Frustrating 1020

[Grandpa W]

I use a 1986 Massey Ferguson 1020 manual tractor for cutting grass along with a Buehler Farm King 60” 3pth finishing mower. This is a great little 21hp tractor with the Toyosha 3 cylinder diesel engine that was serviced last August by a knowledgeable and trusted tractor mechanic who is not available for me to contact at this time.

This year the tractor is losing power (bogs down) when cutting anything but the lightest most sparse grass. It starts fine, sounds good and even when bogging down there are no unusual or scary sounds, it just slows down.

To date I have taken the air box apart to make sure there are no blockages and installed a new air filter – no change. Drained old fuel from tank and flushed the tank. Replaced the fuel line that was probably original and deteriorating. Changed the fuel filter (full of old fuel line), cleaned the bowl, bled the line.

It starts and sounds better but the bogging issue remains. I searched the forums and found similar but different stories and am hoping for some direction where to look next. The mower can easily be turned by hand so I don’t suspect any restrictions with it.

Although mechanically inclined I have no experience working on tractors and the only thing I know about diesel systems is that it comes out of the yellow cans, so please be patient.

 

[JWR]

When did it begin to lose power -- suddenly or gradually over how long ? How many hours on it? Has it operated normally (without bogging down under full load) at any time since it was serviced last August? [You have already done the first things I would have done making sure there were no air obstructions, replacing fuel filters and cleaning out old fuel.

 

[Grandpa W]

I used the tractor half a dozen times since the service to cut grass last year and moved snow throughout the winter as well without issues. I bought the tractor 3 years ago with the meter broken at 729. Original owner claims the meter only quit working a month or two before, but I doubt that. It did sit for approx. 2 months unused after the last snow clean up until the first lawn cutting.

 

[JWR]

Those tractors have a great reputation for doing a lot of work for their size as well as for reliability. I have a friend who owns one. I suspect other folks will come on here soon and have some ideas about your problem.
So the latest clues you gave us seem to be

1. that the tractor was working fine well after the service last August
2. it worked OK during winter snow removal
3. it sat dormant for about 2 months after the snow removal
4. now it starts and runs well until it faces a load like cutting grass with a finish mower

The tractor seems to have too low hours and was working fine until the end of snow removal season so unlikely to have compression issues. Diesels run on nothing but compression, fuel and air. In your case it must be fuel or air.
A few wild assed guesses:

• a mud dobber or other pest built a nest or obstruction somewhere restricting intake air ?
• one of the two fuel pumps has a problem ?
  • the lift pump is not getting much gas up to the input of the injection (high pressure) pump -- you can pull the fuel line right at the input to the injection pump and crank the engine to see if you have robust flow or just a bare trickle -- you have at least a bare trickle or the engine would not run (!)
  • the injection pump could have some issue and be failing to provide adequate flow under load. Will it run flat out full rated rpm? If so it is unlikely to be the injection pump.

I guess I lean toward some sort of air flow obstruction. Let's see what others say. Good luck !

 

[seville009]

Is the mower possibly set for too low of a cut?

Test it by raising it noticeably (say maybe three inches), then mow for a bit and see if it still bogs down.

 

[Grandpa W]

Those tractors have a great reputation for doing a lot of work for their size as well as for reliability. I have a friend who owns one. I suspect other folks will come on here soon and have some ideas about your problem.
So the latest clues you gave us seem to be

1. that the tractor was working fine well after the service last August
2. it worked OK during winter snow removal
3. it sat dormant for about 2 months after the snow removal
4. now it starts and runs well until it faces a load like cutting grass with a finish mower

The tractor seems to have too low hours and was working fine until the end of snow removal season so unlikely to have compression issues. Diesels run on nothing but compression, fuel and air. In your case it must be fuel or air.
A few wild assed guesses:

• a mud dobber or other pest built a nest or obstruction somewhere restricting intake air ?
• one of the two fuel pumps has a problem ?
  • the lift pump is not getting much gas up to the input of the injection (high pressure) pump -- you can pull the fuel line right at the input to the injection pump and crank the engine to see if you have robust flow or just a bare trickle -- you have at least a bare trickle or the engine would not run (!)
  • the injection pump could have some issue and be failing to provide adequate flow under load. Will it run flat out full rated rpm? If so it is unlikely to be the injection pump.

I guess I lean toward some sort of air flow obstruction. Let's see what others say. Good luck !

Thank you for your help, its greatly appreciated.

 

[Grandpa W]

Is the mower possibly set for too low of a cut?

Test it by raising it noticeably (say maybe three inches), then mow for a bit and see if it still bogs down.

Thank you , yes I have tried that as well but it makes no difference.

 

[seville009]

One more question- when it starts to bog down, if you lift the 3 pt/mower with the mower still running, does the bogging stop?

If it still bogs with the 3 pt raised, shut off the pto/mower to see if the bogging stops.

That all would just help to identify if the mower itself is the cause.

Is the gear oil on the mower gear box full?

 

[Grandpa W]

I have been thinking more about the mower as well. The tractor seems to run great without the mower turned on, but I have not tried a different attachment yet.
The mower gear oil was confirmed when put away last fall, shows no leakage and is cool to the touch after operating. I have easily spun the blades by hand and also took off the top covers and spun the system easily by pulling on the belts.
I am planning to try a different attachment later today to either rule out, or confirm the mower or tractor.
I will post an update when completed.

 

[rScotty]

It sure does sound like it is starving for fuel. A good test is to take it out to the road and drive up a slight incline for awhile. If it starts out strong and then slows.... and then if you let it idle for awhile and it does it again.... then that generally means the fuel filter is not passing enough fuel. What is happening is when you use up the reserve in the filter it just loses power becuase it isn't getting fuel fast enough.

If so, go through that fuel feed system again. Start with the fuel cap vent and then all the way through the filter and to the input to the injection pump. You may have to replace some hoses and disassemble the fuel filter to look inside. If it is starving for fuel, the problem is in that fuel feed somewhere.

rScotty