Tractor loosing power and stalling

[Critter]

Our tractor has started loosing power and stalling while mowing. Could you folks give us a hand troubleshooting this?

Model: M8200, 1100 hrs, regular maintenance
Mower: mower conditioner
Recent maintenance: filter change

The tractor has not had problems until today, the first day mowing this year. The mower conditioner requires the tractor to be run almost full power.
While it worked well most of the day, after about 4 hours it periodically started loosing power. This progressed to loosing power, followed by the engine stalling. It could not be restarted for 5 - 10 minutes, then the tractor ran normally until it stalled again. How long it worked at a time was variable.

Observations: while losing power, the fuel bowl stopped being full, with diesel froth slowly filling from the top.

Is this a problem with the engine-driven fuel pump? If so, why is the stalling periodic, and why does it recover after 5 - 10 minutes?

 

[motorhead]

Welcome to OTT.
First I would check the fuel filter to see if it is clogged. I would check the fuel gravity flow from the tank to the inlet of the fuel pump. If it is slow then the passage in the tank is clogged.It can be cleared by removing the fuel cap and carefully using compressed air to blow backwards toward the fuel tank. DO NOT DO THIS WITHOUT FIRST REMOVING THE FUEL CAP. If both the above issues are not present, filter clean and fuel flow ok then i might suspect the primary fuel pump is weak or failing. A usual exterior sign of a bad fuel pump will be fuel leakage present around the pump. This isn't always the case.

 

[Critter]

Thank you for your suggestions, motorhead.

Unfortunately, we're still looking for the problem.

• The filter has been replaced
• The o-ring on the fuel bowl checked (ok) and reseated
• The fuel line between pump and tank was blown out in both directions and was not blocked.
• The semi-local tractor mechanic thought it couldn't be the the fuel pump because the foam in the bowl indicates its still supplying fuel. He thought it might be sucking air into the fuel line somewhere.

The tractor seems more prone to stalling when it is following along a slope and tipped towards the right.

Any ideas?

 

[birddogger]

because the foam in the bowl indicates its still supplying fuel.

I'm gonna hafta say, no. The filter bowl should be remaining full, foam indicates restricted in-flow. Siphon the fuel out of the tank into a clean fuel can to catch it. Disconnect the tank-to-filter fuel line and run a brush through it, a .25 caliber rifle brush will do in a pinch; or a cotton ball on the end of a wire coat hanger fashioned into a long swab. Check where the line meets the filter, that debris hasn't plugged the inlet area.

 

[motorhead]

I have worked on many VW and Mercedes diesels that the intake flexible fuel line between the tank and fuel pump became porous and would suck air. I don't know what the M series has but it could be worth replacing if it hasn't already been replaced.
I guess to completely narrow down things you could rig up a separate small fuel tank and return line to it and see if you still foam at the fuel strainer. Have you checked your oil level to see if it has diesel fuel dilution from a leaking fuel pump diaphragm?

 

[Critter]

Thanks guys, I'll check on these points. At this point, if its the fuel pump we won't be able to get a new one until after the bailing, and I don't know what spare parts we have in stock. So we'll either limp along, and hopefully fix this soon ...

 

[Critter]

Update: it turns out the tank-to-filter fuel line had hay in it. Not enough to be noticeable when blowing out the line with compressed air, but enough to block flow. The hay must have got into the tank last year when the fuel cap fell off, and it wasn't noticed immediately. Now we're going to have to figure out how to clean it out of the tank.

Thanks for the help, everyone

 

[motorhead]

Thanks for telling us you found the problem and what it was.
A lot of forums a guy asks a question about a problem and when he fixes it we never hear what it was.