BLS Engine Issue

[redfella]

'06 MK.3 / 1.9 TDI BLS / 198k

Not exactly sure what topic folder this belongs in...
I've recently ran into with the caddy, which I originally put down to shitty fuel.

Van was running on fumes and I filled up at the nearest filling station at the time.
Day or two later the van has issues shortly are starting a new journey.
Van starting juddering and jumping under acceleration - I started and stopped the van (while rolling) a few times to try and get it to reset.
The van battery appeared to get weaker and barely restarted the van - it could have been a bump start while rolling.

I'd since found out the filling station is known for selling adulterated muck for diesel - so i replaced the fuel filter thinking the dirty diesel was the issue.
It drove fine for a day or two afterwards so I thought it was down to the fuel.

It then happened last night for a second time - this time it left me completely stranded.
The van completely failed to restart and the lights even dimmed to a point the hazards wouldn't work.

I have no idea what it could be - bad battery / chassis grounds ?

Any ideas ?

**Small Edit**
I do remember that during the first incident the Tacho dropped to 0 RPM but the engine was still running - so possibly a crank position sensor ?

[STP]

Check the battery voltage, if it's below 12 then it's going bad. Could be the crank sensor too but normally that would cut the engine out every time, even briefly. Struggling to turn over and dull lights, I'd be all over the battery and earth / cable connections and check nothing is slack on the front of the fusebox (the metal strip at the front is your main high current fuses for alternator / battery live/ power steering etc.