M40 running issues,test bulbs fitted....

[Brianmoooore]

Brian, just thinking of the unexplained problem Murran had with his m20b25 equipped e21. Maybe some sort of grounding fault? Malcolm seems to have swapped out everything possible...??

Can't be a lot wrong with the engine block to battery neg. path if it cranks OK, without smoke and sparks, and the earthing point for the engine loom is actually between the battery neg. lead and the lead's connection to the body.
Could remove the loom earth lead from the stud on the suspension turret plate, clean it up and refit, but it's not a place known to give trouble.

[Brianmoooore]

Is there still definitely a strong spark at the plugs when it's cranked?
Does fuel definitely flow from the fuel supply pipe, if it's pulled off from the injector rail, and the engine is cranked?
A long shot I've just thought of: The crank pullies on M40 engines have been known to come adrift at the rubber bit, allowing the toothed wheel to turn relative to the crankshaft, throwing the timing a mile out.

[mhuk]

Your spark plugs are all clean. When you crank over do the plugs get wet?

[daimlerman]

No spark at all.
Shorting out the fuel pump relay to run the pump continuosly makes no difference.
If the crank pulley had moved out of place,I would still expect to get a spark.....
Engine cranks at normal speed,certain this is electrical in some way,when the problem started in the early hours of Monday morning,as soon as the engine cut,the rev. counter fell to zero,even though the engine was turning....would not expect that....then it would re-start after a short 'breather',the period it would run for got shorter and shorter,now it just will not run.
When it did run,it ran on all pots and sounded fine,quietest M40 I have ever heard!

[Brianmoooore]

You would still get a spark with a damaged crank pulley - I thought you were still getting a spark, but, from your post above, I see you aren't.
Does the fuel pump run when you crank the engine?

[daimlerman]

You would still get a spark with a damaged crank pulley - I thought you were still getting a spark, but, from your post above, I see you aren't.
Does the fuel pump run when you crank the engine?

Agree ref crank pulley!
Fuel pump is delivering fuel to the rail in huge quantities!

[Brianmoooore]

If the fuel pump runs when the engine is cranked, then the ECU is seeing and processing pulses from the crank sensor. One side of the coil is connected to 12 volts ignition live, and you have checked that is present (even when cranking?), so all that remains to produce a spark is for the ECU to momentarily earth the - side of the coil, which it does with the same pulses that engage the fuel pump.
Have you connected a spark plug directly to the king post of the ignition coil?
Does the ignition coil get hot?
Only other thing I can think of is to thoroughly check over the condition of the buckets in the ECU plug, and to check that 12 volts is present at all the green, red and red/white wires at the ECU, and that all brown and brown/orange wires are earthed.

[Speedtouch]

Sounds like classic symptoms of a duff ignition coil to me but you say you've replaced that - was that with new or used?

Do these have a ballast resistor in line with the coil?

[daimlerman]

Sounds like classic symptoms of a duff ignition coil to me but you say you've replaced that - was that with new or used?

Do these have a ballast resistor in line with the coil?

Swapped coil for a known good 'en.

[daimlerman]

Coil only showing 6v now!
At the ECU plug;
Green,red,showing 12v,no red/white.
Calling the black top right at the ECU plug;
3.brown/green
5.brown
15.brown
middle row,
4.brown
14.brown with a green patch?
17.brown
l/h row,
5brown/blue
15.brown/black
16.brown/blue
All above shown no continuity to earth,all other brown,brown/other colour do.
No spark with a plug direct to the coil.
Coil is remaining cold.

[E30BeemerLad]

If another coil is needed Malcolm I have the used spare one from the M40 days of my touring, which you are welcome to, I can post to you but you won't see it until Monday/ Tues at the earliest

[daimlerman]

Just swapped the coil over again,other one gives 12v,dropping to 9v when cranking.

[daimlerman]

Red,red/white at DME and FPR showing 12v.

[daimlerman]

Pins 2, 14, 19, 24 should all have direct contact to ground.

Image of plug.



Also, Murran was having a similar problem with his M20B25 engined e21, he grounded pin 48 and the car now runs. Check posting http://www.e30zone.net/modules.php?name ... 25#1624425

Thanks,Will,it's cold and dark here now so I will be onto this in about 13 hours!
Can you tell me the pin number for the black wire,please? Should be 1,38,55 or 19.....

[daimlerman]

Black wire to coil is on pin 1.

Thank you,now I can trace the others with less risk of errors!

[daimlerman]

Earths all show continuity,tried the 'Murran mod' but it's not worked for me!

[Speedtouch]

Worth checking that +12V is reaching the correct pins of the ECU socket;

http://www.autolib.diakom.ru/CARS2/

Click on BMW in the left-hand margin, then 4th link down, then 'Mitchell on Demand' for wiring diagrams.

For a 1992 318i for instance, +12V should be on pins 26 and 64.

[daimlerman]

Thanks for your support,Will!
I am satisfied with 1,2 ,4,5,6 and 8 from your hit list;my gut instinct made me suspect the coil from the off,but swapping in a handy s/h one from the project cabbie made no difference... however,I have a new one on order!
I've done the trick with the fuel pump relay and can hear the thing running,cranking the engine with the hose clip loose for fuel delivery gives me a petrol leak,so I am satisfied that the pump comes on line as it's supposed to.
This started with an intermitent fault,something cutting all power,when the engine cut,the rev counter dropped to zero immediately,even though the car was in gear and coasting at speed.... Be Monday AM now before I can do a check at the fuel pump,taking the wife to a BMWCC doings tomorrow!

[Speedtouch]

Nothing to do with that green wire under the dash that leads from the ignition switch to the OBC immobiliser, is it - that's caught quite a few Zoners out in the past after engine swaps!

The intermittent nature of it suggests a loose connection somewhere, rather than a component fault, though it's worth checking that the ignition switch supplies a reliable switched +12V, as they're bound to get a little worn after 20 years.

[Brianmoooore]

though it's worth checking that the ignition switch supplies a reliable switched +12V, as they're bound to get a little worn after 20 years.

Done - 1/3 of the way down page 2.

[daimlerman]

Nothing to do with that green wire under the dash that leads from the ignition switch to the OBC immobiliser, is it - that's caught quite a few Zoners out in the past after engine swaps!

But the thing ran perfectly for a week!
It does have an OBC,but I have never worked out the immobiliser...tell me more...

[Brianmoooore]

It does have an OBC,but I have never worked out the immobiliser...tell me more...

The OBC immobiliser is a well known cause of no spark based running faults, but not if a 12 volt bulb connected between ignition coil + and earth lights when the ignition is switched on, and remains on while the engine is cranked.
These voltage checks must be made with a bulb, not just a meter, as the extremely low current needed by a meter can give very misleading results!

[Speedtouch]

If the rev counter is dropping to zero, could it be worth temporarily removing/disconnecting the clocks in case the SI board batteries are failing and causing a short of the ignition circuit perhaps?

[Rav335uk]

Maybe this won't help, and i appologise, but have you taken the battery off and then reconnected it back again, as this would reset the OBC???

[town325i]

are the nuts nuts tight on the coil. i had this trouble a few years ago and it was all down to a loose coil nut on the live side m40b16

[daimlerman]

Just started again with this.....
Fuel pump runs when FPR is bridged,but not with a relay in place.tried three relays from stock with the same result.All three relays function correctly when tried in my sole remaining running car,so what's happening?
Power to the relay contact,
Wire intact to the pump,
Fuel arriving at the rail,
But still no sodding spark!

[SPADGE]

Just started again with this.....
Fuel pump runs when FPR is bridged,but not with a relay in place.tried three relays from stock with the same result.All three relays function correctly when tried in my sole remaining running car,so what's happening?
Power to the relay contact,
Wire intact to the pump,
Fuel arriving at the rail,
But still no sodding spark!

Malc

Are you sure you have melted some wiring?

It has been mentioned already but you have swopped the engines over and how sure are you that you didn't have the problem in Brians thread in the engine conversions section?

All the best

Jules..

[Brianmoooore]

Fuel pump runs.........,but not with a relay in place

Just with the ignition on, or when cranking as well?

[Speedtouch]

It's not something silly like a blown fuse is it?