[C320-list] Trouble starting Yanmar 3GM

[Jack Brennan]

Losing prime on a diesel like that often comes from a pinhole leak. They are maddening to trace.

It follows that if you do have a leak, there is fuel getting out somewhere to allow air into the system. The first step should be to examine the fuel system from the tank to the injectors, looking for signs of diesel.

The fuel line from the tank to the Racor is downhill, so that shouldn't be causing you to lose prime. The Racor and the lift pump should be suspects. As should the fuel lines where the hose clamps bite into them.

Once fuel gets to the engine, the connectors change from clamps to those pressure fittings that are sealed with copper washers. Those are potential problems. You also have a potential leak spot at the bleed screw on the secondary filter, which is also sealed with a copper washer.

I hated the OEM Racor, so I replaced it with a Racor 500 that I bolted into the bulkhead that separates the aft cabin from the port stern locker. It's easily visible just by lifting the lid on the locker. It's installed at the same height as the fitting on the tank where the fuel exits so it doesn't have to run uphill.

Changing filters is easy, unlike the OEM, once you fit yourself into the locker.

I also changed all of the fuel lines and clamps leading up to the engine. I bought some copper washers from the Yanmar dealer and also changed them. Buy a bunch of them. You can't have too many.

A surprise benefit came when my manual lift pump died. With the Racor 500 higher up, the fuel kept flowing even when the pump wasn't working. I couldn't go very fast, but I got into my slip.

Good luck.

Jack Brennan
Sonas, 1998 Catalina 320
Tierra Verde, Fl.



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