Fuel pump leak

[Tom of Salt Lake]

I have an 84H34 with a Yanmar 3GMF engine. When the engine is running, diesel fuel seeps from the mount between the mechanical fuel pump and the engine and collects in the engine bilge. The fuel lines in and out of the pump seem dry (not leaking). The fuel delivery system looks something like this:Fuel tank --- electric pump –- 1st Racor –- 2nd Racor –- mechanical pump -– fuel filter -–I don’t normally run the electric pump because, until recently, the engine runs without it and the leak is worse when the electric pump is turned on. I will clean the Racor’s and verify that I can run without the electric pump.My questions are:1)To stop the leak is it necessary to replace the mechanical fuel pump?2)Do mechanical fuel pumps become weak (less efficient) with age?Any help will be appreciated.Thanks,Tom

 

[John K Kudera]

You should replace it

There is a possibility that the fuel is not only leaking on the outside, it may be leaking thru the pump to the inside, and into the oil system. Don't risk that,If you cannot change the pump, by pass the mechanical pump and use the electric. I have run a short piece of fuel hose from inlet to outlet on the mechanical pump to avoid fluid loss and mess.

 

[Bill O'Donovan]

Kudos to Kudera

You should indeed replace the fuel pump. Chances are the banjo fitting has been tightened one too many times and has stripped the alumnimum threads, (which is all too easy to do with the torque of a child).

 

[Andy Howard]

Check the compression washers first

Bill and Kudera are probably right but I would check the copper compression washers at the pump first. They should not be reused and are the source of a lot of small diesel fuel leaks.

 

[Tom]

Installed a new pump

I installed a new Yanmar fuel pump and gasket this weekend and the fuel leak has stopped! The bad news is I now have an oil leak because the one of the two bolts that attaches the pump to the engine will not tighten sufficiently. The bolts are different lengths for some reason and I don’t know if it maters so I used the shorter bolt (the one that tightens okay) on the side of the pump closest to the back of the engine. Hopefully I will be able to stop the leak without major surgery.Tom