Nuffield 4DM

[DCR]

Hello

I have a Nuffield 4DM, that i have recently purchased, and it seems like its had a series of bodges done to it over the years, and very little work mechanically, resulting in lots of wear. I am slowly going through it, I have done the brakes, unseized lots of linkages, rebuilt the hydraulic system, worked on the wiring, put a new exhaust manifold on, lots of other new bits, and I have recently started overhauling the steering.

Anyway, my question, it will not start on its own. I have made a thermostart system, simmilar to the Perkins system, which i guess will help, as she will start fine with a little warmth from a blow torch or a hot air gun.

Now i have a Simms pump, and i have a cold start, excess fuel button. On our David Brown, if its cold weather she will not start at times, so i put the excess fuel 9n and what a difference, fires straight up. When i activate it on the nuffield, it makes absolouteley no change what so ever. I find this slightly odd, what do people think?

I have a compression tester, which i plan to use at the weekend, but any other advice on what could be happening would be greatly apriciated.

I have thought of doing work on the engine, but i have to limit what i am spending on the tractor as i have orther projects too.

Thanks in advance

David

 

[agrimax]

Is the excess button actually pushing in and staying in? I assume you know to open the throttle fully before pushing it? My Nuffield,which has a 4/98 lorry engine in but will be the same set up,is hard to start in cold weather without the button in,but starts instantly with it pressed.
Pull the cover off the side of the pump and see if the rack is moving fully(can't remember which direction) when the button is pressed with the throttle open.If it is,then close the throttle to see if the rack jumps back again.Those BMC engines were known to be easy starters.

 

[DCR]

Hello

Thanks, i didnt know the throttle needed to be wide open no, i will try tomorrow and report back.

Hopefully that makes a difference.

Thanks

David

 

[agrimax]

........Hopefully..

 

[phil t]

As above pull throttle wide open and then press cold start you should feel it kick in

 

[DCR]

Well, i looked and tried what you said, but i found the throttle had no difference. My throttle works on the air inlet, on the butterfly valve. How does the pump know when to increase fuel? I am more used to the throttle being linked directly to the pump.

Is it sensed via vacuum or some such? I cant see how.

Cheers

Dave

 

[agrimax]

Ah.......Forgot about the early set up. Yes,it's vacuum contolled throttling on these. With the stop lever in run position,will the button press in and stay in? It may not be doing it's job internally.

 

[Ley253]

For the cold start to operate, the stop must be in, as well as the throttle open.Button should go in, and stay in until the engine starts.take the cover of the pump, and check that the rack moves forward when the button is pressed, and while your there drain and fill the pump with new oil.