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7790 Not Behaving


mswyka

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My 7790 has developed a lazy streak. It starts fine and runs fine for about 15 to 20 minutes then it loses power and generally won't rev past a high idle. Fuel filters are new (spin on can and in line can) and transfer pump screen is clean. Transfer pump appears to be building pressure, although I noticed on inspection that there is a tear in the uppermost layer of the transfer pump diaphram. No fuel leakage is noted from the pump drain port. I don't know much about diesels and could use some help in understanding what to look at. Mark?
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Look for a good fuel flow problem. A piece of trash in the tank floating around will block the tank outlet and cause this problem. It shuts off and the suction releases it to float around untill you run it again and it repeats. There could be other problems also, but this is a simple thing of cleaning the tank out. Hope this is all it is.
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Drain and clean the fuel tank. Microbes grow in old fuel and float in the fuel and will in a few min clog the outlet screen. Also change the air Filter and precleaner
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Good thoughts. Air cleaner is new. I will clean out tank and let you know what happens. Any suggestions regarding where to get parts for the Lombardini? My local Simplicity dealer does not stock any parts for these engines.
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  • 2 weeks later...
It is a blessing that I have other tractors, that way, even if I need to do an investigation or a repair I can do it in my own sweet time. Such is the case here, I removed the tank, drained the fuel and discovered the black slime hair balls that must have been clogging the pick-up in the tank. Black crud removed, pick up screen cleaned and re-shaped and it looks like we are back in business. Thanks for the advise. Mark
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The black slime sounds like what was in our backhoe when we got it. We cleaned the tank as best that we could without removing it but the slime kept coming back. We asked a a local farm tractor repair center, they said diseal fuel can get a fungus in it that will come back if not treated. The fungus usually grows in fuel that has been setting for a long period of time, but they have also seen it in daily run machines. For about $20 they sold us an additive for the fuel that would kill it. This only requires a small amount added to each gallon of fuel. I can check what it is called if you would like to know. It sure fixed our problem. Dan
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Diesel Kleen in the gray bottle is supposed to keep it away. http://www.powerservice.com/dieselkleen_cetane_B_ind.asp They also have Bio Kleen Diesel Fuel Biocide to clean it up, and 911 in the red bottle. I usually use the grey in the summer and white bottle antigel stuff in the winter. I am so glad you got your 7790 running well again!
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