# Diesel tractor idles won’t accelerate



## Cowpoor (2 mo ago)

2013 LS R4041 Mitsubishi 4 cylinder diesel engine. Won’t accelerate only idles. Linkage is good. Changed the fuel filter, cleared the line from the tank and cleared the tank… don’t know what else it could be. Any ideas are appreciated !!!


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## thedukes (Jan 9, 2022)

Check air cleaner../..mouse nest maybe.

Is this non turbo unit?

Fuel and air is whats needed.

Check vent on fuel cap.


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## Cowpoor (2 mo ago)

New air filters, no turbo fuel cap is good. It was running (accelerating ) fine … got off to close the gate and it just wouldn’t idle up when I got back on. It’s as if the injector pump isn’t producing enough pressure.


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## thepumpguysc (Jan 25, 2015)

Have u tried to run the throttle by hand.? If the throttle moves from stop screw to stop screw, w no change in rpm.. u have pump problems..


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## Bertrrr (Jan 28, 2021)

Look at the linkage at the fuel injection pump, disconnect and move it by hand , Look at the kill switch , it may have partially closed on you. Something is restricting the fuel or air


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## Cowpoor (2 mo ago)

thepumpguysc said:


> Have u tried to run the throttle by hand.? If the throttle moves from stop screw to stop screw, w no change in rpm.. u have pump problems..
> [/QUOTE
> Yes… and no response. Fuel flow is good to the pump but then nada. Kinda what I was thinking but wanted to eliminate every other simple possibility before I pulled the pump. Thank You !!!


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## Cowpoor (2 mo ago)

Bertrrr said:


> Look at the linkage at the fuel injection pump, disconnect and move it by hand , Look at the kill switch , it may have partially closed on you. Something is restricting the fuel or air


Worked the linkage by hand with no response. The kill switch is electric… could it still be stuck ??


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## thepumpguysc (Jan 25, 2015)

Move the throttle to wide open..& hold there..
Now move the manual shut off lever on the top cover SLOWLY until u hear the rpms drop A LITTLE and move it back.
Keep picking away until you get full rpms..
I’m thinking u have a stuck metering valve..


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## Vigo (Oct 8, 2021)

Im ASE Master but no diesel specialist and with that has the whiff of very targeted, good advice that i just don’t understand yet..

What is happening inside the pump when you do that? If it’s a long essay and you’re busy don’t worry about it. But you’ve piqued my interest. Ive studied injection pumps on the internet out of curiosity but never taken any apart yet.


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## Bertrrr (Jan 28, 2021)

Be careful if you pull the injection pump , it is timed sort of like a magneto/ distributor cap on a gasoline engine


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## thepumpguysc (Jan 25, 2015)

Vigo.. the manual shut off is connected by a “bar” to the metering valve..
When the manual shut off is pulled, the bar moves the metering valve to the shut off position..
I’m thinking that the mv is simply stuck..& by moving the shut off little by little, the mv will break free from the low idle position..
It’s worth a try anyway..


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## Vigo (Oct 8, 2021)

Ive unstuck a lot of stuff in my day, so it almost made sense already but that explanation helps. It’s not something i can ‘apply’ right away since i dont have a messed up injection pump in front of me, but if i understand the concept i can probably remember it when i ever do have a need. Thanks for the reply.


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## ttucker375230 (3 mo ago)

If fuel pump has a return line to fuel tank, it is plugged


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## bill ln ne tx (4 mo ago)

Cowpoor said:


> 2013 LS R4041 Mitsubishi 4 cylinder diesel engine. Won’t accelerate only idles. Linkage is good. Changed the fuel filter, cleared the line from the tank and cleared the tank… don’t know what else it could be. Any ideas are appreciated !!!


Check the output pressure leaving the fuel pump. If weak replace the fuel pump. They are $100.00 + cheaper on ebay or Amazon then dealers. I was having the same problem. I also added an additional fuel fiter as it leaves the fuel tank.


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## thepumpguysc (Jan 25, 2015)

How ya making out.??
Does your engine have a supply pump.?? 
u said u cleared the lines and tank.. were they blocked.??
What kind of filter set-up do u have.??
Is it a “spin on” filter.??
Is it the 3 pc set-up.?? with the long bolt holding it all together.??


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## Old Graybeard (1 mo ago)

Just had something like this with a Kubota, hooked up an electric fuel pump from a clean bucket of Diesel directly to the fuel filter before the fuel injection pump, problem went away, Looked like the machine was basically running off the injection pump , idle ok but could not do much else without the fuel pump working. Installed new fuel pump and fixed the problem.


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## thepumpguysc (Jan 25, 2015)

it take WAY WAY less fuel to low idle an engine than to run it.


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## dirtscratcher (3 mo ago)

Does it have rubber or steel fuel supply lines to the injecter pump? My old Oliver 1550 has rubber, and it delaminated internally, and was sucking closed. Baffled me for a while, but I finally figured it out.


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## Cowpoor (2 mo ago)

thepumpguysc said:


> How ya making out.??
> Does your engine have a supply pump.??
> u said u cleared the lines and tank.. were they blocked.??
> What kind of filter set-up do u have.??
> ...


Thank you for your responses !! to answer your questions.... The motor is a Mitzubishi S4Q2. no supply pump, the filter is a screw-on filter with water trap in the bottom. The part the filter screws onto has a primer pump on the top. The lines and tank weren't clogged however I did find some algae and trach in the fuel tank so I just went ahead and pressure washed it out. I even pulled the lines from the injectors to see if compression gas from the cylinders was blowing back indicating the injectors are stuck open...but no air blowing back through them. Ran it without air filters for a second with no improvement. I have removed the injector pump and taken it to an injector / pump repair shop. Now it's a waiting game.


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## thepumpguysc (Jan 25, 2015)

If u had sent it to me, we wouldn’t be waiting..
Good luck.


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