Field Marshall will start but won't keep going

[MattR]

Our series 1 will start quite well and run nicely for 15-20 seconds or so but then stops - I try altering the revs, giving the decompresser a dab etc, but to no avail. On one occasion a couple weeks ago she did keep going and when she does - (including a couple occasions when we towed her to run her off) - she'll run really well, went up the hill in top gear, plenty of power etc. Also will start and run fine when hot.

Can't see it being a fuel issue - have unscrewed the injector and its coming through nicely (injector reconditioned not long ago) and anyway if it was then why would it run at all? It seems to me that she'll run as long as the paper's burning but struggles to keep going after that - to try to get a longer burn I've put a sliver of wood in with the paper a few times recently but no luck with that. My instinct was that it's a compression issue - ie the paper is providing the ignition initially but once its out she's lacking enough compression to achieve ignition? But if that was the case then surely she'd be lacking power when I do get her going, which she doesn't.

Just wondered if anyone could provide any suggestions/thoughts, thanks.

 

[startinghandle]

Whereabouts are you ?
I am not familiar at all with Marshall but I remember a Marshall enthusiast having to tow start his tractor because
of severe engine wear but has passed
away

 

[Ley253]

Our series 1 will start quite well and run nicely for 15-20 seconds or so but then stops - I try altering the revs, giving the decompresser a dab etc, but to no avail. On one occasion a couple weeks ago she did keep going and when she does - (including a couple occasions when we towed her to run her off) - she'll run really well, went up the hill in top gear, plenty of power etc. Also will start and run fine when hot.

Can't see it being a fuel issue - have unscrewed the injector and its coming through nicely (injector reconditioned not long ago) and anyway if it was then why would it run at all? It seems to me that she'll run as long as the paper's burning but struggles to keep going after that - to try to get a longer burn I've put a sliver of wood in with the paper a few times recently but no luck with that. My instinct was that it's a compression issue - ie the paper is providing the ignition initially but once its out she's lacking enough compression to achieve ignition? But if that was the case then surely she'd be lacking power when I do get her going, which she doesn't.

Just wondered if anyone could provide any suggestions/thoughts, thanks.

Compression issue. Unless your taking her out to work on the same job every day, any small loss wont be noticed in the power stakes, and it doesnt need to loose much compression to affect starting.

 

[startinghandle]

What oil are you using?
It's my opinion that old engines run better on single grade oil

 

[Ley253]

If you do delve inside, while your there, clean and check the oil return valve in the crankcase, these can block over the years and lead to oil pooling in the crankcase, the engine then picks this up, and gleefully runs on it, with no speed control! Ours did just that, luckily, without much damage, the vaporiser in the head was crushed as the con rod had stretched enough to allow the piston to hit it! It returned to normal(like our heart rates) when the engine slowed down, a new vaporiser was all that was needed.
This runaway, can also happen after too many failed attempts to start, so beware.
Also, keep an eye out for the "auto Reverse"! If left idling, the engine can reverse, if this happens, its very disconcerting moving off backwards, on engaging first gear!

 

[Hawkes]

You should never tow start a field marshall , it gives dire warnings in the instruction books. I think it is the large straight cut diff crown wheel that is the worry. The safest way is a flat belt off another tractor .
If you have tried giving the decompressor a flick once it starts and it still just wants to stop , then it sounds like loss of crank case compression. It is a two stroke so needs the crankcase to be air tight to expel the exhaust gases and keep running. The oil return valve is one candidate but it is most often the crankshaft air seals. These are large bronze rings with springs holding them against a seat. If they are worn or sticking they will cause the symptoms you describe. If they are the problem when it is running take off the oil filler cap on the transmission and feel for air puffing out ( crank seal on pulley side), also the engine oil filler cap ( crank seal on flywheel side) . Check the reed valves on the air inlet under the air filter too, they crack and bits drop off.

 

[MattR]

Whereabouts are you ?

Cornwall. Very apt username for this thread by the way!

Compression issue. Unless your taking her out to work on the same job every day, any small loss wont be noticed in the power stakes, and it doesnt need to loose much compression to affect starting.

Thanks, that makes sense.

If you do delve inside, while your there, clean and check the oil return valve in the crankcase, these can block over the years and lead to oil pooling in the crankcase, the engine then picks this up, and gleefully runs on it, with no speed control! Ours did just that, luckily, without much damage, the vaporiser in the head was crushed as the con rod had stretched enough to allow the piston to hit it! It returned to normal(like our heart rates) when the engine slowed down, a new vaporiser was all that was needed.
This runaway, can also happen after too many failed attempts to start, so beware.
Also, keep an eye out for the "auto Reverse"! If left idling, the engine can reverse, if this happens, its very disconcerting moving off backwards, on engaging first gear!

Yes I've heard of that happening, not the possible damage though! And yeah I remember father talking about how he had it run backwards once or twice, I think shutting off the revs then opening her up right at the last minute or something.

You should never tow start a field marshall , it gives dire warnings in the instruction books. I think it is the large straight cut diff crown wheel that is the worry. The safest way is a flat belt off another tractor .
If you have tried giving the decompressor a flick once it starts and it still just wants to stop , then it sounds like loss of crank case compression. It is a two stroke so needs the crankcase to be air tight to expel the exhaust gases and keep running. The oil return valve is one candidate but it is most often the crankshaft air seals. These are large bronze rings with springs holding them against a seat. If they are worn or sticking they will cause the symptoms you describe. If they are the problem when it is running take off the oil filler cap on the transmission and feel for air puffing out ( crank seal on pulley side), also the engine oil filler cap ( crank seal on flywheel side) . Check the reed valves on the air inlet under the air filter too, they crack and bits drop off.

Ah. I'll bear that in mind about towing off, didn't know that, thanks. Yes someone did mention about the crank seals, is it quite a job to replace them? I'll do as you suggest re feeling for air puffing out. Yep I've checked the reed valves, they're pretty good I think.

I've heard of people replacing the paper with an electric heater plug - I wondered whether this might work by heating for longer? (Although might spoil the charm of it a bit!)

 

[Ley253]

One other thing, is the exhaust clear, in normal use they used to burn themselves out, as show tractors I doubt they would ever get hot enough, and so would gradually choke themselves.

 

[startinghandle]

I know of someone who has collection
Of Marshall tractors and has rebuilt some of the engines and he knows his
stuff .. before you start he would be good guy to speak to but none of his tractors are for sale

 

[startinghandle]

You should never tow start a field marshall , it gives dire warnings in the instruction books. I think it is the large straight cut diff crown wheel that is the worry. The safest way is a flat belt off another tractor .
If you have tried giving the decompressor a flick once it starts and it still just wants to stop , then it sounds like loss of crank case compression. It is a two stroke so needs the crankcase to be air tight to expel the exhaust gases and keep running. The oil return valve is one candidate but it is most often the crankshaft air seals. These are large bronze rings with springs holding them against a seat. If they are worn or sticking they will cause the symptoms you describe. If they are the problem when it is running take off the oil filler cap on the transmission and feel for air puffing out ( crank seal on pulley side), also the engine oil filler cap ( crank seal on flywheel side) . Check the reed valves on the air inlet under the air filter too, they crack and bits drop off.

I am not in any disputing what you say about not tow starting I could be wrong but I seem to remember reading an article about Marshall in one of the magazines and it said that the tractors were tow started off the production line

 

[Hawkes]

@startinghandle
I think with Marshall maybe it was a case of " do what I say, not what I do" ! I just looked back at some handbooks to check my memory not playing tricks and in the Model M book I have, it says not to do it or serious damage may occur, no more detail though, so exactly what they were worried about I am not sure. I always assumed it was the large straight cut crown wheel to small pinion that might be vulnerable ?

@MattR
The crank seals are a fair job as the whole crankshaft has to come out to replace them. The housings that they run against often need machining flat again as they get scored. They both have an oil feed direct to them which helps.
Here are a couple of photos of a Model M I rebuilt for a chap in the 80's and just did the seals on for him whilst repairing a frost burst block.

 

[fenhayman]

Father had an old well worn Series 1 which I couldn't keep going after it started even after randomly hitting the decompressor. The regular drivers hit the decompressor at a particular time in the firing cycle and kept it running.

 

[Fuzzy]

I would consider draining/cleaning fuel tank, fuel filter and fill with fresh diesel. Possibly decompression valve could be sticking and/or badly pitted? Is it clean and free moving?

 

[TrickyT]

I was surprised as how big the crank and piston were in a Field Marshall.

Regards

Trevor

 

[Rusty_Relics]

My series 1 was like the one in question, wouldn't keep going. I fitted new piston rings and decompressor valve and that seemed to sort it. I shrunk the big end cap and rebored it back round with in the specs on the milling machine. I did post a restoration thread over on the Classic Machinery Network forum in the tractor section.

 

[startinghandle]

My series 1 was like the one in question, wouldn't keep going. I fitted new piston rings and decompressor valve and that seemed to sort it. I shrunk the big end cap and rebored it back round with in the specs on the milling machine. I did post a restoration thread over on the Classic Machinery Network forum in the tractor section.

I have just realised what you mean by shrinking the big end.... new Babbitt bearing

 

[Rusty_Relics]

I have just realised what you mean by shrinking the big end.... new Babbitt bearing

No, I milled .025" or .030" I can't remember exactly. from the bronze end cap. Effectively closing up the diameter and then rebored the lot and it cleaned up nicely. I know this has shortened the stroke ever so slightly but on something as agricultural as a Field Marshall it doesn't really matter. And it saved me a ton of money not having to go to line Mr Crawford's pocket.

Thanks,
Carl Hargreaves

 

[startinghandle]

Reading this again has got me interested in Marshall, I do know of 2
Which are not far away parked up for many years one has a cracked block so possibly a future project providing the price is right which is asking a lot

 

[Ley253]

Having had, and ran a Marshall years ago,they are not the easiest of beasts to show, being a very heavy, solid lump, but they do entertain the public at shows, especially when starting, the handle alone is impressive! On working days, they can be guaranteed to shake both the driver and implement to pieces, and they some times manage to start to self destruct, ours shook its seat loose many times! Their coating the driver with very dirty oil from the exhaust, and the mobile blow torch effect when they burn the exhaust clean is more evidence of their unique character! Would I have another, given the chance?Yes.

 

[OGB]

Reading this again has got me interested in Marshall, I do know of 2
Which are not far away parked up for many years one has a cracked block so possibly a future project providing the price is right which is asking a lot

Me too. Always had a passion for Marshalls. As a young lad i was fascinated by them, they were always something different to the multi cylinder engine variants. Would love a series 2 mark 2, in working clothes, command quite a bit of brass though...