M40 running issues,test bulbs fitted....

[daimlerman]

I can only make the fuel pump run when the relay is shorted,relay works properly in my other running car,tried three relays,same result.
I swapped the ECU for the spare from Spadge,not sure now which is which ,but with one of them I got a flash of power at the pump that gave a spark and made the engine cough,but not run...but nothing repeatable.I have checked the resistance reading for the CPS at the ECU plug and have 550 ohms.
Is this something to do with ECU?
Cannot understand that 2 would fail...
Will is suggesting that ECU or CPS,CPS is new and checks OK,ECU swapped for a s/h replacement,what next?

[Speedtouch]

[quote="daimlerman"]
Fitted new CPS,now I do not even have a spark...
[quote]

I'd be tempted to try the old CPS again.

[Brianmoooore]

The fuel pump switching circuitry, inside the ECU is mostly the same as that which produces the sparks. You implied that the fuel pump was running when cranking, so this is what we were struggling to accept!
Things make much more sense if there is no spark AND no fuel pump switching, but unfortunately, we're not nearer to the cause!
The ECU is not seeing crank sensor pulses - this can be because of a duff crank sensor, a duff ECU, lack of power (lives and earths) to the ECU, a duff DME relay (comes under 'lack of power', in effect), or a fault in the wiring joining it all together.

[sihooker]

I swapped the ECU for the spare from Spadge,not sure now which is which ,but with one of them I got a flash of power at the pump that gave a spark and made the engine cough,but not run...but nothing repeatable.

I'd be looking for a broken/shorting wire somewhere near the ECU cos it sounds like when you replaced the ECU you disturbed something.

Maybe undo the cable ties that hold the wires coming out of the ECU and give them a bl@@dy good wiggle whilst trying it on the key?

[daimlerman]

This needs explaining to me in words of one cylable that an idiot can understand.
The last time this engine ran was briefly last Monday afternoon....
I have just turned the key and it started and ran perfectly..........for about 30 seconds.......
So it must be getting fuel,it must be getting a spark,why will it not keep running?

[sihooker]

Cos it's a 20 year old bitch??

Sorry,i know that's no help,but i do feel your frustration...

[Speedtouch]

Check the spark plugs - if they're all sooted up, it indicates overfuelling, which could be down to a duff fuel pressure regulator or blue temp sensor.

[Brianmoooore]

When it died, did the rev counter drop instantly to zero, or decay with the engine speed?
An intermittent fault like this needs some monitoring lights wired up! Connect a bulb or LED across the fuel pump terminals, and another one between coil + and earth, and tell us if either of these goes out before/when/after the engine cuts.

[daimlerman]

Check the spark plugs - if they're all sooted up, it indicates overfuelling, which could be down to a duff fuel pressure regulator or blue temp sensor.

Maurice,ten minutes ago the rotten,sodding thing fired and ran perfectly,for 30 seconds or so,just long enough for me to remove/stow the battery charger leads,sounded perfect,idled at 600rpm steady,now there's buggerall again!
Dunno about rev counter this time,I was stood by the front of the car when it died,refuses to repeat it's self.
Anyone got a shotgun?

[SPADGE]

Anyone got a shotgun?

Paypal?

[Speedtouch]

Maurice,ten minutes ago the rotten,sodding thing fired and ran perfectly,for 30 seconds or so,just long enough for me to remove/stow the battery charger leads,sounded perfect,idled at 600rpm steady,now there's buggerall again!
Dunno about rev counter this time,I was stood by the front of the car when it died,refuses to repeat it's self.
Anyone got a shotgun?

Sod the M40 donk and fit the Daimler V8 in there

[daimlerman]

When it died, did the rev counter drop instantly to zero, or decay with the engine speed?
An intermittent fault like this needs some monitoring lights wired up! Connect a bulb or LED across the fuel pump terminals, and another one between coil + and earth, and tell us if either of these goes out before/when/after the engine cuts.

Right!
Test bulbs made up and fitted between battery neg and coil pos.
This one is bright when ign on,dims a little if the engine fires.
Bulb across the fuel pump lights with ign,stays bright if the engine fires but is mostly out.That is,it comes on,then goes out when cranking.Just every now and then it stays on,but not long enough for the engine to catch.

[daimlerman]

[Speedtouch]

Try running a direct feed from the battery +12V terminal to the fuel pump and see if the engine stays running.

This will at least establish whether it's the pump at fault, or the supply/switching to it.

[mick_318is]

Malc,

After each time it fires / dies. Can you start it again or does it just refuse to start. I had a similiar problem with a M20, where it would fire then die after approx 30sec. After it died I was not able to start it again. One thing I found was that if I unplugged the CPS lead and then plugged it back in straight away, it then would fire and then unfortunately die again. I could repeat this process over and over again.
Now I never found out why this was happening ( scrapped the car ) though it could help pinpoint the problem for our technical Gurus.

[Brianmoooore]

Test bulbs made up and fitted between battery neg and coil pos.
This one is bright when ign on,dims a little if the engine fires.
Bulb across the fuel pump lights with ign,stays bright if the engine fires but is mostly out.That is,it comes on,then goes out when cranking.Just every now and then it stays on,but not long enough for the engine to catch.

In that case, it goes back to this: "The ECU is not seeing crank sensor pulses - this can be because of a duff crank sensor, a duff ECU, lack of power (lives and earths) to the ECU, a duff DME relay (comes under 'lack of power', in effect), or a fault in the wiring joining it all together."

All we've established is that the ignition switch and any conventionally connected immobiliser are innocent, and that occasionally the ECU does see crank sensor pulses, and does with them what it should!
Try measuring the resistance of the crank position sensor at the ECU plug.
I can't find my copy of the ECU pin connections for a M40, but willnz should be able to tell you when he comes along.

[daimlerman]

Checked CPS at the ECU plug and it read 530ohms....
Later today(just in from work!)I will try the 'Murran mod' with this second ECU,then re-fit the original CPS and see what occours...
I am a bit fed up with the thing,the shell is rotten,just wanted to use it to tide us over until the cabbie was finished...looks like it will be broken sooner rather than later!

[Brianmoooore]

This is just to check that there is no cross-connection to the supply wire to the coil. if there is a cross-connetion, it could be disrupting the pulses to all of the components above.

Wouldn't affect the fuel pump switching though, so seems unlikely!
Are we certain the ECU is switching the DME relay on with the ignition?
Try removing the relay, and using wire links between pin 30 and the two 87's to bypass it.

[Speedtouch]

Did this ever get solved in the end?

[daimlerman]

Did this ever get solved in the end?

In a way,I stripped out all the 'good' bits and weighed in the remains for £86.60....
No car trys to better me and lives!
I came to the conclusion that I had an intermitent fault possibly in the engine loom somewhere...
This was always a 'stop gap' car once I had removed the bits I wanted for project cabbie,been better if it had run over the winter,but that's life!
It is'nt me that has to walk to work for a while,it'l make the wife more grateful when the cabbie comes out for use!

[Speedtouch]

That's the spirit - that'll teach that troublesome turd!