Yeh, quite a bit of trouble with the plunger, coil gets weak as it gets hot, there not that expensive so it would be the best place to start. Love faults like this, ones that jump back into life as soon as the truck see's an engineer pull up on site!

You don't say if all the lights stay on at the dash board when the truck chucks it? Assuming they all go out maybe a dodgy fuseable link?

Assuming they stay on maybe a blocked fuel filler cap not allowing tank to vent and causing a vacuum in the tank?

The small 90 degree inlet pipe into the primer head gets blocked quite easily, take the filter off and blow through the pipe into the head.

I assume it's the same spec as the UK and has a DPA pump on it? I had a sneaky little one once, years ago whereby the return from the pump was collapsed internally and was causing an in-balance inside the pump. The return pressure was equal to the inlet pressure and it just kept on bailing out every now and then. Never happened since but it's one of the ones you never forget as it was that weird.

Sounds like fun, no doubt it'll raise it's ugly head again in about 6 months time!!

LOL!!