Spark plugs fouling on Massey Ferguson MF 35 petrol gasoline 87mm Standard engine

[Mcdust]

When you tune up make sure you are getting qualty components with copper or brass contacts NOT aluminum.

 

[Jerry/MT]

Hi,

I believe the mixture was rich, as it would start on cool mornings 10C/50F without choke. I adjusted and now need the choke. I don't have a tailpipe sniffer to check for over rich, I just do it by nose, which is challenging with a misfire as there's unburned fuel from the misfires. Certainly can't adjust the mix and resolve the misfire as I tried.
Timing checked and set with a timing light. Haven't done dwell.and not sure I have the device.
Water temp rises to 60C/140F in 5 minutes of light work, so I think that's good.
I'll replace the troublesome leads and then try hotter plugs and I haven't replaced the condenser.

Should probably add, I get fat blue white sparks at a plug removed from the cylinder and earthed so I can watch it. 1

Fat blue-white spark is what you want so that implies your points are set correctly. !40 coolant temperature sounds low to me. It should be up around 180F. The hotter plugs will have a longer insulator at the firing tip but they won't stick any further into the cylinder. I think you'll solve your problem with the hotter plug. By the way make sure that you don't have a manifold leak that can locally lean out a cylinder. Another factor is worn distributor bushings. The bushings have tight limits (0.001"-0.002") and if they are worn then the dwell and timing can fluctuate.

 

[Jerry/MT]

A longer reach will usually be a "hotter" plug,
you certainly do NOT want a plug with longer threads.
Threads that go into the combustion chamber are carbon catching glow plugs that will be difficult to remove.

Hotter plugs have longer insulators at the firing tip not longer reach. The cooling path for the firing tip is through the ceramic that surrounds the tip so the longer the insulator the hotter the tip.

 

[Jerry/MT]

Different spark plugs have different lengths which gets the spark closer to the top of the piston, resulting in a much cleaner burn during combustion. Check to see if the plugs are what was initially called for that particular engine. Some have a couple of different options. Maybe carefully check by measuring to see how much room you have when a piston is a top dead center. You might be able to put a hotter plug in with a longer reach into the combustion area on top of the piston.

The insulator that the firing tip protrudes through controls the tip temperature. The tip will be in the same position but the insulator will be located closer to the tip for the hotter plug.

 

[zzvyb6]

172 deg thermostat seems low. Look for a 200 to evaluate whether temperature is the culprit.

 

[FordnMassey]

Fat blue-white spark is what you want so that implies your points are set correctly. !40 coolant temperature sounds low to me. It should be up around 180F. The hotter plugs will have a longer insulator at the firing tip but they won't stick any further into the cylinder. I think you'll solve your problem with the hotter plug. By the way make sure that you don't have a manifold leak that can locally lean out a cylinder. Another factor is worn distributor bushings. The bushings have tight limits (0.001"-0.002") and if they are worn then the dwell and timing can fluctuate.

Hi,
I thought 140F was a little cool too, but that's where it sits with a 180F thermostat in. I'll use a thermometer to check the gauge is reporting correctly and then cover some radiator if needed.

Manifold gasket leak is a possibility. I haven't tested or changed it out. I'll add that to my list. I did reseal the rocker cover ventilation pipe and replaced the rocker cover gasket. The ventilation pipe is directed into the inlet manifold, so leaks there affect mixture on all cylinders.

Distributor bush and bearing were very bad and I replaced the top bearing about a year ago. I couldn't buy the bottom bush and would need to machine one, so I left it. Timing light showed a reduction in variation of timing from 12 degrees to 2 degrees, which in my experience is pretty normal (correct me if I'm wrong).

 

[FordnMassey]

172 deg thermostat seems low. Look for a 200 to evaluate whether temperature is the culprit.

Hi,
Being in a warm climate, daily max 70-110F, the thermostats available are 140F or 172F to avoid overheating. Ive not seen a 200 available. I'll use other methods to heat up the motor if other solutions fail, like covering part of the radiator.
Thanks

 

[jgmo]

Hi,

I have a misfiring and spark plug fouling issue on my 1962 MF35 with the Standard Motor Co 87mm petrol (gasoline) engine. Please note this is not the Continental engine in the US market, but the UK petrol offering. The misfire is most noticeable at light load and nearly entirely stops when loaded/working at 1600 rpm. The plugs, NGK B6S, foul to the point of arcing down the insulator (in the combustion chamber, not the external insulator) causing them to fail to work. This has occurred on 2 cylinders and it is part, or possibly all, of the misfiring issue I have. The motor burns minimal to no oil, has suitable compression across all 4 cylinders. The tractor does around 5 short runs of light work each week, which do bring it to 60C (140F), but it only "works hard" around twice a year. Fuel is 91 octane and due to recent supply changes locally, I am hearing reports it burns dirty. I use a valve protection additive.

Questions:
1). anyone got a suggestion for resolving this plug fouling issue?
2). Would a "hotter" plug help burn the build up off the nose?
3). what eople using in this motor?

Thanks in advance

Hi,
I agree with the guy that suggested valve seals.
Here's why:
You notice the problem occurs mostly at idle/low rpm and seems to clear while working the engine hard.
The engine creates steady, high vacuum at low speed and less compression. This sets up a situation where oil is most likely to be pulled past the valve stem. Although, it will get temporarily worse during deacceleration. Oil smoke from the exhaust during decel is a classic indication of bad valve stem to guide oil control while smoke during accel indicates poor piston ring sealing.
As the man said, a set of valve stem seals might help with this condition considerably. However, if the valve guides are severely worn, not so much.
Good luck.

 

[FordnMassey]

Hi,
I agree with the guy that suggested valve seals.
Here's why:
You notice the problem occurs mostly at idle/low rpm and seems to clear while working the engine hard.
The engine creates steady, high vacuum at low speed and less compression. This sets up a situation where oil is most likely to be pulled past the valve stem. Although, it will get temporarily worse during deacceleration. Oil smoke from the exhaust during decel is a classic indication of bad valve stem to guide oil control while smoke during accel indicates poor piston ring sealing.
As the man said, a set of valve stem seals might help with this condition considerably. However, if the valve guides are severely worn, not so much.
Good luck.

Hi,
Yes, that info about valve stem wear would make a good fit to the issue, but the smoke is lacking. I have a keen sense of smell for burning motor oil and there's nothing there. It's also never blowing smoke.
High vacuum situations could indicate a vacuum leak, as soeone previously suggested relating to the intake gasket.
Thanks

 

[skipmarcy]

Since the intake valve/seal is the one that will cause the oil burning for the most part, the most fouling will usually be on 1/2 the spark plug - the side towards the intake valve when screwed into the cylinder. IF your plugs have this type of fouling it is a sure symptom of valve seal/guide problem. For an oil burner you want a colder plug, not a hotter one. For fuel problems, a hotter plug. For either - fix the base problem.