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

[FordnMassey]

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 brand/type of plug are people using in this motor?

Thanks in advance

 

[ROUSTABOUT]

Umbrella cup stem seals for the valve stems. Can be done without removing head

 

[zzvyb6]

Your motor is not running hot enough to clear the carbon fouling when it starts misfiring. Loading it heats the head and the fouling is ablated off.

Thermostat ? if not, get one. If so, get a hotter one.
block a portion of the radiator.
set the idle rpm up to help with some warmth.
get a spark plug 2 ranges above your current designation.
put on a thermo-energizing fan. Shuts off when the motor temp drops.

stop the motor when its misfiring and pull the plugs to see if its just 1 cylinder behaving badly.

Tell us what you find !

 

[FordnMassey]

Umbrella cup stem seals for the valve stems. Can be done without removing head

Hi Roustabout,

What are umbrella cup valve stem seals and why would they help?
Thanks

 

[FordnMassey]

Your motor is not running hot enough to clear the carbon fouling when it starts misfiring. Loading it heats the head and the fouling is ablated off.

Thermostat ? if not, get one. If so, get a hotter one.
block a portion of the radiator.
set the idle rpm up to help with some warmth.
get a spark plug 2 ranges above your current designation.
put on a thermo-energizing fan. Shuts off when the motor temp drops.

stop the motor when its misfiring and pull the plugs to see if its just 1 cylinder behaving badly.

Tell us what you find !

Hi,

Thermostat is 80deg C, or 172F. I installed it 12m ago an it definitely works. 5 minutes of driving, not working hard, has it at 60C, if we can trust the gauge.

I'll get hotter plugs and see what happens.

I'll get back with the outcome.

 

[mikester]

Try buying premium gas and from a different vendor. I find costco gas runs like a BOS on my bikes, even their "premium".

 

[Quebecguy]

I have a misfiring and spark plug fouling issue

The fouled spark plugs might be a symptom of the misfire and not the cause. Misfires on my old gasoline International are usually the result of a type of corrosion where the plug wires meet the distributor. When was the last time you replaced the distributor cap? I have found that a liberal application of di-electric grease in these areas prevents misfiring (or at least postpones it!).

 

[FordnMassey]

Try buying premium gas and from a different vendor. I find costco gas runs like a BOS on my bikes, even their "premium".

Hi,
I've experienced this too, and did try premium (98 v 91 octane) fuel, one tank from empty, and got no change.

Interesting story there, I was driving a Kombi around Europe in '99. When I filled up in Spain, the motor ran beautifully. Smoother and more pull across the whole rpm range, but especially low rpm. Turns out Spain was still selling leaded fuel, where the rest of Europe had gone to lead replacement. Motors made for leaded fuel are never the same without it, in my opinion.

 

[FordnMassey]

The fouled spark plugs might be a symptom of the misfire and not the cause. Misfires on my old gasoline International are usually the result of a type of corrosion where the plug wires meet the distributor. When was the last time you replaced the distributor cap? I have found that a liberal application of di-electric grease in these areas prevents misfiring (or at least postpones it!).

Hi,
Good point on the cause or effect of the misfire.
Dizzy cap and rotor and points new 12m or 50 running hours ago. I do get the corrosion on the lead ends and cap contacts, so I'll do the dielectric grease idea.
Leads were also new, but turns out they're of low quality and arc out of the rubber end covers if they get close to anything. I have the ends wrapped in electrical tape which works, while I wait on new ones. I've heard that the ones with hard plastic ends are the better type. Anyone got some input on this point?

 

[Jerry/MT]

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 brand/type of plug are people using in this motor?

Thanks in advance

A hotter plug will help this problem. Also make sure that your mixture setting is not too rich, your ignition timing is correct, and the point dwell is per spec. Does your engine hit the correct coolant temperature during your duty cycle? If it doesn't warm up, that could contribute to the problem.