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4020 rpm varys up -down-not responsive

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byron

07-26-2002 04:34:04




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4020 fuel problem? rpm varys up & down. i'm going to try new filters today ,seems like its starving for fuel ---maybe fuel pump




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JDJIM

07-26-2002 09:09:03




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 Re: 4020 rpm varys up -down-not responsive in reply to byron, 07-26-2002 04:34:04  
Could be the governor weight retainer ring , they eventually come apart , it's a plastic piece that holds them together it wears out and the pieces start floating around and eventually pluggs the return line . Good way to check it is lossen or disconnect the return line that's the one from the pump that goes up to connect with the injector leak off lines and then returns to the top of the fuel tank . With this line loose or disconnected see how it runs . Anyway the pump has to be removed and taken apart . They make a new style weight retainer assembly that is one piece and doesn't have the plastic part . I put one in my 3020 a few months ago . I had the same problem . The new weight retainer and the gasket kit for the pump was somewhere around $75-80 . I took it apart myself , I guess I'm cheap , they wanted around $475-500 for a rebuilt pump I thought for an old extra tractor I'd try it myself , it works and runs like new .
As mentioned before when you remove the pump MAKE sure all the marks are lined up and time it to the TDC mark on the flywheel .

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Paul

07-26-2002 06:52:10




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 Re: 4020 rpm varys up -down-not responsive in reply to byron, 07-26-2002 04:34:04  
I've had about 6 of this style pump go bad all had govoner problems all still ran. and all did about what you are describing.and all took about $400 to fix.Paul



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Spoker

07-26-2002 04:52:15




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 Re: 4020 rpm varys up -down-not responsive in reply to byron, 07-26-2002 04:34:04  
Does it do it more at full throttle? If so the Injection pump might be the problem. If the filters do not work, remove the injection pump and have it rebuilt.



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byron

07-26-2002 05:20:56




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 Re: Re: 4020 rpm varys up -down-not responsive in reply to Spoker, 07-26-2002 04:52:15  
it varys at all speeds-could it be dirty air filter -starving for air? did'nt ck yet



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Spoker

07-26-2002 05:37:10




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 Re: Re: Re: 4020 rpm varys up -down-not responsive in reply to byron, 07-26-2002 05:20:56  
Bet you will find that the problem will be the injection pump. I do not think the air filter will cause this surging problem. Yeah I know you do not want it to be the injection pump. It is a Rousamaster Pump and are not cheap to work on. If you take it off be sure to bring #1 up on compression and the marks in the little window on the side of the punp( remove to screws on the window) are lined up prior to removing the pump.

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John de Marrais

07-26-2002 19:34:55




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 Re: Re: Re: Re: 4020 rpm varys up -down-not responsive in reply to Spoker, 07-26-2002 05:37:10  
A few comments about the fuel system. You didn't mention if it's an early or late 4020. Many early models did NOT have an injection pump with a weight-retaining ring mentioned by others. The early round Roosa Master CB pumps had no ring; the later JDB Roosa Master pumps do. The latter style, when the ring comes apart, will plug the housing-pressure check-valve (where your return fuel line hooks up). So, to check for this problem you need to unhook the line and also remove the check-valve (the brass fitting the line was hooked to). Another way you can usually tell is to pull the little timing window off the pump (two screws). If you see a bunch of junk in the there that kind of looks like mouse turds - than the ring has come apart. Anyway, it would behoove you to check the entire fuel system for blockage or air leaks. If you can see into your fuel filter, look for air bubbles when the tractor is running. Also make sure the fitting/shut-valve in the bottom of the fuel tank is not plugged. Also check the fuel pump by CRANKING the engine - do not check it with the hand primer. Quite often the internal linkage in the pump is worn where it runs off the engine's camshaft and will not work well when driven by the engine but will pump fine when the hand-primer is used. As others mentioned, if the weight-retaining ring is bad the pump can be fixed for $60-$80 in parts. Some JD-B pumps need a special wrench to remove the cam-ring stub. If the pump is pulled apart the return-fuel check valve should be cleaned or replaced, and the fuel transfer-pump regulating valve needs to be updated since it will probably be blown apart. It's a simple fix and the parts for the update come in the gasket-kit. Basically a metal bushing is driven into the regulating vavle in place of a rubber plug (in the back of the injection pump).

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Keith

07-26-2002 08:38:48




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 Re: Re: Re: Re: 4020 rpm varys up -down-not responsive in reply to Spoker, 07-26-2002 05:37:10  
And don't forget to wire the throttle wide open before pulling it from the shaft to keep the governor weights from falling.



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