Ransomes MG6 Drayton Diesel – Running Problems

[dieseljd]

Hi,
After too many years sat at the back of the barn, I have been giving the Ransomes MG6 (Actually an ITC) a spring clean. The diesel Drayton 34R engine was overhauled 15 years ago but has never run properly and I would love to finally get it to a usable state.

The engine will fire easily but only run flat out and as soon as the excess fuel plunger pops back in the engine dies. It just wont idle.

Known good areas: Excellent compression, rings, bore and valve reworked. Crankcase Flapper valve looks good. Clean oil and filter, oil galleries clear and lubrication look good.
Injector gives excellent fine mist. Pump was checked by a local diesel company 15 years ago.

Possible issue areas:
>Governer moves and link is set to 72mm but I dont know if the actual governor is correctly set.
>I should re-check the injection spill timing but it visualy looked pretty good.
>Moving the rack on the diesel pump clearly turns the fuel on/off to the injector but the rack does feel a little floppy and I dont know how much movment I should see for different metering quanitities.

I’m guessing its either something in the Governor springs settings or the pump is not metering correctly.
Anyone with experiance with 34R engines got any thoughts?
Thanks, John.

[wristpin]

An uninformed guess, check for air leaks.

[dieseljd]

Thanks, that is a valid point. Being two stroke, it uses the crankcase pressure as part of the cycle and maybe I should double check the flapper valve. There must also be a link between the rear crank chamber and the front gearpump chamber for oil movement.

I have double checked the fuel pump ‘spill angle’ It was at 25 degrees BTDC, now adjusted to the required 30 degrees BTDC.
Tappet adjusted to correct 6 thou. Decompression ‘fork’ needed a tweak and now works as required with the new tapped adjustment.

Will try for another start this eve and see what we can find. J.

[expeatfarmer]

Try removing the fuel injector and reconnect it outside the engine,crank the engine with various throttle settings and watch the mist see what happens when you shut the throttle down, sounds as if the governor fuel rack link may be set wrongly. Good luck.

[dieseljd]

Excellent idea…I’ll try that as soon as I can get another pair of hands on the crank.

[dieseljd]

For anyone travelling the same path…

Tested injector out of the cylinder and achieved a good fine mist, with what appears to be a fair level of control as the rack is gently moved…a few mm make a notable difference.

I placed a tie-wrap around the governor bob weights, re-assembled and fired up. We could then play with the throttle and rack without the governor adding constant adjustment. An ‘interesting’ and somewhat risky stratergy but we managed to get a fair level of ‘manual’ control but could only get a lowest rpm of around 1100. At least we now believe the injector and pump to be functioning.

It was noted that the bushing around the ‘excess’ fuel plunger was wound a fair way in. The internal end of the plunger is tapered, the throttle rests against the plunger when it is fully home.
Due this taper, by adjusting the bushing and the plunger depth, you can adjust the maximum throttle and max fuel for normal running.
I had to wind the bushing out..or else the throttle would always be pushed to far back and the engine would stop.

There is also a link between the throttle linkage and the rack. The length of this determines the sweep of the rack in relation to the throttle. Whilst an end to end length of 72mm for the link has been tried…I finally found a much shorter length of 70mm allowed my throttle and governor assemble to sweep the fuel pumps rack across what seems to be the correct range. Through Cut-off –> low fuel –> full fuel –> excess fuel positions.
(given basic no load testing so far).

I spun the governor up with a drill and noted the inconsistant bob weight behaviour. I was fully stripped down and cleaned. It now operates far more smoothly. With the governor and housing assembled, a spring balance can be placed on the ball of the throttle arm. Pulling past the governor, a force of around 0.7Kg was needed for the slightest movement of the bob weights and 1.8 to 2 KG of force for the bob weights to be pulled fully out.
This is just a ‘hobby’ method of measuring the bob springs and setting my starting point.

In practice the springs were adjusted a turn at a time, governeor fitted and engine started. This was repeated many times to find a good overall setting to give an idle of roughly 700RPM and a fast running around 2000.

Also, there is the access plug allowing the linkage to the popped on-off the throttle arm, if this is left off during engine running. Given a constant throttle possition you can observe how much the governor is driving the fueling, its not easy to explain but worth observing as you are trying to characterise the systems behaviour during run-ups.

I doubt the settings are ideal but until I sort the clutch and get some load on it…its a good starting point.
Highly unlikley its the end of this process but its a darn good start. 🙂

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