MF 135 Runs beautifully for 30 to 45 minutes

[Waggawill]

Hi all,

I have a MF 135 with a standard motor co 4 cylinder petrol engine, it has given good service and is well looked after.

My problem is that it has developed a starts and runs perfectly for 30 to 45 mins then like someone turned on a switch it starts to misfire and splutters and if left will stop

What I have done thus fare to rectify.

• Carby kit (cleaned and checked)
• New distributer Plugs & Leads (Including Coil)
• Had a rattle up the front so new timing chain, governor cup and weights (this removed the rattle and the governor response improved)
• I have changed all the oil, engine, gearbox / transmission
• Reset tappets 010 & 012 so many times.
• Flushed the tank, cleaned the bowl filter and replaced the cork gasket.
• Using 95 Octane ULP with a little valve save added.
• Compression test 145psi all 4 cylinders.
• Oil pressure 60psi
• General running temperature anywhere from 10deg C up to 38deg C (Welcome to Australia), inland location mostly dry with low humidity.
• Ignition timing set at 10deg TDC via flywheel hole, I have not retarded at all.

It has me stumped, all the local mechanics require a laptop to conduct their trade, no real help there.
Any help or advice will be welcome. Thanks in advance,

Bill..

 

[California]

One potential cause for a fail after 30 minutes can be a blocked fuel tank vent, preventing more fuel to be sucked down to the engine.

Try removing the fuel cap when it does this. If vacuum makes the cap hard to remove, you've found the problem.

And welcome aboard!

 

[jaxs]

I'm not a fan of replacing parts before tests prove old one is bad but I make exception for condensers. If the tractor had a tune up including condenser recently I'd give odds the new condenser was bad from factory (many are these days). To confirm or eliminate fuel as cause try a couple things. Have a container to catch gas and wrench that fits carburetor drain handy when engine begins stuttering. Park tractor and let it sputter to a stop then pull drain. If stream isn't strong and/or slows you have a stoppage upstream. If that checks out remove air intake hose and run engine without it. Have starting fluid with straw handy and spray into carb when engine begins to stutter. If rpms pick up and can be maintained with start fluid there's blockage in float valve or jet. Swap in a known to be good coil. If ballast is in line temporarily bypass with jumper when engine falters. "Hot wire" from battery to coil to see if there's a break in wire leading to coil.

 

[zzvyb6]

see if it depends on the throttle setting (fuel rate is a problem) or if it temperature dependent (lux capacitor creating spark gets hot, clearence changes so no spark signal is generated. This is a gap issue on the flywheel on some motors.

 

[seville009]

When it sputters and dies, are you able to start it again right away?

I didn’t see in your list of things that you have done that you replaced the fuel filter. If you have not already put a new fuel filter in, you should do that.

 

[Birdhunter1]

When it sputters and dies have you tried pulling out the choke to see if it runs differently? When it starts sputtering and running rough take a can of something aerosol that is flammable (carb cleaner works well) and spray around the intake manifold. If there is a crack in the manifold it willsuck the liquid in for a second and run fine. I am going to guess you either have an intake manifold gasket that is sucking air as the manifold will start to pull away when it warms up, or you have a crack in the manifold which usually takes about 30-45 minutes to warm up enough to find.

 

[John0829]

Typical behavior of a failing ignition coil, check you spark when it happens. Is it blue or yellow? Many good fuel systems have taken the blame and been screwed up because of bad ignition.

 

[R134a]

Typical behavior of a failing ignition coil, check you spark when it happens. Is it blue or yellow? Many good fuel systems have taken the blame and been screwed up because of bad ignition.

Note ......what he said. Ignition coils don't last forever and they do strange things when failing.

 

[Waggawill]

One potential cause for a fail after 30 minutes can be a blocked fuel tank vent, preventing more fuel to be sucked down to the engine.

Try removing the fuel cap when it does this. If vacuum makes the cap hard to remove, you've found the problem.

And welcome aboard!

Thanks for the reply California, yep one of the first things I did fuel vent is operational. I even did a fuel temperature check before and after 30min no issue found.

 

[Waggawill]

I'm not a fan of replacing parts before tests prove old one is bad but I make exception for condensers. If the tractor had a tune up including condenser recently I'd give odds the new condenser was bad from factory (many are these days). To confirm or eliminate fuel as cause try a couple things. Have a container to catch gas and wrench that fits carburetor drain handy when engine begins stuttering. Park tractor and let it sputter to a stop then pull drain. If stream isn't strong and/or slows you have a stoppage upstream. If that checks out remove air intake hose and run engine without it. Have starting fluid with straw handy and spray into carb when engine begins to stutter. If rpms pick up and can be maintained with start fluid there's blockage in float valve or jet. Swap in a known to be good coil. If ballast is in line temporarily bypass with jumper when engine falters. "Hot wire" from battery to coil to see if there's a break in wire leading to coil.

Cheers jaxs: can and will try this, good hints thank you.

 

[Waggawill]

see if it depends on the throttle setting (fuel rate is a problem) or if it temperature dependent (lux capacitor creating spark gets hot, clearence changes so no spark signal is generated. This is a gap issue on the flywheel on some motors.

Thank you, I will look closer change out the cap and maybe the new coil as well. Cheers

 

[Waggawill]

When it sputters and dies have you tried pulling out the choke to see if it runs differently? When it starts sputtering and running rough take a can of something aerosol that is flammable (carb cleaner works well) and spray around the intake manifold. If there is a crack in the manifold it willsuck the liquid in for a second and run fine. I am going to guess you either have an intake manifold gasket that is sucking air as the manifold will start to pull away when it warms up, or you have a crack in the manifold which usually takes about 30-45 minutes to warm up enough to find.

Thanks birdhunter: I will try and see what I find, will report back.

 

[Waggawill]

Typical behavior of a failing ignition coil, check you spark when it happens. Is it blue or yellow? Many good fuel systems have taken the blame and been screwed up because of bad ignition.

Cheers John, one of my first thoughts, I guess I have thought I may have purchased a crook coil and cap, a cheap fix, so worth replacing.

 

[Waggawill]

When it sputters and dies, are you able to start it again right away?

I didn’t see in your list of things that you have done that you replaced the fuel filter. If you have not already put a new fuel filter in, you should do that.

Thanks Sev: Yes it will start but It will splutter straight away, it needs to cool down to obtain a normal run, so it is almost certain that this a heat related issue. with regard the fuel filter, there is a gauze filter above the glass bowl which I have cleaned, I see no debris in the bottom of the bowl. I flushed the tank more than once so it appears to be clean.

 

[Waggawill]

Fantastic reply's thanks to all, cheers from Waggawill.

 

[can do]

Hey

Hi all,

I have a MF 135 with a standard motor co 4 cylinder petrol engine, it has given good service and is well looked after.

My problem is that it has developed a starts and runs perfectly for 30 to 45 mins then like someone turned on a switch it starts to misfire and splutters and if left will stop

What I have done thus fare to rectify.

• Carby kit (cleaned and checked)
• New distributer Plugs & Leads (Including Coil)
• Had a rattle up the front so new timing chain, governor cup and weights (this removed the rattle and the governor response improved)
• I have changed all the oil, engine, gearbox / transmission
• Reset tappets 010 & 012 so many times.
• Flushed the tank, cleaned the bowl filter and replaced the cork gasket.
• Using 95 Octane ULP with a little valve save added.
• Compression test 145psi all 4 cylinders.
• Oil pressure 60psi
• General running temperature anywhere from 10deg C up to 38deg C (Welcome to Australia), inland location mostly dry with low humidity.
• Ignition timing set at 10deg TDC via flywheel hole, I have not retarded at all.

It has me stumped, all the local mechanics require a laptop to conduct their trade, no real help there.
Any help or advice will be welcome. Thanks in advance,

Bill..

Hi all,

I have a MF 135 with a standard motor co 4 cylinder petrol engine, it has given good service and is well looked after.

My problem is that it has developed a starts and runs perfectly for 30 to 45 mins then like someone turned on a switch it starts to misfire and splutters and if left will stop

What I have done thus fare to rectify.

• Carby kit (cleaned and checked)
• New distributer Plugs & Leads (Including Coil)
• Had a rattle up the front so new timing chain, governor cup and weights (this removed the rattle and the governor response improved)
• I have changed all the oil, engine, gearbox / transmission
• Reset tappets 010 & 012 so many times.
• Flushed the tank, cleaned the bowl filter and replaced the cork gasket.
• Using 95 Octane ULP with a little valve save added.
• Compression test 145psi all 4 cylinders.
• Oil pressure 60psi
• General running temperature anywhere from 10deg C up to 38deg C (Welcome to Australia), inland location mostly dry with low humidity.
• Ignition timing set at 10deg TDC via flywheel hole, I have not retarded at all.

It has me stumped, all the local mechanics require a laptop to conduct their trade, no real help there.
Any help or advice will be welcome. Thanks in advance,

B

Hi all,

I have a MF 135 with a standard motor co 4 cylinder petrol engine, it has given good service and is well looked after.

My problem is that it has developed a starts and runs perfectly for 30 to 45 mins then like someone turned on a switch it starts to misfire and splutters and if left will stop

What I have done thus fare to rectify.

• Carby kit (cleaned and checked)
• New distributer Plugs & Leads (Including Coil)
• Had a rattle up the front so new timing chain, governor cup and weights (this removed the rattle and the governor response improved)
• I have changed all the oil, engine, gearbox / transmission
• Reset tappets 010 & 012 so many times.
• Flushed the tank, cleaned the bowl filter and replaced the cork gasket.
• Using 95 Octane ULP with a little valve save added.
• Compression test 145psi all 4 cylinders.
• Oil pressure 60psi
• General running temperature anywhere from 10deg C up to 38deg C (Welcome to Australia), inland location mostly dry with low humidity.
• Ignition timing set at 10deg TDC via flywheel hole, I have not retarded at all.

It has me stumped, all the local mechanics require a laptop to conduct their trade, no real help there.
Any help or advice will be welcome. Thanks in advance,

Bill..

Hey good day, & welcome to TBN. I take it that it's a Continental engine? Is the original heat shield still on the engine between the fuel tank, & above the exhaust manifold? I'm just guessing, But it could be a vapor lock issue. The fuel entering the carb. is getting to hot seeing that the weather is quite warm down under. It does sound like a fuel flow problem. I recently had my M-F 50 gasoline in for some other service, But they said it was running a little rough, & did a simple carb. adjustment; So there is no sputtering or hesitation anymore since the adjustment. You should be able to run her on 87 octane. As far as timing I installed a electronic ignition a long time ago, & never had any issues with timing; Or tune-ups. It's a old thread I posted a couple years ago here on TBN . That was the best thing I did for my tractor. I'm sure it is something simple. Let us know what you find.

 

[CanyonRim]

Waggawill,
FYI , When a coil goes bad it will be hot to the touch when the motor runs bad a quits. You have lots of leads to track down from the TBN group. Good luck. Enjoy your day.