628csi Igntion system queries

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Caff
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628csi Igntion system queries

Post by Caff »

Hello all!
Been having some problems with my ignition system on a UK spec 1984 628 csi manual.
So far if ascertained that on key turn I'm getting 12v at the coil on terminal 15. The resistance on the coil is 1.5 between the two poles and then 7.5k between +ve and the HT out. When tested on crank, it turns over a peach on the key (new starter was fitted a short while ago), stinks of fuel and there is no spark.
Now I'm rather confident that it is the coil in all of this as before I took the car off the road to refurb it i did the valve lash and it also wouldn't start then, tested for spark and it was weak. I waited a bit with the plugs out as i didn't want to risk flooding it and then it started once the plugs had dried and I left it that and did a bunch of miles (easily 2500) and it was running pretty rich for the duration.
I'm wondering if any one has extra info on the ignition system for the 2.8 just in-case it turns out not to be the coil in the end, I have looked for crank rotation/speed sensors to clean and have found absolutely none. But then again its on proper crank driven distributor so cant see why it would have them anyway. It appears to have a vaccuum advance system also.

The 2.8s are getting very thin on the ground now in the UK so have been struggling to find any information.

Thanks in advance for any help/drawings provided
plip1953
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Re: 628csi Igntion system queries

Post by plip1953 »

I think it might be advisable to also look at the distributor cap and in particular the rotor arm. Although I've not personally encountered any issues, I've read many times that these items are very sensitive to being in good condition, and that even brand new aftermarket versions are pretty much a waste of space.
Phil
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Caff
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Re: 628csi Igntion system queries

Post by Caff »

forgot to mention that when i bought it i fitted leads, cap and rotor arm, it was at the time my only car so i changed a bunch of stuff so i knew i could trust it haha!
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Caff
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Re: 628csi Igntion system queries

Post by Caff »

](*,)

And of course it's not the coil.

So I have looked for the two sensors on the bell housing that I've seen people talk about on other threads but they straight up are not there. The two spots they're supposed to fit in are smooth and dont appear to exist.

I'm getting 11.6v at the hot side of the coil with the ignition on.
The coil has been changed for a known good one, the cap is new, rotor and leads.
So I start working back in my memory and before the car was stripped to be painted we tried to fire it and it was flat. And my friend hooked up the jumper kit and put the leads on backwards. Wondering if this has cooked anything???


I was checking the ignition wiring and tracked it to a box and some little solid state thing mounted on a heatsink on the inside of the right hand wing. Googled the part numbers and they're both related to ignition too. Before I replace parts willy nilly is there any electeical testing I can do to these items and any other parts of the car?


Also. Is a 590cca battery enough? Wondering if the battery doesnt have the knackers to crank and give the coil enough juice to get spark? Its borrowed from a series 2 land rover as my brand new battery (for the car) was stolen in a previous workspace :twisted:
Pod
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Re: 628csi Igntion system queries

Post by Pod »

I would have thought the battery should be fine to start the car. I’ll be dismantling a 628 CSiA shortly, so if you need any parts, give me a shout.
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Caff
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Re: 628csi Igntion system queries

Post by Caff »

Pod wrote: Wed Jan 08, 2020 2:29 am I would have thought the battery should be fine to start the car. I’ll be dismantling a 628 CSiA shortly, so if you need any parts, give me a shout.
Are you from the uk?
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Re: 628csi Igntion system queries

Post by Pod »

Caff wrote: Wed Jan 08, 2020 8:25 am
Pod wrote: Wed Jan 08, 2020 2:29 am I would have thought the battery should be fine to start the car. I’ll be dismantling a 628 CSiA shortly, so if you need any parts, give me a shout.
Are you from the uk?
Absolutely😉
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Brucey
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Re: 628csi Igntion system queries

Post by Brucey »

628 CSI runs LE-Jetronic. Most of the info you will find in relation to E24 relates to Motronic in its various guises, and whilst some parts are similar (like the cold start injector function using a thermotime switch), you'll get nowhere fast if you try and use motronic as a guide.

In relation to your car a reverse polarity on the battery could have shagged anything and/or everything, so you are in the realms of 'parts change bingo'. The first thing to do is check to see that you have spark or not on cranking, and to fix that first.

There's only one crank sensor on a 628CSi and that is at the front. Its sole function is to talk to the BMW service computer; it plays no part in running the car. The whole engine management system uses the distributor as the primary timing source; the green wire carries the signal into the ignition system (LE-jet uses mapped ignition in the larger of the two boxes on the inner wing) and the box sends out two main signals; one to the ignition amplifier (the second smaller box on the inner wing) which drives the coil and another to the fuel injection ECU.

The whole lot is powered from the 'combination relay' (including the fuel pump). These relays often fail and trying a spare one is a good first step. The fuel system is primed (by the pump running for a few seconds) when the ignition is first switched on. You should hear the pump run and then stop.

If you have spark during cranking and a working cold start injector system (thermotime switch, fuel pressure and cold start injector that opens), then the engine should fire on cranking even if the rest of the fuel injection systems is kaput. If the main injectors are not working the engine will quit after a second or two once the key is in 'run' not 'crank'.

So

1) check for spark
2) check for priming of the fuel system
3) check for cold start injector function

and then report back.

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Caff
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Re: 628csi Igntion system queries

Post by Caff »

Thanks Brucey!

Yeah I have no spark at all.
It stinks if fuel but doesnt flood when cranking for a long time. Llugs are wet when removed after cranking also. Pretty confident that everything from coil onwards to plug is fine. Could the sensor in the dizzy need a clean?
Fuel pump is also priming

After that its replace the two ignition boxes and some relays I presume? Then the ecu if that doesnt work?
Electrically I know that the power windows work, wipers, central locking, the instrument binaccle and the fault finding thing works. Dont have headlights or tail lights hooked up yet.
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Brucey
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Re: 628csi Igntion system queries

Post by Brucey »

the fuel injection ECU has precious little to do with the ignition system, so that would be the last thing I'd look at. That you have wet plugs and fuel smell may just mean that the cold start system is working (BTW when cranking it doesn't carry on spraying fuel indefinitely, that is what the thermotime switch is for).

For the system to work you of course need +12V on the coil, and if you don't have that you won't have spark. So check that out.

If you have an oscilloscope you can check the output from the hall effect sensor in the distributor too. Past that it is getting on for parts change bingo time.

cheers
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Caff
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Re: 628csi Igntion system queries

Post by Caff »

Brucey wrote: Thu Jan 09, 2020 11:39 am the fuel injection ECU has precious little to do with the ignition system, so that would be the last thing I'd look at. That you have wet plugs and fuel smell may just mean that the cold start system is working (BTW when cranking it doesn't carry on spraying fuel indefinitely, that is what the thermotime switch is for).

For the system to work you of course need +12V on the coil, and if you don't have that you won't have spark. So check that out.

If you have an oscilloscope you can check the output from the hall effect sensor in the distributor too. Past that it is getting on for parts change bingo time.

cheers
Yeah coil is getting 11.6v at t15 with the ignition switch on.

Ahh, no osmelloscope so looks like its bingo. My spare engine might have that sensor on though so might try swapping that first.
After that let's play bingo! \:D/
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Caff
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Re: 628csi Igntion system queries

Post by Caff »

Fitted a replacement ignition box and it fired immediately. Happy days! So it was part No
BOSCH 0-227-920 001
That had failed, pretty sure having the battery backwards must have killed the microchip inside. Luckily my ecu appears to be fine as it starts and revs like a champ.
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