The Duchess is being a little minx again!

After running perfectly as a DD for a couple of weeks she refuses to start. She has sometimes needed a couple of hits on the key when starting from cold, but has always started, nearly always immediately.

Suddenly she won't start at all. She cranks fine but there's no hint of any pots firing. Th8s is just a whinge really as I haven't bothered with any diagnosis yet but I'll post up results as I get round to them.
I'll start with a Nanocom scan, fuel pressure and try taking a spark plug out to test for a spark.

My money is on the CPS right now but that's a flat out guess until I have any data. I'll check before loading the parts cannon!

If anyone has suggestions on what to test, please let me know (apart from my head for still running this vehicle! 😀)

Crank sensor, or make sure the immobiliser code matches between the engine ECU and the BECM, as a Thor will crank but not fire if the code is incorrect.

Remember, a thor will crank even when immobilised, sometimes they have a fit and go into lockout, a job for Marty I’m afraid..

A less likely but possible cause is erroneous coolant temp reading - check it is reasonable. If its showing something like 140+c, it will be adjusting the fuelling way off and won't start.

Somewhat anecdotal but it was the cause of my random no-start issue a few years back. The wiring on the sensor plug had been twisted, the insulation cracking caused intermittent shorting. Just something to check under the live data :)

I didn't realise they'd crank when immobilised, thank you folks!
I'll have a go at this tonight when I get in, I'm missing my heated seats already :)
The Jeep is feeling smug now it's back on DD duty, so it'll probably find a way to let me down too!

I've been back in my BMW for a week or so as its been sat there costing me money... at the right time too!

BMW's heated seats are like having a small fire under your arse, unlike the P38s 'kind of warm by the time you get to your destination' attempt. Wonder if the L322 (sorry, X5..) also gained decent seat heaters from BMW.

Well, she's running again. I logged in to have a look at the faults in the BECM and found these:

PO333 Knock Sensor Fault Bank 2
Drive Cycle B
Occured once
Signal too low
(not currently present)

P1668 = Anti Theft Alarm Serial
Link Fault Drive Cycle A
Occured once
Signal Too Low
Fault not currently present.

Then I tried starting her and she fired first hit. I cleared the faults for the hell of it and they didn't come back. Does the Anti Theft alarm cause a no -start? Does anyone know the cause?

She was quite rough until she warmed up a bit and on the "Roughness" page of Motronic pot 4 was showing values up to about 7. The misfire count was 0 all round.
I suspect it's time for some spark plugs, so I'll whip a couple out to have a look.

While I was in there, I had a poke around - what is "Moisture Detection"???

Anyway, I've got a running car - I'm just a little wary as it's a fault for which I don't have a cause.

EDIT: Immobiliser was showing "Disabled"

Morat wrote:

EDIT: Immobiliser was showing "Disabled"

That just means passive immobilisation is disabled so it doesn't immobilise itself when you unlock it but don't start it within 30 seconds.