Fuel injection pump, need advice

[Spyro]

Boat relaunched today, all went fine engine had been running for about 10 mins then suddenly died. I had changed fuel filters over the winter so thought the problem would be air lock. Vented the sytem up to the injector pump and clean diesel came out at the banjo bolt on the injector pump. Undid the connection at the outlet of the pump no diesel flowing tried turning the engine with the throttle open still no fuel flowing from the pump. I removed the pump from the engine. The cam that pushes the plunger in and out of the pump body is going in and out ok.
What could be the problem?
Are there any servicable parts in the pump?

Thanks Ian
Engine is a Yanmar YSB8

PIC of the pump. Inlet on the top, oulet on the left.

 

[earlybird]

It's a long time since my YSE8, but I seem to remember that the pump plunger is spring loaded outwards. Is the internal spring still in one piece?

 

[Spyro]

Haven't opened it up yet but the plunger does spring back out when pushed in. There is also an external spring which is not in the photo.

 

[Spyro]

Internal spring is still in one piece, there is a small ball bearing (valve) which sits at the end of the spring inside the spring housing. this appeared to be stuck as I had to poke it out with a this piece of wire. I have put some diesel in the inlet hole and now can pump it out the outlet with the plunger. I am hoping this was the problem. I dont understand why it would stick after it had been running ok. I shall put it back together at the weekend.

Fingers crossed.

 

[earlybird]

Let's hope that's problem solved ! I don' remember the ball, but it is very simple pump.