Mark,
The same thing happened with my Perkins 4-108. A very good mechanic thought
that it probably was air getting into the system. He tightened everything,
but couldn't prove that it was air because none of the connections appeared
to be loose. He changed the fuel filters at the same time and I haven't had
a surge since. He suggested polishing the fuel, but the bill on that was
$400 so I elected to change the primary Racor regularly (every 10-15 hours
at first then gradually increasing the time span between changes) which I
did. That was over 200 hours ago and the engine has been running well ever
since. I don't know if the surging problem was air or the filters, but I
suspect air. I have heard the same surge after changing a secondary filter,
which had to be air. The engine evidently gets a bubble of air, the power
drops off and the fuel pump thinks the engine needs more fuel, the fuel
pumps supplies more fuel, the small bubble of air passes while the engine
gets the fuel and speeds up and the fuel pump then goes back to the proper
setting.
Herb Hoffman
My Tyme
Prairie 29
Our trawler has developed a surge. ...Running at
2150 RPM, our normal cruising speed, the Perkins 4-107 sped up to about
2600 RPM and then immediately went back to 2150. ...This continued
happening but on a more frequent basis and
then mysteriously went away. ...Once it starts it seems to come each time
more frequently. Subsequently
any journey of an hour or less produces the surge with increasing
regularity. ...but I would have thought it would die if fuel starved or
ingesting air not surge ahead.
Mark,
The same thing happened with my Perkins 4-108. A very good mechanic thought
that it probably was air getting into the system. He tightened everything,
but couldn't prove that it was air because none of the connections appeared
to be loose. He changed the fuel filters at the same time and I haven't had
a surge since. He suggested polishing the fuel, but the bill on that was
$400 so I elected to change the primary Racor regularly (every 10-15 hours
at first then gradually increasing the time span between changes) which I
did. That was over 200 hours ago and the engine has been running well ever
since. I don't know if the surging problem was air or the filters, but I
suspect air. I have heard the same surge after changing a secondary filter,
which had to be air. The engine evidently gets a bubble of air, the power
drops off and the fuel pump thinks the engine needs more fuel, the fuel
pumps supplies more fuel, the small bubble of air passes while the engine
gets the fuel and speeds up and the fuel pump then goes back to the proper
setting.
Herb Hoffman
My Tyme
Prairie 29
>Our trawler has developed a surge. ...Running at
>2150 RPM, our normal cruising speed, the Perkins 4-107 sped up to about
>2600 RPM and then immediately went back to 2150. ...This continued
happening but on a more frequent basis and
>then mysteriously went away. ...Once it starts it seems to come each time
more frequently. Subsequently
>any journey of an hour or less produces the surge with increasing
>regularity. ...but I would have thought it would die if fuel starved or
>ingesting air not surge ahead.
