3020 - 4020 pencil injectors

8850dave

Member
The Stanadyne part #20494 is the replacement for AR 50781 which I thought was for side console tractors, but AR69289 were what I sold and used for many years for the early 3020-4020s with the pencil injectors. So now the dealers seem to sell only the 20494 injector so is that the right one and will it work fine??
 
The main difference is the cracking pressure setting which can easily be changed. Any new injector should be checked anyway as some are no good when new or are set incorrectly.
 
Deere used at least 8 different injector nozzles in 3020 and 4020 tractors just from Stanadyne. They vary by the amount of spray holes (some have four and some have five. 4 holers were .012" and 5 holers were .011" Also the sac-hole sizes differed. Also opening pressure differed. Stanadyne # 20494 is a sub for them all. Subs for 18270, 18241, 18646, 18660, 18767, 20364, and 20518. Main thing is to just get the opening pressures even as possible. A new injectror (not so-called rebuilt) is expected to drop in pressure by 200-300 PSI once it is used for awhile so is expected to be set higher then used or "rebuilt" injectors.
 
Earliest pencils had longer tips and smaller pipes w/no chopper.
The design was changed several times. Latest versions were probably
developed after 4020 were no longer made.
 

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