Bad cold starting - old fuel?

[DubDick]

I've got a '99 2.5TDi camper conversion which is normally laid up through the winter. Just pulled my baby out of hibernation and put her through the Mot - no issues.
She's been sat for about 7 months and started about twice in that time.

Anyway prior to bringing her back out I gave her an oil & filter change. Friday I took her for the MoT and this when she first started to be difficult to start, but it could have been getting worse each time.
It turns over fine, catches and runs for about half a second or so and then stalls. It'll do this about three times and then run fine. Alternatively I just hold the start motor in for a while longer than I normally would and eventually she'll catch. She chugs at around 500 rpm and then manages to raise to about 800rpm and runs like a beetle for a 30 seconds or so, then will be fine. Power is good and starting is fine when warm.

The fuel in there is 7 months old but it's not the first time I've left her sat through the winter.

The injectors are slowly getting worse as she smokes a bit until warm. I heard this is common with engine that sit for long periods as it allows build up on the injector. I do have some bigger Bosch ones to put in there - they'll be installed in a month or so. These injector have been cleaned out and I've ultra-sonic cleaned the nozzles. Thing is I hate making a change to my engine when it not running fine to start with.

Anyway - this seems a typical symptom of glow plugs, so I thought I'd start there. Pulled one of the caps off and tested for power feed - fine. It gave me just over 10 volts for about 2 seconds once the key is turned and then goes off. I assume the power comes back on once the engine is running.
I tested the voltage feed in each of the 5 caps - all good.

Next I resistance tested each of the glow plugs - all fine (around 1 ohm).

So what next?

Next weekend she's going to get a long run and will easily get through a tank of fuel. Currently has about 1/4 tank of old fuel so that'll be brimmed with fresh stuff to see if that help clear the problem.

If after this weekend I still have a cold start problem I will start the testing again.

I was thinking I could run power through a head light bulb test lead to each glow plug - that'll prove that they are all really taking the power and not going open circuit once heated.

After that it'll be over to VW I think to have diagnostics read and check the pump timing. The cam belt needs doing anyway.

Is there anything I'm missing of should be checking first?

Many thanks, Rich.


History.
1999 2.5TDi 88hp
91 K on the clock
Stainless pipe with decat section.
Intercooler
Tunit box (switched so not always used)
Fuel temp sensor changed previously
MAF changed a few years ago.

[lostboy]

have you drained off the fuel filter after the rest up?

J

[DubDick]

No I didn't, it's all good now though.

After the run, and some fresh fuel, she's back to how she use to be. I guess that the standing and extended idling sessions either allowed crud to biuld on the injector or crud to insulate the glow plug tips.
It could also just be the fuel but it's fine again now.

Cheers, Rich.

[Brian Considine]

As an aside I understand that currently available retail diesel now has up to 10% biodiesel content & that biodiesel is hydroscopic - this could be a problem for vehicles stored or laid up for periods of time.

[DubDick]

Interesting point Brian, my van has been beeen laid up through the winter every year but only the last two has it really sat still as I now don't tax through this period. Last year I think I just let her sit until ready - she was fine. This year I starter her and let her tick for a while a couple of times. Then I did an oil & filter change which involved further running, mainly at idle. Each time she was getting more difficult to cold start (I think) until the point I realised it was a problem.

I think next winter I'm just going to let her sit and resists the temptation to turn the key.