Engine runs only at low RPM

[FPW501]

Hi guys!
Now I need good advice from someone with greater experience again!

I have assembled a Fordson major diesel (year model 52-53 with an injection pump with vacuum regulator.) I have assembled it from parts of a one engine with a broken engine block and another with a block in good condition. Otherwise, valves have been re-faced and worn parts as piston rings etc. has been replaced to get an engine in decent condition, even if it is not to be seen as being refurbished to "new condition". (The injection pump and the cylinder head are both from the engine with the cracks in the block. It run well until I took it apart but the coolant was leaking badly. It also showed to have crakes between three cylinders! )

Now to my problem. The engine starts up but runs at very low speeds. The rpm is approximately about 500 rpm. In other words, lower than normal idling speed. At this low engine speed the engine runs unevenly. The rpm is not affected by the damper in the intake pipe. In other words, it is not possible to rev it up in a normal way.

As a step in the troubleshooting process, I removed the lid of the injection pump control lever. (I have also checked that the vacuum pipes are mounted in correct places on the intake manifold and regulator.) When I force the control rod in the injection pump backward to give more injected fuel, the engine speed rises and the engine runs well.

In other words, the problem is in the governor’s function. It appears to be a too big under pressure / vacuum in the governor. It is needed a relatively high force push the control lever backwards to increase the fuel/rpms. The power of the spring in the governor feels normal. However, I have not done a serious test of it but it feels reasonable. Additionally, the engine do not have the oil bath air cleaner installed. Instead, it has a simpler filter mounted as it is only a test start. The engine is not mounted in a tractor yet.

Have anyone had the same problem or any ideas of what causing it?

Best regards! Martin

[AdrianNPMajor]

Have you checked the diaphragm? There is often a split lurking in one of the folds.
Re the cracks between the cylinders, this is due to the tractor being operated with low coolant levels or no coolant. The pistons expand and seize, causing the cracks you describe.
This is not a problem. The head gasket puts a lid on and seals the cracks, so there is no leakage of coolant. And there is no significant weakness introduced into the block - the head when bolted down holds everything together.
Good luck.
Best, Adrian.

[AdrianNPMajor]

ps When I say it's no problem in the answer above, I'm assuming the liners and pistons have been replaced since the engine seized. I meant the cracks in themselves are not a problem.
Best, Adrian.

[FPW501]

Hi!
I have checked the diagram and it is OK. I had some time this afternoon and could do some more test. When I loosen the nut in the front of the governor the engine start to perform more or less OK. ( The dumping valve adjuster ) But as soon i tighten it the problem comes back. When it is loos there is a obvious leak for air in to the governor reducing the vacuum. I think my next step will be to check the vacuum pipes for obstacles stopping the airflow.

Or do you have any other suggestion?

Regarding the block; The cracks in the block are most likely not caused from the engine seizing. From the beginning this engine was a kerosene engine. It was later rebuild/changed to run as diesel, and was used for some 10 -20 years. The liners were kept and was in rather good shape when I took it apart. ( I changed them now anyway ) The internal cracks was as you write not a problem. But at the left front corner of the block there was a big and slowly growing crack causing coolant leaks.

Best reg. M

[shepp]

The fact that you hear air being drawn into the governor housing when you release the adjusting nut suggests that the vacuum pipes are clear and the housing is being subject to vacuum when the engine is running. When the adjusting nut is slackened, which allows the adjusting screw and it's internal bush to move slightly off line, you say the governor performs as it should.
This suggests that the damping valve piston might be sticking in the bush in the adjusting screw when the locking nut is tight, which prevents the piston and diaphragm assembly from moving and operating the rack. You will have to take the governor housing off, remove the snap ring and retaining plate, and withdraw the diaphragm and piston assembly and spring. Unscrew the adjusting nut and screw with it's internal bush from the housing. Thoroughly clean everything up, check the damping piston is free to move in the internal bush in the adjusting screw.
*** The damping piston has a small ball joint where it screws into the diaphragm plate which allows the piston to self centre itself in the bush in order to allow it to move freely - check that this ball joint is free and lightly lubricate it with oil before re- assembly ***.
Whilst everything is out re-affirm that the diaphragm is sound. Re-assemble and if everything is OK re-set the damping valve to eliminate any surging.

[AdrianNPMajor]

Re the cracks between the cylinders, this is what I found a few years back on my 1954 Diesel Major. I know that the engine had been run without coolant. After a rebuild the engine ran like a Swiss watch.
I'm interested to know more about the other crack you mention. Just wondering how this came about. I don't know how the vapourising oil/diesel/petrol blocks differed in construction, but off the top of my head I cannot think of a scenario other than low or no coolant over-heating of how a block could crack where you describe, though I accept, of course, that it has.
Best, Adrian.

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[FPW501]

Hi!
The other crack is some 5-8 centimetres long and vertical. It is located at the front left corner of the block. ( Behind the generator, above the coolant tap ) It is not really uncommon on earlier E1A blocks here in Scandinavia. The later blocks used for Super majors have a bit more material at this area. The corner is a bit more “sharp” The older ones are more rounded.

I think this kind of cracks could be caused by freezing. From what I heard it was common to use pure water without antifreeze in tractors used only in summertime. The problem is that here in Sweden we can occasionally have temperatures below zero some night 8-9 months of the year. So it is easy to by mistake have water in the block a frosty night! The lack of antifreeze and frequent emptying of the system, letting air in, also promote rust that maybe weakens this area of the block.

Best reg.

[AdrianNPMajor]

Apologies. I thought the crack in question was on the top surface of the block.
Do you know any good welders? I believe it is possible to repair a crack such as you describe, given that it does not affect the structural integrity of the block. Ford used to weld castings in the factory to repair casting defects. Alternatively, there is probably a sealing compound that would do the job.
Best, Adrian.