Running problems

[Paulymojo]

Hi guys I'm new here, I've been making biodiesel for about 14 years now so not a novice. My car (golf mk4 pd) was running fine on biodiesel then I had problems sourcing methanol so had about a 9 month break.
Since I started using bio again I've been having rough running problems, feels like not firing on all cylinders and is worse at cold start. I've changed the fuel filter about 4 times to be well on the safe side so that's not the issue.
I'd appreciate any suggestions 😊

[Julian]

What do the fuel filters look like when you change them?

[Julian]

Oh ... and welcome!

[RichardP]

You could do with getting VCDS on it and seeing what everythingis doing, like injectors, torsion value etc, it may just need a little tweak here or there.

[Paulymojo]

Hi first fuel filter looked pretty dark but after that all OK, I've had a done a few diagnostics, first it was injector 1,then I replaced it, the was showing injector 1,3and4,then after no work showing only injector 1.
Im thinking maybe a fuel supply problem? Maybe the lift pump? Do you guys think that could be a possibility?

[Paulymojo]

I forgot to say thanks to all for the responses 👍

[RichardP]

What diagnostics did you do and what was showing for injector 1, then 1,3 & 4.
The in tank pump would affect all injectors, but may be worth cleaning the strainer there. Likewise the tandem pump would also affect all injectors.
Could be an issue with the injector loom, worth checking the connections, or replacing the loom.
My daughters Golf MK5 PD had a rough running problem - the cam position sensor was bad so a new one resolved that issue.
If you can't fine anything obvious it may be worth pulling the injectors and seeing if any crap has got past the filters and is fouling the inlets on the injectors, easy enough job, just get some new seals and injector bolts. I've got printouts for the job if you need them.

[Paulymojo]

Sorry forgot to say I replaced the injector loom to (with a quality part not a cheapo) the workshop I take my car to gives free diagnostic so he plugged it in there, I'm not too knowledgeable about that side really he just said it showed as a fault, it only runs well on about b30 right now, which is a shame as I've got over 1000 litres of wvo ready for processing

[Paulymojo]

Also forgot to say new injector seals and bolts fitted too

[Julian]

Dark fuel filter could possibly be diesel bug, but I believe it would need to show more evidence in the filter before it had a noticeable effect on performance.

I have a Golf Mk4 PD on 220,000 miles and the only issue I've had was the injector loom or more specifically the connectors on the injectors.  All I did was to squeeze the connectors with pliers slightly so they had a better grip and it's run problem free since.  Might be worth checking despite replacing the loom replacement (cheap fix).