# 4020 injector pump issue



## mastrkee (May 8, 2017)

I was mowing when my tractor started slowly loosing rpms. It eventually went to an idle and then died. I changed and bled the system but still couldn’t get her to run. It will fire up and fun for a second and die out like it’s starving for fuel. I left it sitting for a few weeks and when I revisited the project it will run at idle with the throttle pulled back but never much above 8-900 rpm. The lift pump is old but seems to be pumping fuel. What does these symptoms sound like to you fellas? I’d appreciate any input y’all might have. 


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## mastrkee (May 8, 2017)

That was supposed to say that I changed the filters and bled the system. 


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## thepumpguysc (Jan 25, 2015)

Sounds like the classic "flex ring" problem..
Take off the return line at the top of the inj. pump.. now take out the fittings ALL THE WAY DOWN to the aluminum cover & start it up WITHOUT all the fittings & line.. Does it run & rev up??
Clean the fitting out.. it has a ball & spring & gets clogged w/ crap & will shut down an engine..
IF it is a flex ring problem, it'll keep shutting down on ya.. & you need to get the pump repaired.. I can do that for ya.
The 4020's ran 2 different "rossa master" pumps.. a CBC & a JDB.. if its a JDB do as above..


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## mastrkee (May 8, 2017)

thepumpguysc said:


> Sounds like the classic "flex ring" problem..
> Take off the return line at the top of the inj. pump.. now take out the fittings ALL THE WAY DOWN to the aluminum cover & start it up WITHOUT all the fittings & line.. Does it run & rev up??
> Clean the fitting out.. it has a ball & spring & gets clogged w/ crap & will shut down an engine..
> IF it is a flex ring problem, it'll keep shutting down on ya.. & you need to get the pump repaired.. I can do that for ya.
> The 4020's ran 2 different "rossa master" pumps.. a CBC & a JDB.. if its a JDB do as above..



















I’ve taken the input line and fittings out and cleaned the screen in the fitting but not the return line. It’s on the side of the pump and the input is on the top. I’ve attached a couple of pictures for reference. Is there a screen inside the return line of this type pump as well?
Thanks for your reply and for any further information you can offer. 



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## thepumpguysc (Jan 25, 2015)

Yes, its on the "side".. [actually its the top] the brass fitting..


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## mastrkee (May 8, 2017)

Great call on the return line plug. I pulled the line, found the crap you spoke of, cleaned it out, cranked it and ran it with said line removed. Afterwards I put the bush hog back on her and cut for about a hour and she started losing power again just as before. It quit before I could get back to the shop so I pulled the line in the middle of the field, although I didn't see an obvious trash pile, she fire back up and I cut for a couple more hours without incident. 
What is this flex ring you speak of? I still have an issue with the throttle not responding as it should. When I push up to idle she wants to die off so when I pull the throttle down just a little she'll rev way more than the amount of throttle given, WAY MORE! I'm thinking an pump overhaul is in the near future. 
Any more input on the subject?
And BTW thanks a million for helping so much so far!!!


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## thepumpguysc (Jan 25, 2015)

There are a million threads on the subject.. google is your friend on this..
Some sites will tell you its a DIY job.. it IS NOT.. depending on your wrenching skills & experience. There IS an updated part that takes the place of the "plastic" piece, [flex ring].. but it costs extra to buy..
DO NOT run your equipment like it is.. ESPECIALLY w/ the throttle/governor problems.
The broken flex ring will cause the rpms to rise to an UNCONTROLABLE level & you'll end up w/ a run-away condition.. [rod thru the block]..


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## thepumpguysc (Jan 25, 2015)

That pump is easy to pull off..
SHUT OFF the fuel..
disconnect all the lines & linkages..
remove the side cover on the pump, 2 flat head screws, drain..
2 lines under the side cover, 1 is stationary & 1 rotates.. rotate engine until BOTH lines line-up & stop..
Now remove the 2 or 3 nuts holding the pump down & pull up.. DONE


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## mastrkee (May 8, 2017)

I just wanted to give an update. I had a local shop that has worked on my equipment before rebuild my injection pump, had one more round of crap plugging the return line, and now the old girl runs like a champ.


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## lexc269_6243 (Oct 28, 2021)

my son purchased a 4020 that sat for many years we changed filter's provided clean fuel source and can not get fuel to injectors. It'


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## thepumpguysc (Jan 25, 2015)

What r the #’s on the first line of the name plate.??
There are a couple different pumps on the 4020..
It’ll help in diagnosis..


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## lexc269_6243 (Oct 28, 2021)

thepumpguysc said:


> What r the #’s on the first line of the name plate.??
> There are a couple different pumps on the 4020..
> It’ll help in diagnosis..


its a 1295734


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## lexc269_6243 (Oct 28, 2021)

it has fuel coming out the return line port and i removed the solenoid it was varnished a little i freed it up and next i was going to give t 212v and a ground i assume its a pull in and hold.to allow fuel in head


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## thepumpguysc (Jan 25, 2015)

That’s the serial number..
Give me all the #’s..
U can take out the guts of the solenoid and screw it back in..
That way you don’t have to worry about 12v..
If by some black magic it fires off, just back out the low idle screw to shut it down..


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