# FIsher MM1, Wont Lift Plow! Need Help



## Hebert_chj (Dec 19, 2008)

Hey guys, Heres the deal. I have a 2000 GMC K2500 6.5 turbo Diesel with an 8ft fisher MM1, plow. Fluid changed twice yea with good aftermarket fluid. About week ago I hooked up and plow went up about half way and then stopped and I saw smoke coming out from under the hood. Once I replaced the electric motor and solenoid in the firewall the plow worked again. It angles left and right great but will only lift plow about 1/2 inch off ground. I take chains off and the ram goes all the way to the top. I sit on the triangle and it doesn't come back down till I someone hits the down level. Almost positive its a hydraulic problem but don't know where to begin. Any help would be greatly appreciate. Don't have funds to bring to shop and accounts need 2 be taken care of.


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## russ130 (Oct 29, 2002)

What is happening when it stops lifting? Does it just stop with no more noise? Does it still make pump noise just no movement? Does it smoke? When you lift the ram with no plow can you stop it by applying pressure to the triangle?


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## no lead (Dec 10, 2008)

sounds like the pump is weak. will it angle in the down position? or up? , have someone lift the blade while you lift the plow. will it go up? if it wont lift but angles fine the pump is weak. turn pressure up on pump. pull motor, looking down on pump it is a 7/16 head plug. turn it 1/4 turn and put the motor on and lift. better? if no then turn 1/4 more and try again. don't turn it in much more than 1and1/2 turns. it will bottom out.


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## Hebert_chj (Dec 19, 2008)

The motor I replaced on the plow when it blew has terminals that are top and bottom. The previous two motors that were on the plow had terminals side by side. Don't know it the two motors are the same or if they have different rpm levels. The plow angles both down and when I jack it up the and hit the up level the plow stays up and angles great. When I hit up level when plow is on the ground you can hear the solenoid click and the motor make normal humming noises. It just doesnt seem to have the power to lift my 8ft plow. Have never had problems like this before. Any information would be greatful.


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## no lead (Dec 10, 2008)

did you adjust the pump?


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## Hebert_chj (Dec 19, 2008)

I am currently out of state for the hoilday and wont be home for a couple more days. When I go to adjust the pump what exactly am I looking down at for the adjustment screw. you say remove the motor if the screw in the vavle manifold or directly on the topside of the pump itself where the shaft faces vertical? Im fairly familar with the Insta-Act system and the setup on my 8ft HD series MM1. Id really hate to bring it to the fisher dealer considering I have been a certifed Auto mechanic for close to ten years.


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## sven_502 (Nov 1, 2008)

I had the same problem with my western unimount, it wouldnt lift hardly half way, then just progressively less than that from there, losing power each time, but itd still angle when half way up or so. It ended up being there was no proper ground for the plow motor, it was grounded to the second battery that hadnt been grounded properly.


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## Hebert_chj (Dec 19, 2008)

*Wiring*

This is my third season Ive owned the truck and used the plow. Ive gone over all the wiring on the whole unit and truck and everything looks up to par. One thing I forgot to mention was last year at the end of the season the plow didnt work very well. Was real choppy and wasnt working properly. When I took it apart in september to change the suction filter I found the suction tube and filter laying in the bottom of the fluid reservior. Im wondering if I might have blown some seals in the pump from using it at the end of last season with no suction tube attached. I know I had a seized motor which cooked my firewall solenoid but after replacing them I thought it would work again. Does anyone know where to buy a rebuilt pump? Ive found the pump kit for my plow fisher part #21501k but its close to $250. I hate to just throw parts at it and hope it works, especially when they are so expensive and Im on a fixed income. Thanks for all the help guys.


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