Problem Starting Yanmar 4JH5E

[rmbriggs]

My Yanmar 4JH5E 54 hp has an annoying starting problem. I always use the glow plugs for 15-20 seconds, give some throttle in neutral, and turn the key. The engine immediately starts within a second, moderately rev’ed up due to the throttle, and then dies a second or two later. A second turn of the key for 4-5 seconds - does not start or fire. Sometimes on a third turn for 2-3 seconds it will start but not always. By the fourth turn it always start in 2-3 seconds and runs perfectly even at low idle.

It’s the same in warm or cold weather and even after the engine has been running and then off for 20 or 30 minutes on a warm day.

It dependably starts and runs after the sequence described above but still is annoying. The engine only has about 1800 hours and has been well maintained.

Any thoughts or ideas?

[Lepke]

You have an air leak somewhere in the fuel line. And/or bad valves in the lift pump allowing fuel to go backwards when the pump isn't running. Debris in the fuel can stick to the fuel pump valves and hold them slightly open when stopped.

[tkeithlu]

Amen. Disassemble, clean, look for ragged O rings, cracks in metal tubing, loose connections, and dirt. Consider adding a Racor filter if debris is coming from your fuel tank. Oh. Test that. pour a bunch into a clean dry glass jar and take a look.