Hard Starting Yanmar

[Mark Mowery]

Even though the previous owner had just had the engine rebuilt the year before I bought my H33, the Yanmar 2QM15 was hard starting from day one, especially when temps got below about 50 degrees. Here's two things I did:1. The instructor at a diesel maintenance class I attended recommended I move the fuel return line from the top of the secondary filter housing to the fuel tank. Supposedly the constant dribble of fuel returning back to the filter housing introduces small amounts of air into the system, which could lead to hard starting. He also claimed that this was a characteristic of that particular engine. Hhmmm, maybe. Doing this helped the problem somewhat, but didn't eliminate it completely.2. Discovered there was zero clearance between the valve stems and the rocker arms. After adjusting them to .020" as specified in the service manual, the old (20 yrs.) gal's been starting great ever since. I suppose the exhaust valves weren't closing completely, leading to compression loss?I'd be interested in comments from the diesel mechanics in the group.

 

[Gordon Torresen]

Hard starting 2QM15

Valve adjustment is always important and, from your personal experience, can affect cold starting. We find too, that injection timing is important, more so for the Q series than other Yanmars.  The speed with which the starter motor spins is also very important. The faster the air can be compressed, the less can blow by the piston, resulting in higher compression temperatures.  Good quality diesel fuel contributes to faster starts. A product like Amoco Premier Diesel Fuel is about as good as it gets. You can't take a lesser fuel and dump additives in it to make it better.