it was running a few years ago.

As mentioned, when I have the 12v 5w test bulb on the coil, it lights up with ignition on, but it pretty much goes out when the engine is cranking. Shouldn't the light stay on when I crank the engine?

Thanks again!

[Speedtouch]

I wouldn't have thought so, if it's on the switched side of the coil because the power is being pulsed to it (assuming the CPS is working), hence causing the dimming, as the bulb is effectively being switched on and off rapidly.

I would use a multimeter to test the resistance of the HT leads - they should read around 10 kilohms or so, then hold a spark plug against the rocker cover and check for a spark, repeating his for all cylinders.

[Rhyse30]

Ok thanks. Will try this again with all HT leads when I’m back with the car.

I did test one plug resting on the rocket cover but only had a tiny spark on occasions when I turned the key ignition on. I tested a spark plug direct on the coil HT lead and had the same, weak spark when ignition on with the key, but no spark when cranking the engine.

[Speedtouch]

You could always try swapping the ECU temporarily with the 172 one, to test for a spark if the other one doesn't seem to work; they are essentially identical, aside from the program on the EPROM chip. So, if you get a good spark with that, you could swap the chip into it.

[Rhyse30]

Thanks SpeedTouch!

I’ve tested with both ECUs and still getting exactly the same results, no spark from HT leads on distributor, or HT lead directly on the coil. I’ve tried to test the DME relay by bridging both 87 pins and 30 and made no difference. Might need to test that properly again? But it makes me think it’s a wuring issue between the ECU and anything else along the chain to the coil?

Might be worth mentioning, the only other major change to power/wiring is that I’ve relocated the battery to the boot using an E36 cable and E36 terminal connector in the engine bay. Would any change here cause anything like this?

Thanks!

[Speedtouch]

I once had a problem with a 535i that failed to start, because one of the fusible links had blown in the battery lead in the boot, so it's worth checking to see if you're getting a decent switched +12V at the relevant ECU terminal(s).

I ran a temporary lead to the ECU or DME relay (can't remember which) and it fired up again.

[Rhyse30]

Coming back to this now I’ve had a bit more time in the garage. Here’s where I am so far:

Just for for info, car interior has been stripped, so nothing much inside except the wiring, cluster and ECU plugged in. It does have an immobilizer, don’t believe it’s factory but it’s wired in pretty well and difficult to trace. Unsure how exactly it’s wired but the green wire loop connection is still in it’s plug by the accessories sockets.

Engine cranks but doesn’t fire.
DME relay looks to be working.
Fuel pump relay working
Fuel pump running when cracking and seeing fuel at the rail.
Unsure if injectors are working when cranking.
When cranking with fuel pump fuse in, pulled plugs and they are dry.
No spark at the plugs.
No spark when pluging one directly to coil king pin.
Coil resinstance in spec.
HT resistance in spec.
Tested CPS as best as possible with multimeter, all number within spec.
Resistance pretty much the same between pins 47 and 48 on the ECU plug.
5w test light on when connected between ignition coil pin 15 and a good earth.
Test light goes off when cranking the engine.
Continuity between coil earth lead terminal and ECU plug pin 1.
Supplied the coil with power direct from the battery, test lamp now stays on when cranking but still no spark direct fron king pin.
Tested another coil with same results.
Moved battery to the boot using an E36 cable and engine bay terminal, fuseable link is fine.
Have tested two ECU’s, a 173 and a 172. The 172 has your Speedtouch mild chip.

Maybe worth noting, when ignition is on I get lights on the cluster like battery, oil, and the red fuel empty light (fuel gauge does show a bit of fuel as I put some in), all these lights go out when cranking, even the fuel empty loght. Unsure if that’s related to the bulb on the coil also going out when cranking, like there’s certain things not getting power when cranking.

All was working fine but the rust repairs (reason why i took it off the road in the first place) took a bit longer so it hasn’t run in a few years. Was running fine before so it must be something I’ve dinconnected/disturbed, or just something failing after sitting for so long.

Any suggestions would be more than welcome as I’m running out of ideas. Apologies for the long post, just wanted to get all details in.

Thanks!!

[Speedtouch]

The non-starting issue would appear to be down to not getting any spark. I would double-check that the ECU is being powered when the ignition is on, and that engine-to-body earths are all good.

Not sure that "Supplied the coil with power direct from the battery, test lamp now stays on when cranking but still no spark direct from king pin." was a good idea - you could have fried the ECU's output transistors!

It could be down to the immobiliser - did you have the key to operate that before taking it off the road?

[Rhyse30]

I did also question giving the coil direct power from the battery, but this was advice I received. If it helped, I removed the postive wire first so it was only a direct 12v to pin 15 on the coil that was connected, and the ground to the ECU. Wouldn’t this just be similar to the 12v supply the coil is getting from the loom anyway?

What’s the best way to check if the ECU is getting power when cranking?

Yeah it’s always had the immobilizer, and never had issues with it before. I have the fob to work it and still have to use it to enable the engine to crank.

Thanks

[Speedtouch]

Try the checks mentioned in this guide:
https://www.e30zone.net/e30wiki/index.php?title=DME

[Rhyse30]

Thanks for all the help SpeedTouch.

I'm now stuck as I've tried everything I can think of.

I've completely disconnected the Thacham immobilizer so everything is back to factory and this didn't make a difference. DME relay tests all fine, Fuel pump working. Engine cranks. As for as I can tell I have the correct voltages at the ECU at the correct pins with ignition off / ignition on. I will double check these. The one thing I'm not 100% on is if I'm getting earth at the correct pins on the ECU but will go back with fresh eyes to check this.

The issue I've still got is that I'm getting no spark, and I don't think my injectors are firing (spark plugs dry after cranking with fuel pump on).

Not sure if relevant but the one thing that doesn't seem right to me is with ignition on I get 12v at the coil. When cranking I loose power to the coil. Could this be the ECU not grounding something or just I happen to have two faulty ECU's? the fact that my test bulb on the coil goes out when cranking doesn't make sense to me.

I will keep digging, and thanks again for all the help!

[Speedtouch]

I would suggest trying a different CPS, since this is the usual cause of non-start issues - maybe you could borrow one from a nearby Zoner?

Also, I don't know if you have the E30 Haynes manual, but the E30 Wiki has some wiring diagrams which may be of use:
https://www.e30zone.net/e30wiki/index.p ... g_Diagrams

[Rhyse30]

Yeah I think that’ll be my next step with the CPS.

Yeah the Haynes Manual has had a lot of use recently.

Thanks for the link! Gone through the diagrams and everything seems correct.

Thanks again!

[Speedtouch]

No problem. I would also check this connector to the injectors:
https://www.e30zone.net/e30wiki/index.php?title=C191

Perhaps also try some Eze-Start/Start Ya Bastard or similar starting fluid down the throttle body to see if you get any sign of life (once you get a spark, of course...)

[Rhyse30]

Hi!

Just spent a bit more time on the car.

I’ve installed a known working CPS.
Tested DME relay.

Still no difference. What I did find which I don’t think is right is with the ignition switch. With the wires on tye ignition switch, I’m getting the below:

Red wire
Ignition off - 12v (ish)
Ignition on - 12v (ish)
Cranking - slightly less than 12v

Green wire
Ignition off - 0v
Ignition on - 12v (ish)
Cranking - 0-3v

Black/yellow
Ignition off - nothing
Igniition on - nothing
Cranking - 12v (ish) which makes sense as the engine is cranking.

With the battery disconnected I checked continuity between the red wire going into the ignition switch, and the green coming out… No continuity between the two with ignition off, continuity with ignition on, then no continuity when key in cranking position.

Surely I should be getting around 12v at the green wire when cranking that then powers the ECU, ignition coil, and a few other things I can’t remember? So could this be a faulty ignition switch?

Unsure if this a fixable parts or any other tests I could do? Or just what I’ve tested shows it’s not working?

Just to recap, starter works, engine cranks, fuel going to the rail when cranking, no spark, no power at coil when cranking, plugs dry after cranking so no injectors?

Thanks again

[Speedtouch]

I would have thought it may well be suspect. Perhaps you could try hooking a direct 12V connection to the the relevant ECU pin(s), then have a go at starting it...

[Rhyse30]

Thank you so much for all your help Speedtouch!

Early start this morning (for me and the car )!

Suspecting the ignition switch, turned the ignition on, jumped pin 11 and 14 on the C101 plug to engage the starter, and it fired straight up!!

So green wire not getting power with the key in position 3. So it engaged the starter, but no power to the ECU/Coil etc…

Can finally start putting the car back together now!

Thanks again for all your help mate, really appreciate it!

[Speedtouch]

Great stuff, and glad to be of help. The ignition switch itself may not be at fault; have you traced this green wire where it goes behind the dashboard, as this can be a common issue?

https://www.e30zone.net/e30wiki/index.p ... Green_Wire

Also, it could be worth lubricating the ignition lock with graphite penetrating oil or similar, and working it back and forth several times.

[Rhyse30]

Hey Speedtouch.

Yeah I’ve traced the green wire all the way back to the ignition switch. Doesn’t show any breaks in the wire. I’ve now opened the ignition switch and cleaned the contacts and all is now working fine!
Finally!
Thanks

[Speedtouch]

Good to hear that, fella.