Engine running on after key off/fuel pump electrical feed taken away

We've just had some stuff done on our '96 300TDI Defender - very long story but basically the most recent issue that has reared its head is the engine runs on after the ignition is turned off. If switched on from cold, then turned off immediately, no run on. If we go for a journey, say 20', then the run on is about 5-10 secs. Interestingly the run on happens even if the spade connector to the fuel injector pump is disconnected....!

We have just had the solenoid replaced - when the refurbed fuel injector pump was installed we got Landy home to then discover that there was a fuel leak from the top of solenoid - did wonder why the fuel gauge was going down so fast! So mechanic who installed the refurbed injector pump got a new solenoid from the refurbers and installed it on Wednesday. We discovered the run on issue on Thursday.

Given it happens even if the spade connector is disconnected presumably this points to the solenoid being the problem - is that right or are we missing something?

Thanks

Cornishdefender said:

We've just had some stuff done on our '96 300TDI Defender - very long story but basically the most recent issue that has reared its head is the engine runs on after the ignition is turned off. If switched on from cold, then turned off immediately, no run on. If we go for a journey, say 20', then the run on is about 5-10 secs. Interestingly the run on happens even if the spade connector to the fuel injector pump is disconnected....!

We have just had the solenoid replaced - when the refurbed fuel injector pump was installed we got Landy home to then discover that there was a fuel leak from the top of solenoid - did wonder why the fuel gauge was going down so fast! So mechanic who installed the refurbed injector pump got a new solenoid from the refurbers and installed it on Wednesday. We discovered the run on issue on Thursday.

Given it happens even if the spade connector is disconnected presumably this points to the solenoid being the problem - is that right or are we missing something?

Thanks

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Sounds like it may be sticking until the spring eventually overcomes the friction and shuts it off. You can always stall it in top gear with your foot on the brake if it won't stop.
As the engine runs on the heat of compression I cannot think it is anything else unless there is some sort of hotspot in the cylinder head which keeps the fule igniting.
So I'd take the solenoid out, and see if any part of it, plunger, spring etc is tight. Put it back together and try it again. If it only does it when hot this points to a clearance issue when the metal expands with heat from the engine. Or,sadly, a hot spot!

Or could be the FiP needs resetting as over-fuelling could cause this...

v8250 said:

Or could be the FiP needs resetting as over-fuelling could cause this...

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You know more about diesels than I do, doubtless,
But I can see how this could happen if there was diesel left somewhere in the injection system.
Just cannot see where.
Also wondering why this would "suddenly" start happening if it wasn't there before.
But I am totally open to it being other stuff causing it.

Chief suspect for me would be crud stopping the solenoid plunger fully seating, and therefore not cutting off the fuel completely when powered down, or possibly a weak spring on the plunger..

IMO, it is also worth checking the turbo hoses post IC for signs of excess oil ... unlikely, but it could be a sign of the early stages of a runaway, which really will spoil your day..

v8250 said:

Or could be the FiP needs resetting as over-fuelling could cause this...

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Would this correspond with the fact that it happens the longer the engine has been running/hotter the engine is?

Stanleysteamer said:

You know more about diesels than I do, doubtless,
But I can see how this could happen if there was diesel left somewhere in the injection system.
Just cannot see where.
Also wondering why this would "suddenly" start happening if it wasn't there before.
But I am totally open to it being other stuff causing it.

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That is what we found curious - there was no issue after the refurb of the injector pump with the old (leaking) solenoid, only started with the new solenoid.

Points to new solenoid, but most likely a bit of crud stopping it from seating

Disco1BFG said:

Chief suspect for me would be crud stopping the solenoid plunger fully seating, and therefore not cutting off the fuel completely when powered down, or possibly a weak spring on the plunger..

IMO, it is also worth checking the turbo hoses post IC for signs of excess oil ... unlikely, but it could be a sign of the early stages of a runaway, which really will spoil your day..

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Sorry - what is IC? The intercooler? What do you mean by a runaway? As you can tell I'm not exactly an expert.....!

Cornishdefender said:

Sorry - what is IC? The intercooler? What do you mean by a runaway? As you can tell I'm not exactly an expert.....!

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Yes, the Intercooler..

A runaway is when a compression ignition engine runs on its own lubricating oil which has found its way into the induction system by "nefarious" means.. When it does happen, causality on a mechanical TD is, commonly/usually from failure of the oil seals in the turbo cartridge... there are vids on the tube ..

It is not common - but it is a remote possibility, and I would check for it, given it's a five minuit job ( take the hose off the inlet plenum and look - it if it wet through, then panic!! .. an oil film is normal.. - hopefully, you will find nothing worth worrying about..

Just for completeness - The only way of stopping a runaway is to block the inlet of air to the engine, or stall it, if it has manual transmission, AND you catch it early enough... A runaway will almost always trash the engine, given that the thing is running on its own lube oil, and will therefore not stop until it either runs out of lube oil, or the oil gets low enough that catastrophic bearing failure occurs...

I'll re-state that the chances of this being your issue are virtually nil, but, given it is a an easy check, it is always worth doing...

Today's update - checked for the possible 'runaway engine signs' all good so TYVM
Our mechanic who fitted the solenoid spoke to the solenoid supplier - apparently there was a design change in the solenoid because the old round design was found to be leaky.... The supplier said that our mechanic must have been supplied old stock by mistake. Hmmmm. Anyhoo they will be sending a replacement NEW design (hexagon shape) so we should be getting that replaced soon

@Cornishdefender , hopefully this is good news if only the FiP solenoid. Most of us carry a spare FiP solenoid too as if this fails it will strand you...

Our problem has finally been solved. Took a couple of to's and fro's. 1st the shape of the solenoid plunger was changed - but this didn't solve the problem. Once the engine was up and running at temperature (say 15') the 'run on' was still very much in evidence. So, the next step was to replace the spring - the theory being that the spring wasn't strong enough to close off the diaphragm when the power was switched off, so fuel was leaking past.
The spring was duly changed for a stronger one and hey presto the problem is sorted.
What a pallaver!

That's great result and thanks for sharing

Cornishdefender said:

Our problem has finally been solved. Took a couple of to's and fro's. 1st the shape of the solenoid plunger was changed - but this didn't solve the problem. Once the engine was up and running at temperature (say 15') the 'run on' was still very much in evidence. So, the next step was to replace the spring - the theory being that the spring wasn't strong enough to close off the diaphragm when the power was switched off, so fuel was leaking past.
The spring was duly changed for a stronger one and hey presto the problem is sorted.
What a pallaver!

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Do you have a part number for the spring?

Cornishdefender said:

Our problem has finally been solved. Took a couple of to's and fro's. 1st the shape of the solenoid plunger was changed - but this didn't solve the problem. Once the engine was up and running at temperature (say 15') the 'run on' was still very much in evidence. So, the next step was to replace the spring - the theory being that the spring wasn't strong enough to close off the diaphragm when the power was switched off, so fuel was leaking past.
The spring was duly changed for a stronger one and hey presto the problem is sorted.
What a pallaver!

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Glad it was solved for you!!
"Sounds like it may be sticking until the spring eventually overcomes the friction " not quite right, but interesting all the same!
Well done!

Muddy Yank said:

Do you have a part number for the spring?

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Spring comes with the stop solenoid.

lynall said:

Spring comes with the stop solenoid.

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I could use a beef’d up one. The one that comes with it doesn’t get it done.

Muddy Yank said:

I could use a beef’d up one. The one that comes with it doesn’t get it done.

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But you might find the stop solenoid is not man enough to lift plunger against the beefier spring?
I have run a few 200/300 tdi and never had an issues with the stop solenoid spring.