Hi folks,
the fun has begun again. I foolishly filled the Duchess with fuel and she immediately went into a sulk.
She'll crank all day but no start. The first crank came with a bit of a cough and 3-4 cylinders fired, nothing ever since.
In the past she was getting temperamental and would do this, then start perfectly after an hour or so. To try and fix that she had new plugs, wires, and coils and the problem seemed to be solved.
However, it was only ever a problem in the damp and the weather has been rubbish recently.
On Richard's suggestion I slapped the EKA in, no change.

I'm wondering - could it be the chip in the (only) fob? or is that ridiculous? The remote functions work OK (pretty much). Is there a way to know if the transponder in the fob is goosed?

Otherwise, I guess I need to get a plug out and check for spark when I have a minute.

Nanocom showed "adaptation out of range Bank1" 5 times when I first checked it. I've cleared that and it hasn't come back, which I guess isn't surprising as she hasn't run since!

Clues if you have them please, I'm all out!
Morat

There is no transponder in a P38 fob as such. If the remote is operating the locking, it will also be arming/disarming the immobiliser.

EKA will stop it cranking too. The engine ECU and BECM could be out of sync however, which on a Thor WILL still crank with no signs of firing - check the codes match. But if you had it coughing to start with, that is unlikely.

Next I'd be thinking the crank position sensor. Also check what it reports the coolant temp is - anecdotal but I have personally had it read 140c+ on a cold engine, which caused a no start with nothing else looking out of the ordinary. Turned out to be twisted wiring with cracked insulation at the plug on the sender in my case.

Like Sloth said: +1 for the CPS: Faulty one does not throw up a Fault Code either of course

I'd guess at crankshaft sensor here too.

There'll be no fault code, however, if you use diagnostics, and try cranking the car you'll not see any rpm whilst cranking.

David.

All great suggestions for narrowing it down - thank you!
I'll report back :)

Failing CPS would explain why it is intermittent and also why it will try to fire but not catch. If it was out of sync, it just wouldn't try.

As Sloth mentioned - on a Thor, it will crank all the time, it just won't fire if it's out of sync.
GEMS petrol are the only p38's that won't crank if it's out of sync - EDC and Motronic will always crank, as the immobilisation strategy is it same, and the engine ECU doesn't respond to the BECM on accepting of a correct code like the the GEMS will.

Another +1 on the crank sensor though. In Nanocom/Motronic and maybe inputs/general 1 or 2 (could be wrong but it's in there somewhere!) there's a 'tooth count' parameter, which shows how many counts the ECU has done from the crank sensor. If this isn't registering counts, then it's not seeing anything from the sensor.

You mentioned "after filling with fuel" it wouldn't crank, a failing cps is far more likely to play up when hot..

Try giving it a spray with some freeze spray and try again..

OK, that's weird.

I cranked it and saw 0 rpm change to 155rpm. Coolant temp was a reasonable 15 degrees.

First crank caused a bit of a start and it died in half a second. Almost like it had a tiny amount of fuel but wasn't getting any more...

So I found the fuel pump relay option on the inputs page and flipped that on to see if I could hear the fuel pump running. I couldn't but that could just be my ears.

I flipped it on/off a few times and cranked again - perfect start.

Assuming the fuel pump relay works as I think it does, I wonder if the fuel pump isn't priming properly and maybe I have some leaky injectors which are reducing the fuel pressure after a few days sitting idle? Weirdness.
I'll see if it starts again in an hour or so.

Not a P38, but I've known crank sensors to play up intermittently for a long while before they suddenly fail, The last one I had fail did so after filling the car up, got halfway out of the petrol station and it then would crank but not start. I'd been chasing running issues for a while before that which were cured with the new sensor.

I guess the crank sensor isn't necessarily in the clear yet - but it was registering engine speed every time I cranked the car but it only started once (after i'd messed with the fuel pump).
Time to get the fuel pressure gauge out as well!

In that case, it does sound far more like a fuel delivery issue - where that be a bad relay, (or fuse box even?) Or maybe the fuel pump itself is starting to get weak.

Definitely worth checking fuel pressure.

If you're registering rpm when cranking, then I would think unlikely to be crank sensor - it is a common culprit, yes, but if you get a reading and playing with fuel pump on/off made a difference, I'd definitely investigate that first.

My original fusebox started playing up years ago so I pulled it apart and gave it a going over, soldering any dodgy looking joints and putting wire links on any tracks that looked to have been getting warm. It was fine for 5 years or so but then one of the spade contacts for the petrol pump relay went intermittent. Ordinarily it fires up on petrol then almost immediately switches over to LPG but fortunately I can start on LPG. As a temporary fix I ran a wire from the engine ECU directly to the relay so bypassing the connection in the fusebox but replaced the fusebox not long after.

Hmmm, I could really do without replacing the fuse box.. but - is there a way to inspect it that isn't too destructive?

Unplug the fuel pump relay and use a small screwdriver to see if any of the spade terminals under the plastic wobble. If they do, there's a cracked solder joint where the terminal joins the circuit board.

I had another conversation with Richard while he was on the Autoroute... and we reckoned it's probably leaky injectors.

But, before I go down that route - is there a non-return valve in the P38 fuel system? I'm guessing that if there is, mine could be goosed.

Have you tried starting on gas?

Would rule out petrol system entirely.

Hmmm, I'm sure it's the petrol system as running the pump long enough ensures a good start but it'd be interesting to see if I can even start on gas.
Simon fitted it, I'll have to ask him for the magic combo.

May well be - just rules other things out for sure.

I think on omvl based systems, unplugging the control button will force it to start on gas? Or holding the button as you turn the ignition on - I have managed it before but I'm now lacking two cylinders and both petroleum and lpg...

Thing is, I can't find out for sure if there is an NRV type thing in the fuel system. I'd assume there's one on top of the fuel pump, but assumptions....