Engine cutting out.

[Switch]

Good afternoon all,

I'm having trouble with my 2000 Mk1 Tuscan.

Last Friday it cut out at 70ish on the A34. The engine just died, everything else stayed on.
Had it recovered back home.

It will start up, and run for 10-11 seconds consistently before just cutting out again.
Fuel pump primes, engine fires up normally and runs as it would usually. RPM doesn't seem to have an effect on the duration it will run for.
ECU shows greens on all sensors.
Logging the data to the laptop from the ECU the data just STOPS with the engine running, rather than indicating a/the problem.
Replaced the fuel pump relay, no effect.

When it cuts out it does not splutter or stutter, just dies.

Any thoughts?

It's going in for Mat Smith to look at it in a month or so for service + this, but I'd like to to get it moving before then if possible...

[Polly Grigora]

It might be worth your while to first check if there is an ignition supply to the fusebox and ignition coil when it cuts out

[NMNeil]

When it cuts out is it abrupt (electrical) or does it slowly stop (running out of fuel)?

[PetrolHeadPete]

Surely must be immobilizer?

[NMNeil]

PetrolHeadPete said:

Surely must be immobilizer?

Of course, what else could it possibly be?

[spitfire4v8]

PetrolHeadPete said:

Surely must be immobilizer?

yes a quick check might be to see if the red LED on the immobiliser key thingy starts flashing as soon as it's cut out? If it's consistently the same time scale before the engine stops then something like that is favourite .. most things cut out randomly not on a timer but the immobiliser reset would be the same time every time? Otherwise as Polly says you need to get a test bulb and start checking ..

[Cockey]

This happened to me some years ago and turned out to be the fuel pump relay failing.

[Switch]

So before diving into the fuse box with a test lamp...

I paid close attention to the rearm timer on the immobiliser (15-20 seconds or so).

And what do you know, the cut out lines up with the re-arm timer.

Example press key button, immediately start and engine dies approximately 10 seconds into running.
Example 2 press key button, wait 6 seconds then start, engine dies in less than 5 seconds


And the LED starts flashing next to the slot as soon as it dies....

So what are my options?

[spitfire4v8]

I'm not big into immobilisers but i would imagine there's a 12v feed from the ignition which tells the immobiliser to remain disarmed until the ign is switched off, then wait 11 seconds or so and re-arm. This would appear to be missing in your case. Look for an immobiliser fuse?

[Switch]

That would make sense.

It seems that either the immobiliser doesn't know the ignition is ON, or it doesn't know that the engine is started and running. And thus re-arms automatically.

Time to go fuse hunting...

[Polly Grigora]

spitfire4v8 said:

I'm not big into immobilisers but i would imagine there's a 12v feed from the ignition which tells the immobiliser to remain disarmed until the ign is switched off, then wait 11 seconds or so and re-arm. This would appear to be missing in your case. Look for an immobiliser fuse?

Switch said:

That would make sense.

It seems that either the immobiliser doesn't know the ignition is ON, or it doesn't know that the engine is started and running. And thus re-arms automatically.

Time to go fuse hunting...

Verifying you are both bang on the case

[Switch]

That would seem to be the culprit...

Now I just have to find the two relays that are in line with the circuits and temporarily bypass them. Any clues as to where I should be looking (I assume in the driver's footwell, somewhere between the m36 and the MBE ECU...

ETA: it would appear that the relays are inside the M36. So I'll be needing to find the splice I would imagine...
Any hints would be greatly appreciated.

Edited by Switch on Friday 22 April 12:58

[Stig]

NMNeil said:

Of course, what else could it possibly be?

This post didn't age very well

[NMNeil]

Stig said:

NMNeil said:

Of course, what else could it possibly be?

This post didn't age very well

It received the standard reply from many PH members, don't do any diagnosing, just rely on guesswork and load up the parts cannon.

[Polly Grigora]

[Switch]

A temporary solution.
Latching relay created using a Y from the ignition fed +12, with the coil energised from the ECU power feed relay initially, then once it cuts out(the fault), powered using a loop back from the output of the relay.

Once the ignition switches off, the relay unlatches until the the immobiliser is disarmed again by the fob.

Meaning the immobiliser is still in play, you can't turn over the starter without it disarmed, and once disarmed the ECU will stay on till the ignition is switched off.

Easy! (Not pretty)

[s6boy]

NMNeil said:

It received the standard reply from many PH members, don't do any diagnosing, just rely on guesswork and load up the parts cannon.

Hardly. It seems the responses were spot on with no need to load up any parts cannon! All within a couple of hours and not surprising when you get answers from some of the most knowledgable people on here. What did you contribute?
I might be being over sensitive but find these sniping comments getting very boring, negative and in this case unfounded in what's usually a positive part of PH with the help and support on offer.

[porterpainter]

Switch said:

A temporary solution.
Latching relay created using a Y from the ignition fed +12, with the coil energised from the ECU power feed relay initially, then once it cuts out(the fault), powered using a loop back from the output of the relay.

Once the ignition switches off, the relay unlatches until the the immobiliser is disarmed again by the fob.

Meaning the immobiliser is still in play, you can't turn over the starter without it disarmed, and once disarmed the ECU will stay on till the ignition is switched off.

Easy! (Not pretty)

Good work!

[Polly Grigora]

Switch said:

Nice emergency fix

Don't know if you did much checking through the circuit, the following might help if you fancy a crack at it

Immobiliser ignition sensing is fused, see Fuse 27




The fused ignition output can be found at fusebox connector C, shown below

See 4.4(pin) G(green cable) 0.5 (mm CSA)



and also shown below at plug moulding cavity 44



The thin 0.5mm CSA Green cable runs from fusebox to immobiliser and can be found at its plug moulding cavity 1

---

If it were my car I wouldn't be driving it until having found the reason as to why the ignition sensing is missing from the immobiliser circuit as it's too risky, yes there could be a simple fault that couldn't possibly cause any other problems, on the other hand there could be a major wiring harness or fusebox fault that could cause major damage to the vehicle at any time

Edited by Polly Grigora on Saturday 23 April 08:26

[Switch]

Thanks for the info. Very helpful.

I've traced and checked the fuses.

The ignition sense feed is getting to the immobiliser, it just feels like the immobiliser has lost the ability to latch.

I've spoken to the usual suspects(Carl, HF etc)

A replacement immobiliser will be sourced shortly (with associated bits of course)