Diesel engine cutting out

[Russ the Diver]

I have two D1 20 Volvo Penta engine with around over 500 hours, both 5 years old.
The starboard engine when in use suddenly drops from 1500 revs to 500 never cuts out, but leave it running and the engine picks up revs again and carries on running without any problems, There doesn't appear to be any routine when this happens, although it happened four/five times in the space of an hour and a half.
Any suggestions/comments as to what it might be would be welcomed.
Russ

 

[BACUS]

Hi Russ
I had the lift pump fail on my engine which caused the same sort of fault ?
I am no expert but check fuel filters and fuel delivery to injector pump
Regards
Bacus

 

[rogerboy]

could be drawing air , check all connections and pipes etc and as bacus said fuel filters also.

 

[daveyw]

Are they drawing from separate tanks? Are the tank vents clear?

 

[EuanMcKenzie]

Diesel bug could be the cause. Lumps grow in the bottom of your tank and then get drawn into the lift pipe with agitation. They cause momentary drop in revs then get sucked up the pipe to the filter and you're off again

Are you seeing higher filter fouling and also check your tanks for bug or debris.

 

[pappaecho]

I had similar problems on twin Ford Mermaids, where the port engine would suddenly cut out. The suspect was the lift pump which was replaced but the problem persisted. A very old wise diesel engineer told me story about the camshaft "float" which caused the lift pump lever missing the cam. The next time it happened removed the lift pump and sure enough the cam was offset, missing the lever. Replaced the mechanical lift pump with an electrical lift pump and no more problems

 

[Russ the Diver]

Thanks Guys for all your replies. Will let you know what the outcome is after the weekend.......hopefully!!

Russ