Monday, August 18, 2014

Escalation in Problem Solving

Recently, the generator onboard Eolian began acting up.

First, there has been the smell of diesel present under the floorboards whenever it has been run.  This started small and grew so gradually that I had been ignoring it.  Jane however is the ever-practical one.  "Why does the generator smell like diesel?" she asked, pointing out that there was indeed an elephant in the room, and leaving me no more room to pretend that there was nothing amiss.

I searched all the diesel connections and didn't find any leaks.  Finally, I put it down to a possible fine mist escaping from a high pressure line feeding one of the injectors - it's hot up there and any leaked diesel would quickly evaporate.  Yeah, that's the ticket. 

But the smell persisted. 

And then the generator began to act like it was starving for fuel.  So as an experiment I turned on the electric fuel pump and pressurized the diesel feed line to the generator.  It immediately smoothed out and ran normally.  No problemo!  All I have to do now is run the fuel pump whenever I run  the generator.  And the bilge blower to get rid of those diesel fumes.

Some of you probably have this figured it out by now...

OK, at this point I have grudgingly admitted that there is something actually wrong.  So I took the simplest and cheapest approach as a first step:  I changed the generator fuel filter.  As a problem-solving method, this is a good first step.  It cost very little, was very little effort, and in even the worst possible case, it does no harm.

Unfortunately, it didn't fix the problem.

Next step:  Change the fuel lift pump on the generator.  Cost $75 (yeah, that's a lot for a fuel pump, but then this is a Yanmar 2GM).  As to effort, well there is a reason this was the second thing I tried.  The lift pump is cam-driven, just like a fuel pump on a car, and is located on the port side of the generator, about 3" away from the port battery bank.  Just about enough room to get a socket on the 2 bolts attaching it to the block.  But not enough room to get my head in there to actually see the bolts.  Oh and did I mention that the pump was a corroded mass so ugly that it was difficult to identify except that the fuel lines ran to it and from it?  Apparently the Previous Owner had had a water leak from the exhaust elbow, which is immediately above the pump.  But this also meant that changing the pump not only did no harm, but was a huge positive, regardless if it was the cause of the problem.

Putting the new pump in was an even bigger puzzle because the hard line on its discharge must be installed before the pump is placed and it must be threaded thru some obstacles before the pump can be placed into position.  And all of this must be done while maintaining the gasket in place (I used Permatex to glue it to the lift pump) and fiddling the mounting bolts into their holes, blind.

Yup, that fixed it.  Both problems.  Although invisible under the mass of corrosion, apparently the pump casing had corroded thru or cracked, allowing diesel to escape on the pressure stroke and air to be sucked in on the suction stroke.

This was a classic case of following my troubleshooting aphorism: 

"Do the simple, lowest cost things first." 



Anonymous said...

It's great to find the solution to a problem like that. And so gratifying to confirm once again that 90 percent of diesel engine problems are fuel related, and therefore reasonably easy to isolate. Also nice that you didn't have to "share" this experience with a diesel mechanic!


Robert Salnick said...

Thanks Rick -

I try not to share that kind of stuff

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