Mowing Engine Misfires while mowing

[pathunt]

Would appreciate help from anyone who has suggestions for a Massey Ferguson 250 series (251) that misfires under load.

The motor starts well when cold. It warms up ok, but starts to misfire when throttle is applied. It misfires at 540 PTO and the rpm surges while in use.

The fuel looks clear in the filter.

The fuel is new, off-road diesel.

It just died coming up the road to the house.

What should I be looking at first?

I will post the results of trying any suggestions. Thanks.:confused2:

 

[Soundguy]

Misses or looses rpm?

 

[pathunt]

Misses or looses rpm?

Soundguy -

Engine misses at 540 pto. Sounds like it is struggling. It will take more throttle, but does not sound "right".

When set at mowing speed the rpm surges.

Thanks.

Starkiller Hollow

 

[George2615]

Two things come to my mind.
1) Water in the fuel.
2) Fuel filter needs to be changed.
A third thing could be the fuel pump but its rare that they fail.

I just had a similar problem with my gas powered generator / welder. I had just added 3 gallons of fresh gas (bought the day before) to the tank and fired it up for a welding job. Under load it started missing. I shut it down and stuck the tank with a dipstick coated with a paste that detects water. The paste is yellow but turns red if water is detected. It turned red so I siphoned out what I could, went and bought fresh gas at another station, tested that gas before putting it in, added a bottle of dry gas and fired it up again. After a few minutes it ran fine again. Now I test my gas and diesel for water before I fill the tank. I buy the tube of water detection paste at my local fuel supplier.

 

[Soundguy]

that sounds more like a bog down than a miss.

i'd suspect fuel delivery when a diesel won't make rpms or keep them, and not overloaded.

 

[murphy1244]

Two things come to my mind.
1) Water in the fuel.
2) Fuel filter needs to be changed.
A third thing could be the fuel pump but its rare that they fail.

I just had a similar problem with my gas powered generator / welder. I had just added 3 gallons of fresh gas (bought the day before) to the tank and fired it up for a welding job. Under load it started missing. I shut it down and stuck the tank with a dipstick coated with a paste that detects water. The paste is yellow but turns red if water is detected. It turned red so I siphoned out what I could, went and bought fresh gas at another station, tested that gas before putting it in, added a bottle of dry gas and fired it up again. After a few minutes it ran fine again. Now I test my gas and diesel for water before I fill the tank. I buy the tube of water detection paste at my local fuel supplier.

Try using a Mr.Funnel, water can not go thru it.

 

[pathunt]

Soundguy, George, and Murph:

Thanks for suggestions. Will try draining fuel, and changing the fuel filter. The Mr. Funnel sounds like something that should be in the shop anyway.

Next week....

Starkiller Hollow

 

[pathunt]

Hate to ask - but pictures in the Agco manual are so dark they are almost illegible. Having hard time locating fuel shutoff for tank and fuel lift to refill the bowl. Trying to locate all the key points before I try to fix it. Can get the fuel pump cartridge locally on Monday.

Have found a few videos, but none cover the 251 XE.

Signed,

Ignorance is not bliss.:laughing:

 

[pathunt]

All:

Called the Massey dealer. About 50 miles away. He was very helpful.

Found fuel lift pump, lever, and shutoff valve. Will get the filter from the dealer this week and replace it.

For newbies like me who may be reading the thread - Procedure runs something like this:

Take fuel filter
loosen nut at top
take filter and bowl off
clean bowl
replace O-ring on little nub inside the top of the housing
replace gasket in top of filter housing
replace gasket in bowl
screw the bolt almost tight
pump fuel until fuel comes out between the gaskets
tighten bolt snug
pump fuel until lever starts to feel pressure behind it
start tractor
if no start, pump lever four or five times and try starting again
should start, run rough for a little bit, and then smooth out.

Thanks to all -

Starkiller

 

[pathunt]

OKdokay -

Changed the fuel filter. Filled up the fuel bowl. Could not get it to start. Recharging battery. No joy. Will keep you posted. Appreciate any suggestions. Thanks.

 

[MAN IN BLACK]

OKdokay -

Changed the fuel filter. Filled up the fuel bowl. Could not get it to start. Recharging battery. No joy. Will keep you posted. Appreciate any suggestions. Thanks.

Maybe air in the lines...try purging it some more?

 

[pathunt]

Thank You.

Will take the fuel bowl and filter off again, check seals, purge, then will charge bowl and try again. Is it necessary to bleed/purge the lines going to the injector pump?

Starkiller

 

[Soundguy]

If needed

 

[doxford jim]

It is essential that the fuel lines to the injectors get bled properly of air. Air readily compresses so when the injection pump puts out diesel fuel under pressure, any air just compresses and nothing happens. The air compresses and does not open the fuel injector. Liquids under pressure will open the fuel injector - be it water, oil or diesel. Liquids cannot be compressed but gases can.
Bottom line is all air must be vented from the fuel line (loosen compression nut on injector to allow air to escape) or the injector will not be allowed to do it's job properly.

 

[445A]

Father in law had a problem that was similar. More throttle would make it buck and snort at a higher RPM. He found a small crack in the top O ring on the fuel filter. Just big enough to suck a small amount of air, but it still started cold and ran, poorly that is. At this point on your tractor, I would crack all steel supply lines at the injectors/nozzles turn over engine and check for fuel. If the fuel has bubbles in it keep this up until it runs clear, no bubbles. If the bubbles persist, after a minute or more you are sucking air in from somewhere. If fuel clears up tighten fittings at I/N and start. Be advised: I am not a diesel mechanic, that's why I'm a TBN member!:thumbsup: Oh another thought, make sure you remove all old gaskets when replacing with new. 2 stacked o rings are not better than 1, and will suck air. Please don't ask how I know this!:ashamed: Let us know what you find, so we all benefit from this. Thanks and happy diagnosing. 445A

 

[pathunt]

If needed

To new replies as well - Going over the tractor, found that the fuel valve from the tank was not bolted tightly to the firewall and had been wiggling around. It's a little cold here today so will wait until it warms up.

When I bleed the line at the injector pump, and at the injectors - can I just loosen the nut and press the paddle on the fuel pump to force fuel through the line?

Thanks

 

[JWR]

OKdokay -

Changed the fuel filter. Filled up the fuel bowl. Could not get it to start. Recharging battery. No joy. Will keep you posted. Appreciate any suggestions. Thanks.

Yeah, that's because air got in the lines while you were putting in the filter. Has happened to me more than once. Hard to avoid. Once you are sure that all the connections & gaskets are snug, go look for the priming pump. I could not tell if you were already using that. If it cranks well and still will not start, you are going to have to bleed the injector lines. Loosen the fuel line nut at the top of the injectors, one at a time and crank briefly until fuel squirts. Tighten that one back and go to the next one. It should then start and run. One hopes that is the end of the story. Let us know !

 

[pathunt]

My thanks to all of you - Soundguy. MIB. George, murphy1244, doxford jim, 455A, and JWR....

Re-charged battery
Went back to fuel pump - used paddle.
Fuel still leaking and did not start.
Cracked nut on Delphi Fuel injector pump, used paddle, and retightened.
Turned engine over and it started :dance1:

Life is good!

Starkiller Hollow.

 

[JWR]

Great news. Sounds like your air leak was at/near the injection pump. That paddle (priming pump) only affects fuel on the low pressure side of the pump. Since that worked, no need to bleed all the injectors (this time.) You lucked out. On an older Kubota I had to bleed the injectors on the high pressure side of things. On a John Deere 4700 I had to use the primer paddle as you did. On my newer Massey Ferguson (and probably a lot of newer tractors) an electric fuel pump is involved which keeps pumping (and recirculating) fuel as soon as you turn the switch and before you crank. Those are said to be "self-priming" but that means on the low pressure side. Good luck to ya !

 

[pathunt]

Final Answer -

1. Cleaned out fuel tank petcock valve. It was clogged. Drove down to gravel pit, loaded FEL and automatic furthest distance-from-house shutoff mechanism kicked in. :=(
2. Got it started later that night and drove back to shop.
3. Cleaned petcock valve again next day, drained tank, installed inline filter between tank and petcock valve. Checked at lift pump - fuel flow restored.

Starkiller