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766 stumbling


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Hello All, 

My 766 (D360) developed a stumble this year mowing hay. I changed the air filter and the fuel filters and it seemed like it was running alright although it would still have an occasional miss. Started it up this AM after a couple weeks of downtime and it was OK at idle. I ramped it up to 1/2-3/4 rpm and it was good for probably 15 to 20 seconds, but then started stumbling for 10 seconds and then ran rough. Brought it down to idle and it was rough for 10-20 seconds and then started to smooth out.

Based on the above I'm thinking it's fuel supply? What would you guys go after first? Want to be efficient in troubleshooting since I use this tractor for snowblowing...so the clocks ticking, so to say...




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Hand pump primer on Inj Pump.

Don't want them leaking fuel up and out when you extend it to hand pump.  Possible for it to suck air into fuel system when running if plunger seal and top seal are bad.

Easy fix if seals are bad.

Jus 1 if the easy things to check.

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4 hours ago, snoshoe said:

First suspect is valve on bottom of tank plugged.

Ding ding ding.

Should started at the beginning of the process. Thanks for the humbling reminder. 

Took the line off at the filter and it was running slow. puffed some air up through the tank valve and she us running good at the moment. Will need to either pump out/drain the tank or more likely I'll use it until it clogs or I'm near empty and the work to rinse out the tank. With a flashlight I don't see excessive sediment or debris, but obviously something was in there unless it was just gunk. 


Thanks again. Saved me some fooling around.



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Doesn’t take much to plug that valve/line.  Your shot of air probably vaporized the chunk of sediment that had built up, and maybe it broke into specs small enough to pass into the filters, and be filtered. If you don’t see crap in the tank, I’d bet it’ll be good for a long while and wouldn’t think more about it.  If you look close and Do see a little crap in there, let it set for a while sometime when your not needing it, and then you could try “vacuuming” the particles out with a syphon hose/suction gun/pump.    Does the drain valve function? Let it set…then drain a few quarts out. 

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The dirt daubers, birds and other pests will build nests ahead of the air cleaner.

Remove the air cleaner and make sure the tube running from the air cleaner to the grill above the radiator is clear.

You will be surprised what is found in here.

And it don't take much of a restriction to change performance.

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