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Author Topic: ST3 genny overheated, fuel in CC  (Read 327 times)

macguyverkevin

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ST3 genny overheated, fuel in CC
« on: September 06, 2023, 05:44:15 PM »
Hello all you wonderful Lister gurus!

Regarding my 1976 Lister ST3/Kohler 12Kw enclosed trailer-mount gen unit.
Our local PoCo was out replacing a pole yesterday so I fired up the ol' genny and ran the house during the work.
Started fine, ran smooth, never even winked at the load, so I went about doing my thing. After about 2-2.5 hrs, it shut down! Overheat switch closed and opened the safety relay. Engine was REALLY hot! This morning, I checked the oil and found it to be WAAAAYYY overfilled and diluted with fuel. When it failed, it was a cool day and the load on the system was very light.

Not sure where to begin diagnosing, is there anything I should be looking at? I suspect possibly the mechanical fuel pump may be a source of the dilution, and I hope I didn't smoke the cylinders with the poor lube!! Tried starting it after a couple hours of cool down, but it wouldn't crank, tried to, moved some. This model uses the gen as the starter, it tripped the Klixon overload protector!

Thanks in advance, as I know there will be lot's of good advice coming my way, y'all ROCK out there!!
Tinkerer of all things mechanical!
It's all nuts and bolts and amps and volts!

ajaffa1

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Re: ST3 genny overheated, fuel in CC
« Reply #1 on: September 06, 2023, 11:11:04 PM »
Hi Macguyverkevin, looks like you have some serious problems, I do hope you have not fried the pistons. They are aluminium and will seize without sufficient lubrication. You are going to have to dismantle to asses the damage if it has not freed up as it cooled down.
I doubt the problem was caused by external the fuel lift pump, these are a diaphragm pump and if the diaphragm perforates they do not pump any fuel and the generator would not start but check it anyway.
Much more likely to be an internal fuel leak, if you remove the crankcase door you will be able to see the three fuel injector pumps. Each pump has a banjo bolt connected to the low pressure fuel inlet pipe, check each of these for leaks. Each pump has a high pressure pipe coming out of the top, check each of these for leaks.
Remove the three rocker covers, you will now be able to see the fuel injectors, each of these has a high pressure fuel pipe connected to it. check these for leaks.
Let us know what you find, good luck.

Bob

macguyverkevin

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Re: ST3 genny overheated, fuel in CC
« Reply #2 on: September 07, 2023, 07:46:40 PM »
SOLVED (partially)

Well, I opened her up some, took the side panel off the engine and inspected the injector fittings and banjo bolts. No obvious fuel leakage there. Cranked her up and VOILA! she started! So far, so good. No fuel leakage showed up during running either. didn't run it for any more than 15 sec.
Next, I pulled the mechanical fuel lift pump, reinstalled the hard line and actuated it manually.... fuel ran out of the rocker arm port like crazy!

So I found the source of oil dilution, now I think I will just delete the OE mechanical fuel pump and run a common outboard electric lift pump.

My rule is: When restoring old equipment for practicality, always look for opportunities to improve on what was originally the standard; this isn't a show piece.

Now to assess the engine post-failure.... need to see how to do a compression test on one of these?
Tinkerer of all things mechanical!
It's all nuts and bolts and amps and volts!