4020 destroker screw

lka

Member
I just picked up an early '70 4020 diesel that is a bit of a hard starter in mild fall weather, a bit worried about how it will be with 2 feet of snow on the ground. Planning on adding a manual destroker screw but from reading threads there are a bunch of different part numbers depending on model, year and pump (original vs replacement).

This is the underside and top of my pump. I assume circled is the pressure adjustment? And red arrow is where the destroker would be installed? And the serial tag makes this a replacement "metric" pump.

As best I can tell, the correct part number would be AR96625 for a T-style screw?

Thanks and cheers.

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The drawing shows the typical location of a riveted-on aluminum serial number plate.

Your photo shows a casting number or date code that was cast in when the housing was made, NOT a ''serial plate''.

So I think you have an original pump and need destroker # AR33249 which now subs to individual parts.

And, yes, the screw on the bottom of the pump valve housing is the pressure adjustment.
 
(quoted from post at 12:06:35 09/29/23) Would be a good time to install a frost plug or circulating tank heater also if it does not have one. :D

It does have a JD tank heater and it seems to draw current so hopefully it works!
 

Another option for engine starting aid is an electric operated de-stroking screw. JD part # is RE40463 but at $784.125 there must be a cheaper aftermarket version.
 
(quoted from post at 11:20:47 09/29/23)

The drawing shows the typical location of a riveted-on aluminum serial number plate.

Your photo shows a casting number or date code that was cast in when the housing was made, NOT a ''serial plate''.

So I think you have an original pump and need destroker # AR33249 which now subs to individual parts.

And, yes, the screw on the bottom of the pump valve housing is the pressure adjustment.

Thank you!! I will note that I have no good way to see if there is a serial plate on the pump in that location without removing it, because visibility is miserable. JD's parts catolog says AR33249 is for starting serial numbers less than 201 (mine is 223). Are there other ways to differentiate the pumps?

This post was edited by lka on 09/29/2023 at 01:55 pm.
 
The hole in the pump where they screw in
changed in size over the years. Can you
remove the small plug and determine it's
size and TPI? I have a couple of
destrokers to compare it to.
 
(quoted from post at 14:33:36 09/29/23)
Smaller fitting o-ring ID is .468" & thickness: .078" Later style pump with serial # o-ring ID is .755" & thickness: .097"

Thank you gentlemen I will pull it off and measure. Confirming: It would be the smaller of the two bolts on the top of the pump, the one I marked with an arrow, which is directly opposite the pressure adjustment?

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Open the screen on the left side pf the tractor. The destroke screw is on the left side of the pump, direction of travel. The best way to determine if you have a non-serial pump or a serial pump (metric) is to see if your pump has the adapter called out in item #9 in the second picture.


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(quoted from post at 12:50:07 09/30/23) Just jiggle the steering wheel as you start it and save yourself a lot of trouble...

Yes, the steering wheel trick works, but the destroke screw works a whole lot better! What's better than the destoke screw? The electric destroke like I have on all my tractors. The electric destroke saves batteries and starters.
 

Do you have access to acquiring aftermarket the solenoid & brass fitting that JD offers for the high price of $784.15 for electric pump de-stroker? Several months ago someone on this forum stated they had located these needed parts from an aftermarket supplier but I can't remember which member it was.
 
(quoted from post at 16:40:33 09/30/23)
Do you have access to acquiring aftermarket the solenoid & brass fitting that JD offers for the high price of $784.15 for electric pump de-stroker? Several months ago someone on this forum stated they had located these needed parts from an aftermarket supplier but I can't remember which member it was.

That would of been me. I also shared pictures of the setup on my 4020
 

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