MF20 starts but won't stay running

hershwork

Member
I have an MF20 that began to have trouble running. I would have to mash on the gas to (what should have been) too high a running RPM. It ran labored--this was over the course of cutting a football field with a flail mower to try to level it a little--for around 4 hours. I was running the mower really low down so it would take down grown over weeds--hard work. Only in first gear. A fair amount of black smoke and I had to go over several places multiple times because it was making the slip clutch burn. But I digress...

A couple times it would just peter out and quit running. Each time that happened, it was a really gradual process, almost like it was running out of gas, and I would pump the foot gas pedal with almost no effect. There was at least 1/2 a tank of gas at this point, cutting on a flat surface, so no sloshing.

Then, it would start again almost immediately and run a lot better, but still weaker than normal. It became weaker running and then I was just worried I wouldn't be able to get it parked in time. Each time I started it though, it started right up, only to run for 20 seconds and diesel to a stop.

I read several threads related to these symptoms and decided that I needed to replace the fuel transfer pump. I got one from this website and just replaced it this last weekend. The old one had a bunch of gunk in it and not sure how it pumped anything very well--lots of dirt/sludge/rust on the pump diaphragm. So I replaced it, bled the fuel system, and it does about the same thing....Starts, runs briefly, shuts off.

The only other thing I can find that seems related, is that the fuel pedal has a pin that's come out, so that it swivels freely without changing the throttle position. This is a tension pin i think. The hand adjustment seems to still move the throttle, though, so don't think the foot pedal pin would affect it.

Injection pump seems to be developing good pressure because it sprays fuel through the bleeder screws. Any thoughts would be greatly appreciated.
 

When were the fuel and air filters last changed? Has it been setting for extended periods of time?

If the hand throttle moves the linkage and adjusts the rpms, I doubt very much a pin missing from the foot throttle is affecting the engine, only your ability to use the foot throttle.

Best to leave the word "gas" out of descriptions related to your diesel. Use diesel or fuel instead. And tell what the engine is to begin with, to get the best response for engine related help.
 
Going through a repeat issue with a 245, 3 cylinder diesel, started it last week and it died as I throttled it up and wouldn't start again. Two years ago it quit in a barn and I had to tow it back to where the tools were. The fuel filter looked like a buzzard had thrown up in it, replaced lift pump, no go, pulled the fuel shut off valve off the tank and it was severely clogged with bits of small rust particles, cleaned it out and ran fine for two years. I removed the fuel line that comes from the tank to the lift pump and it had a blockage of the same junk as before so now the valve will have to come off and be cleaned. The tractor sits outside and over the years the inside of the tank has begun to rust so eventually it will be replaced or cleaned and coated but I thought it would last longer than this, always had clean diesel. I'm going to flush it out better this time and drop a couple of magnets in it and see if it works a bit longer. Your comment about debris from the lift pump is what makes me think your fuel shut off valve needs to be removed and cleaned at least as a starting point. Good Luck with it!
 
Black smoke usually means the fuel/air mixture is off as in the engine isn't getting enough air for the amount of fuel. Start by replacing the air filter and checking all air passages for blockage like mouse or squirrel nests.

Running out of power/dying is a fuel related problem, just the opposite of the black smoke. The fuel delivery system has filters. The first is at the fuel tank. It probably has a screen fitted up into the tank. Replace that since you have evidence that it has failed with the gunk you found in the transfer pump. If it has a sediment bowl, remove that and the screen that is fitted above that. Make sure that screen is intact and clean. Next replace the fuel filter after allowing fuel to flow from the transfer pump to its inlet by removing the fuel line at the intake side and catching the fuel in a bucket by using a funnel with a fine screen to catch any gunk that was in the line between the fuel tank and the filter housing. Now replace the fuel filter or filters if it has 2. Bleed the filter housing first to make sure you don't have air in the line coming to it, then the outlet from the filter and finally bleed air out of the line coming to the injector pump. Finally, bleed each injector. The diesel system does not work with air in it.
 
(quoted from post at 12:04:29 11/28/22) Black smoke usually means the fuel/air mixture is off as in the engine isn't getting enough air for the amount of fuel. Start by replacing the air filter and checking all air passages for blockage like mouse or squirrel nests.

Running out of power/dying is a fuel related problem, just the opposite of the black smoke. The fuel delivery system has filters. The first is at the fuel tank. It probably has a screen fitted up into the tank. Replace that since you have evidence that it has failed with the gunk you found in the transfer pump. If it has a sediment bowl, remove that and the screen that is fitted above that. Make sure that screen is intact and clean. Next replace the fuel filter after allowing fuel to flow from the transfer pump to its inlet by removing the fuel line at the intake side and catching the fuel in a bucket by using a funnel with a fine screen to catch any gunk that was in the line between the fuel tank and the filter housing. Now replace the fuel filter or filters if it has 2. Bleed the filter housing first to make sure you don't have air in the line coming to it, then the outlet from the filter and finally bleed air out of the line coming to the injector pump. Finally, bleed each injector. The diesel system does not work with air in it.

The shutoff valve for the tank was a problem before--or I thought it was, anyway--and I cleaned it and the fuel tank at that time, maybe a couple of years ago. The fuel still runs clear from the tank to the transfer pump.

After the transfer pump, I believe it goes to the filter with the glass jar. I bled that at the top of the filter, where the fuel line comes in at the top, and it seems to get there fine.

From there, it goes to the injection pump, and I bled it at the two bleeder screws on the pump.

I don't follow where along that route you're saying the problem is...
 

When did you last change, not just bleed, the fuel filter(s)? When did you last change the air filter? Check the entire air intake system to be sure something isn't causing a blockage in it. Has the tractor set for extended periods of time? Try leaving the fuel cap loose and see if it stays running, if it does, that would indicate the cap isn't venting.
 
(quoted from post at 00:56:05 12/04/22)
When did you last change, not just bleed, the fuel filter(s)? When did you last change the air filter? Check the entire air intake system to be sure something isn't causing a blockage in it. Has the tractor set for extended periods of time? Try leaving the fuel cap loose and see if it stays running, if it does, that would indicate the cap isn't venting.

The entirety of the time I've owned the tractor--around 10 years--I've used it for 10-20 hours per month, on average. Some significantly more than that. Sometimes it has been unused for a couple of months.

I've cleaned out the air filter housing and the air filter here and there. Don't believe I've ever replaced it.

More or less the same with the fuel filter. The only one I know of is the one with the glass bowl on the left side of the engine. I've taken it apart, cleaned it out, washed it with clean diesel and put it back together. I've checked and bled water out of the trap.

To me it seems very much like a fuel starvation problem. If the fuel is clear to the transfer pump, that seems to eliminate the fuel tank, fuel tank filter, and line between the tank and transfer pump as problems. The transfer pump was replaced. Bleeding the line at the fuel filter, and having fuel come out, seems to indicate the line to that point is OK.

I can try leaving the cap off the tank. Is there something else to do with the fuel filter other than empty it and clean out the inside?
 

The filter element is the metal cylinder above the glass bowl. You periodically replace the filter element to get rid of what is trapped inside it, even if you drained it and cleaned the bowl. If you have had water in the bowl and dirt chances are very good there is crud inside the filter, even if the flow seems good. 853944M92 is the MF part number for a three pack.

You replace a dry air filter periodically to get rid of the material trapped in it, even if you have blown it out over the years.
 
(quoted from post at 02:21:33 12/04/22)
The filter element is the metal cylinder above the glass bowl. You periodically replace the filter element to get rid of what is trapped inside it, even if you drained it and cleaned the bowl. If you have had water in the bowl and dirt chances are very good there is crud inside the filter, even if the flow seems good. 853944M92 is the MF part number for a three pack.

You replace a dry air filter periodically to get rid of the material trapped in it, even if you have blown it out over the years.

Makes sense. I'll replace those and let y'all know what happens.
 

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