14 Jan What’s Wrong with the Diesel?
I’ve written before about how our diesel died on the way south from Ft. Myers (December 2014) and how we’re having to rebuild the engine (read about the trip here; the decision to rebuild the engine here). I’ve had a lot of questions about what we’ve found in the course of the rebuild and what the problem seems to be. In short, what caused this?
A few background facts:
- We bought the boat last April with 350 hours on the engine, a Westerbeke 30B.
- The boat had been repowered in 2010 by a previous owner — not the one we bought the boat from. We do not know why it was repowered at that time, when the boat was just 11 years old.
- The survey indicated no problems with the engine. Due to the young age and low hours on the engine, we did not have a separate engine survey.
Our trip before the engine died:
- When we put the boat in the water after being in storage for the summer, the engine fired right up with no problem.
- The engine ran well except for a couple of times when we lost RPMs briefly — we thought this was due to bad fuel and changed the fuel filters.
- We motored about 40 hours over 8 days.
- The engine made no strange sounds and was not smoking.
- The engine did not overheat and oil pressure was good.
- The engine was running just 12 hours before it refused to start.
A compression test showed very low compression in all three cylinders (it should be 398 psi in each; it was 200 in one and just under 100 in the other two). What we’ve learned since:
- There is absolutely no sign of salt water intrusion anywhere from the exhaust system.
- Two injectors were bad.
- All valves were carbonned up badly and not seating (closing) properly.
- All piston rings were stuck badly — carbon, not rust.
- No noticeable wear on cylinder walls.
- The engine is very clean.
We’ve had three different mechanics look at the engine and consulted with several others via phone and email.
The consensus is that this shouldn’t happen to an engine this new and with this few hours.
But it has and so the second consensus is that the most logical explanation is that the injectors being bad put a lot of extra fuel in the cylinders, which caused the valves and rings to carbon up. Apparently this had been going on for some time, and the day the engine wouldn’t start was just a case of “the last straw.”
Yes, it seems more likely that the engine just wouldn’t have started after being stored for the summer if it was carbonned up. And that the bad injectors would have made it run rough before it died. But it ran well just 12 hours before it wouldn’t start. And that’s another reason why everyone is so puzzled.