Re GordMay's link - I think the problem people have with the Prima 50 and the Volvo
version of the same engine's manual priming pump (they both have the same pump) is finger trouble. The engine
has to be rotated until the drive cam allows the pump to be operated freely manually by the plunger - it will operate freely when the cam is in the correct position but with no travel or restricted travel otherwise. If it is forced then the problem encountered in the linked to thread will occur.
Re the original problem-
I am not familiar with the injection pump on the Prima, but am with the Volvo
version of the same engine
, but offer the following just in case useful -
If the Prima uses the same stop solenoid as the Volvo version then the stop solenoid is energised to stop ie it is not energised when engine is running (so opposite, I think, to most automobile engines but similar to many marine
Regarding timing; as has been said this is unlikely to be a timing matter but if looking for timing marks as wanted to do then if the same as the Volvo (and most likely is) then the pulley driving the IP has two marks, one for the turbo engine and one for the normally aspirated engine (marked "A" and "B" from memory). The crankshaft to camshaft timing is done by use of timing pins to pin the crankshaft and cam shaft in the correct positions, not by marks, and and these must be pinned before the IP timing mark is aligned.
While it is pretty straight forward to time the engine I would not recommend trying without having the service
manual. The camshaft pin goes in through the top of the cam cover just behind the timing belt case (I think I can see the set screw that normally closes it in the photo
in GordMay's link) and the crankshaft one through a hole on the starboard forward side of the flywheel housing. If trying it, use phillips head
screwdrivers or drills of approx the right diameter if don't have timing pins and be very careful with the water
pump and timing pulley screws, using good fitting sockets or ring spanners, as they can be very tight and small enough so the heads are easily damaged (especially the water
Another suggestion - has the manual fuel
stop actuation on the IP been checked to see that it has not been jambed away from the run position?