3L Runs On/Dieseling and Hesitates between 1,100-1,500RPM

[mpdive]

Re: 3L Runs On/Dieseling and Hesitates between 1,100-1,500RPM

Clean the battery cables. Good place to start. I have chased many ghosts in my life and have found it to be a simple battery connection. Good Job Mate. (I may start using that tag line........Makes me feel like a Foster's.....

 

[kidafa]

Re: 3L Runs On/Dieseling and Hesitates between 1,100-1,500RPM

UPDATE

Had the boat out today now I've reduced the idle and richened the idle speed mixture. No longer runs on at all and starts very easily.

All I need to do know is sort out the slight hesitation it has and work out how to reseal the drain which appears to be leaking water in.... Boat took on a bit of water over the day and when I got home I filled the bilge with 2 buckets of water and I could see water leaking ever so slowly from around the metal piece that the bung threads into. Should I just undo those three screws remove it and clean up the fibreglass and metal piece and then re-seal it? What sealant should I used?

Also what tools do you guys keep on board for when you are out?


This is where its leaking from I believe

 

[a1akeywest]

Re: 3L Runs On/Dieseling and Hesitates between 1,100-1,500RPM

that sealant certanly looks like it needs to be replaced.... any marine grade sealant will work,,,

 

[NetDoc]

Re: 3L Runs On/Dieseling and Hesitates between 1,100-1,500RPM

Dieseling is caused by a higher than normal rpm on a HOT running engine. No, I don't mean the engine is overheating, though that can exacerbate the situation. I am referring to combustion temps. Typically, hotter than normal combustion temps are caused by timing that is too high or an engine that is running too lean. A rattle on acceleration (ping) is a dead give away on this but its not the final word. From the sound of it, I would check for any vacuum leaks and then the float level in your carburetor. Carbs are creatures of vacuum and any interruption of that creates a lean running situation. Also, a heavy float or one that is set too low in the bowl, will cause a lean condition and that would also account for that lag. When you "goose" the throttle, you are allowing the accelerator pump to overcome the momentary leanness, masking the issue. Check you timing while you're in there. On a car, an EGR valve is used to help reduce combustion temperatures.

 

[Don S]

Re: 3L Runs On/Dieseling and Hesitates between 1,100-1,500RPM

NetDoc, you probably should have read his last reply in this thread. He fixed the dieseling by reducing the idle and adjusting the idle mixture.

 

[NetDoc]

Re: 3L Runs On/Dieseling and Hesitates between 1,100-1,500RPM

NetDoc, you probably should have read his last reply in this thread. He fixed the dieseling by reducing the idle and adjusting the idle mixture.

Don, I read it. I think he only fixed half the problem. There are TONS of half fixes out there that have been tried on automotive and boat engines for decades. Hotter combustion temps burn a lot cleaner, so manufacturers have been getting them close to max since the 1960s. Given the fact that he HAD dieseling and the fact that he still has mid throttle hesitation, it sounds that he still has a lean mix problem. That's either a vacuum leak or a low/heavy carb float issue. Of course, that could also be caused by inadequate fuel getting to the carburetor. Further testing/inspection is essential.

Combustion heat is a real killer of engines. It's bad on cylinders, valves and can even crack a head. Dieseling means that the temps in the combustion chamber are hot enough to keep a gas engine running WITHOUT the need of a spark plug. Having the engine run on a few moment is a symptom of something far worse. Indeed, that can be a bit embarrassing, but it won't actually hurt your engine. However, the mechanism behind that dieseling is damaging and steps should be taken to reduce that heat.