1994 vintage Yanmar 2GM20F. Well maintained by previous owner. Yard has been doing annual oil change and winterizing. Worked fine for 4 years without a single problem.
In last 10 days, we did a NE cruise with about 20 hours of motoring over several days at 2000 rpm.
Here is full description in case timeline is important. Fuel tank is metal and 17 gal.
End of season 2020 - filled with diesel with stabilizer, oil change, winterizing
Start of season - no problem with starting
April-May - multiple day sails with about 20 hours of motoring total, no problem.
Trip
Day 0 = bled the fuel/water separator, refilled with new fuel, could not start the engine until I hit the solenoid with a hammer! Replacement starter on order. Started multiple times, no issue.
Day 1 = 8 hours of motoring, 2k rpm - no issue.
Day 2 = 2 hours of motoring - no issue
Day 5 = 6 hours of motoring - no issue
Day 6 = added 3 gallons of diesel, vintage June 2021
Day 8 = 2 hours of motoring, no issue
Day 10 = 6 hours of motoring, 2k rpm. After 6 hours, engine started to oscillate slightly in speed, as if the throttle was being pulled back and forth. Like a sine wave almost. Pattern would come and go. Wind picked up so we put up the sails, keeping the engine at idle. Out of nowhere, the pattern intensified and the engine stopped, with no response when moving the throttle, as if the fuel stopped flowing. We let the engine cool till we got close to our yard. With insurance card in hand, we cranked engine which started first time but RPM very erratic, we babied the throttle back and forth, seemingly with no effect at first until the engine revved UP as we throttled down. Brief puff of white smoke and then all was well, we motored into our berth and the rpm seemed very stable, albeit with a cooler engine. It was as if the engine burped...
So I am starting to do prepare a plan of attack. I am not sure about the root cause. My thoughts so far:
0- Replace the starter but unrelated to issue at hand
1- Water in fuel - I have Raccor separator so unlikely
2- Dirty fuel - I will change both primary and secondary filters
3- Air in fuel line - no obvious leaks but I will bleed when I change the 2 filters.
Are there any other possible root causes that would cause this intermittent failure? Injectors were taken apart and cleaned 6 years ago. I checked the throttle cable - no issue, same with shutoff cable, no issue.
As always, help appreciated.
In last 10 days, we did a NE cruise with about 20 hours of motoring over several days at 2000 rpm.
Here is full description in case timeline is important. Fuel tank is metal and 17 gal.
End of season 2020 - filled with diesel with stabilizer, oil change, winterizing
Start of season - no problem with starting
April-May - multiple day sails with about 20 hours of motoring total, no problem.
Trip
Day 0 = bled the fuel/water separator, refilled with new fuel, could not start the engine until I hit the solenoid with a hammer! Replacement starter on order. Started multiple times, no issue.
Day 1 = 8 hours of motoring, 2k rpm - no issue.
Day 2 = 2 hours of motoring - no issue
Day 5 = 6 hours of motoring - no issue
Day 6 = added 3 gallons of diesel, vintage June 2021
Day 8 = 2 hours of motoring, no issue
Day 10 = 6 hours of motoring, 2k rpm. After 6 hours, engine started to oscillate slightly in speed, as if the throttle was being pulled back and forth. Like a sine wave almost. Pattern would come and go. Wind picked up so we put up the sails, keeping the engine at idle. Out of nowhere, the pattern intensified and the engine stopped, with no response when moving the throttle, as if the fuel stopped flowing. We let the engine cool till we got close to our yard. With insurance card in hand, we cranked engine which started first time but RPM very erratic, we babied the throttle back and forth, seemingly with no effect at first until the engine revved UP as we throttled down. Brief puff of white smoke and then all was well, we motored into our berth and the rpm seemed very stable, albeit with a cooler engine. It was as if the engine burped...
So I am starting to do prepare a plan of attack. I am not sure about the root cause. My thoughts so far:
0- Replace the starter but unrelated to issue at hand
1- Water in fuel - I have Raccor separator so unlikely
2- Dirty fuel - I will change both primary and secondary filters
3- Air in fuel line - no obvious leaks but I will bleed when I change the 2 filters.
Are there any other possible root causes that would cause this intermittent failure? Injectors were taken apart and cleaned 6 years ago. I checked the throttle cable - no issue, same with shutoff cable, no issue.
As always, help appreciated.