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755 Fuel problem

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Mike Flitcraft
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2001-05-14          28147

I'm having a problem with my 755 and was hoping someone on here can be of help. The problem has to do with fuel delivery. When under load (mowing, snow removal, etc), the tractor will suddenly lose all power and barely run. After shutting it down, bleeding it per the shop manual, it works fine for a few hours, then the same thing happens. I've checked the fuel pump delivery volume, and it's per specs. I should add that when this happens, the fuel filter bowl is almost empty. I'm thinking it's an air leak, but the way it acts, I don't know where to look or what to suspect. If anyone has any ideas, I'd be more than willing to listen. Thanks in advance for any help!

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755 Fuel problem

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Norm
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2001-05-14          28148

I'm no expert, but the fact that the fuel bowl is empty suggests to me that the fuel pump may be the culprit. You say you've checked the delivery capacity, but the problem is obviously intermittent. If not the pump itself, perhaps wiring to it. Could an air leak on the suction side of the pump be a possible cause? I'll raise that to the board for someone else to comment. ....

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755 Fuel problem

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Mike Flitcraft
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2001-05-14          28154

Thanks for the response. I suspected the solenoid for the fuel cut-off as it's impossible to know when it's going to happen and I can't 'watch' it the whole time I'm using the tractor. I did check the connector to the solenoid and it was corroded. After cleaning it, the problem continues.
I'll might add that since this has started happening, the tractor doesn't seem to have the power it did. Before this, when I had the mower running, the rpm's would barely waver when cutting tall grass. Now, it seems to drop a few hundred rpm when under load. There's also a faint odor when working the tractor, which I can't really describe, only that it's got to be coming from the exhaust.?. I've not noticed any smoke. ....

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755 Fuel problem

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Paul Fox
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2001-05-14          28169

Not familiar with the 755 in particular, but my 750 is gravity feed from the tank to the fuel bowl via a pleated filter. If the bowl is not staying full, either you got crud in the tank/line or the filter is plugged. ....

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755 Fuel problem

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2001-05-15          28187

I wonder if it's possible that the problem is more predictable than thought. For example, it might happen after a long period of heavy use such as rotary cutting, but never happen while lugging around doing loader work. If so, that suggests the gravity flow from the tank is insufficient. Crude in the lines, a partially clogged or open shut off valve etc. might do it. I've heard that some tractors have rough filters inside the tank. The solenoid is a possibility or the switch, and trouble shooting intermittent electrical problems is a pain. To trouble shoot it, you'd have to know if the solenoid is normally off or on. Then, create the condition and then see if voltage to the solenoid is present or not. A technician might apply external voltage to the solenoid to verify that it does work, but amateurs shouldn't attempt such procedures. Except for the empty fuel bowl, the governor could cause the problem described, and that might be kept in mind. ....

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755 Fuel problem

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DanaT
Join Date: Jun 1999
Posts: 138 Clay Center,Ks
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2001-05-15          28191

I was told that there is another filter inside the tank of a 1996-855. It might be worth checking a shop manual. ....

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755 Fuel problem

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Mike Flitcraft
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2001-05-15          28192

Thanks for all the input guys. I guess the logical thing to do first is pull the tank and blow out all the lines. I checked the shop manual and there is no mention of an internal filter in the tank, but who knows? When and if I ever figure this out, I'll post the solution for future reference. Thanks again. ....

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755 Fuel problem

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Doug L
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2001-05-15          28204

Mike,
Had the same exact problem with my 1987 855 last year. There is a fine screen filter at the end of the fuel line inside the tank which was completely clogged. The fix was to remove the tank, then the pipe/gage assembly, clean the filter and flush the tank. The amount of debris and sludge in the tank was incredible. Be sure to use a brush or rag on the end of a stick to loosen up the stuff on the inside of the tank. I've only had the machine for a few years, so I can only assume that the previous owners were not to careful about cleaning the debris away from the filler neck when refueling. ....

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755 Fuel problem

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Mike Flitcraft
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2001-05-15          28213

Doug,
Thanks a million for the info! I was hoping someone who experienced the same symptoms would be out there somewhere. My tractor is a '91, so it's likely it has the same screen setup. Looks like my evening is planned :)
Mike ....

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755 Fuel problem

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Mike Flitcraft
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2001-05-16          28245

Here's one for the books! Well, I believe I've found the problem. I pulled the tank and here's what I found. The fine mesh screen is attached to the pickup tube with a piece of hose. That hose had split and I found the screen at the bottom of the tank. I also found, believe it or not, a plastic cap (one of those that are used to block the tiny air hole on a plastic fuel can). [Thanks previous owner!] Apparently, everything was fine until the hose split and the screen dropped off. That left the pickup tube exposed and at certain times that plastic cap would drift into the end of it and block the fuel completely. By the way the tank was clean as a whistle, only a little corrosion on the pickup tube. Anyway, I reassembled all and took it out in the pasture and tackled some foot high grass with power to spare. Hope this will help someone in the future and again, thanks much for all your input guys! ....

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2001-05-17          28288

Mike: Always nice to hear when a problem gets solved, and always interesting to hear what the problem actually was. That is one for the books--a correctly diagnosed problem with a truly unpredictable cause. Actually, I suppose a physicist might find some predictability to it, but fixing a tractor is more practical than theoretical. My 'for the book problem' was spending hours on a Triumph M/C that blew fuses unpredictably. Neither the other mechanics nor myself could find the problem or cause the fuse to blow no matter what we tugged or wiggled. I finally found a prediction. The fuse blew when driving downhill and when only the rear break was applied. Having found a prediction, it didn't take too long to find the cause. It was bad wiring where the wiring harness went around the steering crown. Going downhill and applying the rear break only caused a forward weight shift, which spread the forks forward and caused a short. Bring the bike back to the shop, and everything would test OK. Drive it around on the streets and it would be OK. Hit the hill and use both breaks OK. We must have gone through 30 fuses trying to find the problem. Anyway, that's my theory of repairs. If you can predict it, you can find it. Otherwise, you've just got to start putting new parts all around the problem until it goes away. Hope you, me or nobody else actually needs my repair theory in the future. ....

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