We had a similar problem with the single
level engine control on our Perkins 4.108
, in the shifter linkage - sometimes it worked fine, sometimes shifting seemed to hang up. I couldn't find anything that looked wrong in the shifter, cables
or linkages. Finally the transmission
stuck in forward, no neutral or reverse.
Turned out the cable had corroded internally - the cables consist of a vinyl outer case, a hollow twisted cable, and a solid core
that is the actual moving part. The twisted cable had corroded thru and was hanging up the core
. It only became apparent once the corrosion
finally burst thru the outer vinyl case. The cable ran under the engine heat exchanger
, where engine vibrations had worn a small hole in the vinyl cover allowing seawater to penetrate into the twisted cable. The cable was right beneath the pencil zinc, so every time anyone checked or replaced the zinc, the cable got a saltwater bath and some saltwater entered the cable, leading to the corrosion
and eventual failure.
So, if you check the pump and follow the other suggestions above and you still haven't found the fault, you might disconnect the engine end of the throttle cable and see if the internal core runs freely when you advance the throttle lever - if it seems to hang up, the cable may be suspect.