This is one of the vans they use at work & my boss asked me to look at it for him as I used to work with cars heaps... never touched diesel though which is why im asking you guys for advice before I start pulling things apart & working out how it all works the hard way.

So your boss is paying you to look at it and you don't know about diesels?

The business must be in trouble.

 

no, im looking at it in my spare time... anyone have any tips or advice?

 

Ask your mechanic to check on the engine for oil leak, and your starter for possible oil intrusion. If there's no problem, check your battery. It might have been drained while you're starting your van. Check also your alternator and belts. And the least, check if you have enough diesel in your tank.