naughty engine!

[tomsneade]

Hi, I have a 25 yr old VW 25 diesel transporter and sometimes the engine fires up first time (I always pull out the cold start knob) and sometimes, like today, (nice and warm) it really struggles and can take a couple of mins before turning over...Any mechanically minded folks out there who could give me any clues? Many thanks in advance for any help. Tom.

[kit]

I had to fit a non return valve on the fuel line between the pump and filter, but I sometimes still get the problem you are talking about, old engine.