4020 - Injector Cracking Pressure

Planning on testing the pencil style injectors(AR50781) from our '65 4020 (S/N ______ - 200,999) today.

I believe our I & T manual specifies 2750 PSI cracking pressure but just wanted to confirm?

TIA

2700 for new injectors

Thanks SV!

It looks like the literature that you posted for the opening pressure adjustment applies to the large body / rebuildable style injectors as it mentions the use of shims.

The RoosaMaster / Stanadyne injectors have a threaded sleeve for adjusting opening pressure.......

(quoted from post at 16:51:36 01/27/20) 2700 for new injectors

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A question to the diesel / injection repair gurus, can anything be done to remedy RoosaMaster / Stanadyne pencil injectors that don't chatter properly?

Only 3 out of the 12 injectors I tested break & chatter crisply. The rest simply dribble / pi$$ fuel out once opening pressure is reached. As an FYI, opening pressure on those njectors varied between 2600 to 3000 PSI.

During testing I made sure to actuate the hand pump sharply more than a few times to flush out any possible contaminants & seat the needle with no improvement in break or chatter quality. If I cycled the hand pump ridiculously fast I could make them chatter but not at all if I stuck to the 30 - 60 strokes cycle speed.

After thinking about it 6 of the 12 injectors were old ones that I had laying around and were likely removed in a rough manner using pry bars as I don't have the proper slide hammer puller. The other 6 injectors I just removed from a tractor and they came out easy as some thoughtful fellow had liberally applied anti-seize during installation. LOL

I'm assuming I should probably write off the 6 injectors that were removed using pry bars? What about the others that came out easy? Can anything be done?

Your welcome . The manual gives instruction on
regrinding the needle and seat but you have to
special tools to do it so probably not much you can
do . I didn?t think of that about the the pressure
adjustment i can get the right instruction if you need
me to

That's OK.

I've got an OEM 3020 service manual in addition to the I & T shop manual(JD-29) and both state roughly the same pressure settings for the RoosaMaster injectors: 2600 PSI +/- (with old spring) & 2800 PSI +/-(using new spring/new injector)

I ended up setting the 3 injectors that had good chatter to 2650 PSI and readjusted their needle lift to 1/2 turn out from bottomed. They still break & chatter crisply so they'll go on the shelf as spares & I'll order a new set for the ol' 4020.


I don't have the extractor tool needed for lapping the needle/seat but that's neither here nor there as most of the injectors aren't actually leaking that bad from the tip, most of them just aren't chattering properly.

(quoted from post at 12:07:02 01/28/20) Your welcome . The manual gives instruction on
regrinding the needle and seat but you have to
special tools to do it so probably not much you can
do . I didn?t think of that about the the pressure
adjustment i can get the right instruction if you need
me to

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Stanadyne JD 20494 pencil injectors for 3020 and 4020, NEW setting 3200 +- 50 PSI, used 3000 +- 50 PSI. Lift setting 3/4 turn.

Thanks for the info.!

Do those settings apply to all vintages of 4020 using the Stanadyne 20494 / JD AR50781 injectors?

Is there a noticeable difference in engine operation with those increased settings?

(quoted from post at 14:18:48 01/28/20) Stanadyne JD 20494 pencil injectors for 3020 and 4020, NEW setting 3200 +- 50 PSI, used 3000 +- 50 PSI. Lift setting 3/4 turn.

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Those specs are for the 20494 pencil injector, which replaces at least three or four previous pencil injector numbers. If I recall one or two earlier pencil injectors had five holes, while the 20494 has four holes. I doubt you would see any difference at 300 PSI spread. On IH Ambac 17MM shim type injectors for example, new spec if I recall is 3500-3650 PSI, service manual says DO NOT reset unless opening pressure is below 2900 PSI. Most used injector spring settings allow up to ten percent drop from new spring setting.

Thanks for the info.!

That sheds a little light on subject. The 6 injectors that came out of the tractor have 4 hole nozzles and are definitely the AR50781 P/N(we kept the old boxes from when we installed them). The other 6 injectors that I had laying around all have 5 hole nozzles but not 100% sure on the part number now.......

Long story short, it is the 4 hole nozzle injectors that I was able to salvage so would it be best to set them at 3000 PSI & 3/4 turn lift?

(quoted from post at 09:04:45 01/29/20) Those specs are for the 20494 pencil injector, which replaces at least three or four previous pencil injector numbers. If I recall one or two earlier pencil injectors had five holes, while the 20494 has four holes. I doubt you would see any difference at 300 PSI spread. On IH Ambac 17MM shim type injectors for example, new spec if I recall is 3500-3650 PSI, service manual says DO NOT reset unless opening pressure is below 2900 PSI. Most used injector spring settings allow up to ten percent drop from new spring setting.

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Just finished speaking with a diesel shop on prices for new injectors & thought I'd ask their opinion on the settings. They suggested sticking with the older / lower specs. of 2600 PSI as starting may be improved due to a slight advance in timing that would come with the lower opening pressure.


Thoughts?

(quoted from post at 09:28:18 01/29/20) Thanks for the info.!

That sheds a little light on subject. The 6 injectors that came out of the tractor have 4 hole nozzles and are definitely the AR50781 P/N(we kept the old boxes from when we installed them). The other 6 injectors that I had laying around all have 5 hole nozzles but not 100% sure on the part number now.......

Long story short, it is the 4 hole nozzle injectors that I was able to salvage so would it be best to set them at 3000 PSI & 3/4 turn lift?

(quoted from post at 09:04:45 01/29/20) Those specs are for the 20494 pencil injector, which replaces at least three or four previous pencil injector numbers. If I recall one or two earlier pencil injectors had five holes, while the 20494 has four holes. I doubt you would see any difference at 300 PSI spread. On IH Ambac 17MM shim type injectors for example, new spec if I recall is 3500-3650 PSI, service manual says DO NOT reset unless opening pressure is below 2900 PSI. Most used injector spring settings allow up to ten percent drop from new spring setting.

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/quote]

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First off, you want to RETARD timing to help with cold starting, not advance timing. You won't see any difference in 200 PSI anyway UNLESS the injection pump hydraulic head is worn, and engine starts hard when hot. I found six pencil injectors used in the 3020 and 4020 previous to the 20494 with replaces all of them. 16170, 17705, 18270, 18421, 18646, and 18767. The first three had five holes, set 2800 new and 2600 used spring. 18421 and 18646 had four holes, new 3000 and used 2800 PSI settings. 18767 and 20494 four holes, 3200 new and 3000 used PSI settings. All had lift set at 3/4 turn.

Good day,


Just wanted to confirm before I toss these pencil injectors in the scrap bin whether there is anything that can be done to remedy the lack of a crisp break & chatter?

As an FYI, in a futile attempt I pumped a fair bit Howes fuel conditioner through each of them cycling the handle sharply thinking it might help but to no avail. It did however help to clean out the tips as I noticed quite a bit of black / carbon debris in the bucket I held under the injectors during testing.

(quoted from post at 06:40:31 01/28/20) A question to the diesel / injection repair gurus, can anything be done to remedy RoosaMaster / Stanadyne pencil injectors that don't chatter properly?

Only 3 out of the 12 injectors I tested break & chatter crisply. The rest simply dribble / pi$$ fuel out once opening pressure is reached.

Click to expand...