Mk6 transit won’t start when engine warm

[indacus]

Engine seems to start and run fine from cold or lukewarm, but once normal operating temperature has been reached it will not restart until cool. You turn key and it sounds like engine has started, but it dies as soon as key is released. AA patrol didn’t know what problem was but generated this fault code: System : Engine control 1 - ZZH / Diesel CR/EDC DEN C1.1P068A - Main relay. Error Message : Shutoff too early. He seemed to be suggesting this code was pretty generic and not all that specific. Garage have told me they’re not interested (needle in a haystack…). Please, does anyone have any ideas?! Thanks in advance.

[knobby1]

Engine seems to start and run fine from cold or lukewarm, but once normal operating temperature has been reached it will not restart until cool. You turn key and it sounds like engine has started, but it dies as soon as key is released. AA patrol didn’t know what problem was but generated this fault code: System : Engine control 1 - ZZH / Diesel CR/EDC DEN C1.1P068A - Main relay. Error Message : Shutoff too early. He seemed to be suggesting this code was pretty generic and not all that specific. Garage have told me they’re not interested (needle in a haystack…). Please, does anyone have any ideas?! Thanks in advance.

Probably a lazy starter...ver common.

Lord Knobrot

[Altransit]

On the two occasions that I've had a non-starting hot engine on a TDCi, it's turned out to be a fault with the crank sensor, (or the wiring to it)

[Jim Archer]

As said, it could well be the crank position sender getting swarf from the clutch on it.

Once it's hot and won't fire up, pop the sender out - right rear of crank, sort of 1 O'clock position, 8mm A/F bolt, note rough depth it was fitted - and see if it has metal dust magnetised to it. If it's furry, clean it off, refit, and see if that has sorted it temporarily.

What happens is the Hall Effect coil gradually builds a field in the core in use, that then attracts the swarf, that then builds it's own field that takes time to disipate once engine is stopped, and swarf then falls away til next time.

If that sorts it, expect to do a clutch/flywheel in the foreseeable.

Other thing to check is the push fittings for the fuel filter if it's got to be good and heated up before doing it.

Jim

[marcrbarker]

DTC fault code P068A what throws that code? As I understand p068a gets registrered from a previous time the engine had stopped, specifically the PCM module gets niggly about having one of its 12V power feeds getting shut off while the PCM is still waiting for the engine to actually stop.

What I mean is the "code P068A" could be just a red herring. For example p068a can happen on the older model trannies, when its injection pump low pressure valve rubber plunger shutoff valve - doesn't. That caused the engine to continue run on for 5 secs, throw a red engine fault light and give less throttle response. And wouldn't cause a no-start. Why I say could be a red herring

[richardstubbs]

It probably is the crank sensor - they can start to break down when hot and it's a common fault on many vehicles. I've had at least one vehicle like that and if you leave it for about 20 minutes it'll start and run fine. I'm assuming that it's a TDDi not a TDCi (no wires to the injectors)? Because the TDDi system starts on the position sensor in the injection pump (which will be fine) and then switches to PCM (therefore crank sensor) control as soon as it's going. So it just thinks the engine has stopped and switches the fuel off. If it's a TDCi it could be the same thing or something else altogether... I think the AA guy's right - you get that code if the battery has been off or flat. But you could clear them and see if any come back.

It's worth just changing the crank sensor because it's cheap and it'll probably fix it. It might have swarf on the end but I doubt it because that would affect cold starting too. If it has then bad luck.

[marcrbarker]

Because the TDDi system starts on the position sensor in the injection pump (which will be fine) and then switches to PCM (therefore crank sensor) control as soon as it's going. So it just thinks the engine has stopped and switches the fuel off.

Interesting.
Speaking generally the uncertainty with vehicle sensors and if they're sensing or not... with Industrial Controls (as opposed to consumer products) their sensors have litle 'checklights' that blink when they're signalling that you don't need any more than a pair of eyes to see. And the panel they're connected to also has blinkys. The blinky HDD light light on a computer so useful.. But most people will say: "I'm not paying extra££ to have christmas tree lights hidden under the bonnet" but instead want everything dumbed-down and a discount.
Something like a suspect cranksensor - maybe it's bad or maybe isn't who knows replace the sensor anyway & hope.
Perhaps someone should invent a little adaptor dongle to attach to the sensor connector that gives a blinky light off the sensor signal. If the light carries on blinking while the engine's slowing down stopping you know for 100% sure the sensor's OK. (I know the crank sensor is only mV pulses, the dongle would have a little battery to power the blinky..

[Jim Archer]

... It might have swarf on the end but I doubt it because that would affect cold starting too. If it has then bad luck.

That is the thing, the attracted swarf is a hot engine issue, the Hall Effect sensor builds a small magnetic field in use, that attracts the swarf which then affects the signal quality enough that it then won't start at low response values - the PCM is looking for a sharp rise/step in the signal, the swarf smears that step to more of a ramp, and that doesn't register til it's too late.

Once shut down, the field takes a few seconds to collapse, the swarf - which will now be slightly magnetic in itself - attracts to the iron core of the sender, and both slows the field collapse in the core, and smears the signal at cranking. Once it's cooled, the field is naturally weaker, so the majority of the swarf falls away, til next time ...

Because the TDDi system relies on both pump and crank inputs to fire, it knows it's being cranked, but doesn't 'see' the crank/CPS signal til it's either too late, by which time it's outside the timing window set by the pump sender pulse.

Jim

[marcrbarker]

Oops. Just realised the CPS here is a Hall sensor, digital buffered. Well that's even more robust and reliable (metal dust excluded).
There's a permanent magnet also inside a sensors like this that's why just out the packet it sticks to a spanner and it collects metal dust after touchs the floor. I don't quite get about magnetic field collapse few seconds after shutdown, unless these Delphi ones special, I thought was just a simple magnet.

The actual Hall sensor itself inside is just a tiny matchhead-size 3-legged transistor. VHS recorders had one for video head drum. Detects change in magnetic flux directly, so can work at near zero RPM. So a dousing with metal powder is like a vaseline on the lens. Of course the fine powder collected all drops off while the sensor is being removed, and the mechanic with airline blows out bellhousing. I reckon there must be dozens of good crank sensors thrown away every week.

And being TTL levels output a 'blinky' light on it (HDD light style) would be so obvious an improvement --- but they'd sell less replacements if people could actually see them working and stop working.

That is the thing, the attracted swarf is a hot engine issue, the Hall Effect sensor builds a small magnetic field in use, that attracts the swarf which then affects the signal quality enough that it then won't start at low response values - the PCM is looking for a sharp rise/step in the signal, the swarf smears that step to more of a ramp, and that doesn't register til it's too late.
Once shut down, the field takes a few seconds to collapse, the swarf - which will now be slightly magnetic in itself - attracts to the iron core of the sender, and both slows the field collapse in the core, and smears the signal at cranking. Once it's cooled, the field is naturally weaker, so the majority of the swarf falls away, til next time ...
Because the TDDi system relies on both pump and crank inputs to fire, it knows it's being cranked, but doesn't 'see' the crank/CPS signal til it's either too late, by which time it's outside the timing window set by the pump sender pulse.
Jim

Expect when this occurs the PCM will instantly consider it an error and throw a relavent DTC. What would be the DTC for this?

[indacus]

Thanks for all your replies/ideas. I took van to main dealer to read codes and they said only thing showing was faulty camshaft sensor. Just had that replaced at local garage today but still same issue continues - won’t start when warm but as soon as temperature gauge falls to mid point (75 degrees C) engine will start. Occasionally might work sooner if I start with foot on accelerator, but not often. What should I look at next - starter motor/crankshaft sensor? Garage still reluctant to get involved investigating and I am very much a novice mechanic - all ideas gratefully received!

[indacus]

Also need to correct van type, sorry! It’s not a mk6 but rather a 2011 2.2 tdci mk7 - apologies again!

[marcrbarker]

What should I look at next - starter motor/crankshaft sensor? Garage still reluctant to get involved investigating

What's for sure is if replace components that's not where the fault is then usually results the exact same problem plus if unlucky there's risk of counterfeit/ low quality parts too
May be a good idea re-post symptoms. as I understand, correct if wrong..

2011 2.2 tdci mk7
Engine cranks to start OK with key.
turn key and it sounds like engine has started, but it dies as soon as key is released.
start and run fine from cold or lukewarm, but once normal operating temperature has been reached it will not restart until cool.
problem occur when more than 75 degrees on gauge
No DTCs exept for
DTCs P068 (??? )
P0xx (cam sensor)
No DTC for failed crank sensor circuit (??)
Seems to start sooner with foot on accell.

Any modifications? i.e. any deleted DPF/cat /EGR etc.?
Any other messages or warning lights when problem occurs?

P068 I wouldn't expect cause a no start, but as I understand that DTC can be thrown if PCM power feed had been cut while running.

[indacus]

Morning, no, only fault codes had been p068 which aa guy cleared, and then camshaft sensor. No warning lights/messages on dashboard - just won’t start hot. As soon as temperature drops to 75 degrees though it starts and seems to be running fine/normally - what’s going on?!

[amlav]

Crankshaft sensor ? Pour some cold water on the crankshaft sensor when engine hot and won't start . It used to happen on older type Jeeps too .
Make sure is the Crankshaft sensor ....not the camshaft sensor you pouring the water on to .

[marcrbarker]

Crankshaft sensor ? Pour some cold water on the crankshaft sensor when engine hot and won't start . It used to happen on older type Jeeps too . Make sure is the Crankshaft sensor ....not the camshaft sensor you pouring the water on to .

That sounds easy one to try. An empty dishwashing liquid bottle filled up with water ready to squirt the whole contents over the sensor.
As many have mentioned earlier the cranksensor has a tendency to collect metal dust - but it drops off again. (and from my experience if CPS ever do fail it when hot restart)

@amlav When this crank sensor problem happened with you, did you happen to notice any extra warning light on the instruments? Had you by chance also scanned (Forscan eg.) to see if there was also a stored DTC code ? (ie for crank sensor )