Power screw adjustment...

[Gary - K7GLD]

I've already adjusted my stock power screw to the maximum travel available with the limiting collar still attached - didn't actually get more than a quarter turn outta the adjustment before hitting the stop, back when I installed my banks stuff years ago.



NOW, I'm interested in additional adjustment for a little more power - but drawings and text on the subject are a bit vague as to exactly HOW to remove the collar to permit additional travel of the adjustment screw. Text with the photos indicate the screw/assembly should be removed carefully as to not lose the current adjustment positioning of the screw, and the collar removed - but are unclear as to exactly WHAT ALL it is that is to be removed? OR, how to remove it...



All I can see in the drawings, and in the limited view I can get on the pump itself on my truck, is the screw with collar attached, and the locking nut - is there something ELSE down there outta sight that must be loosened or unscrewed that permits the whole power screw assembly to removed as a unit?



AND, what seems to be the most commonly accepted amount of increase for lightly modded trucks like mine without objectional side effects - like vast smokescreens and poor fuel economy?

 

[Dave Carter]

Originally posted by Gary - KJ6Q

I've already adjusted my stock power screw to the maximum travel available with the limiting collar still attached - didn't actually get more than a quarter turn outta the adjustment before hitting the stop, back when I installed my banks stuff years ago.



NOW, I'm interested in additional adjustment for a little more power - but drawings and text on the subject are a bit vague as to exactly HOW to remove the collar to permit additional travel of the adjustment screw. Text with the photos indicate the screw/assembly should be removed carefully as to not lose the current adjustment positioning of the screw, and the collar removed - but are unclear as to exactly WHAT ALL it is that is to be removed? OR, how to remove it...



All I can see in the drawings, and in the limited view I can get on the pump itself on my truck, is the screw with collar attached, and the locking nut - is there something ELSE down there outta sight that must be loosened or unscrewed that permits the whole power screw assembly to removed as a unit?



AND, what seems to be the most commonly accepted amount of increase for lightly modded trucks like mine without objectional side effects - like vast smokescreens and poor fuel economy?

What I did Gary. I loosened the power screw. Then backed the locking nut out to the collar. Then removed the power screw from the pump Took another nut nad locked the nut to the scew. then removed the collar. This way you have the original settings when you go to reinstall the power screw. Hope this will help you.



Dave-- W7aul

 

[Gary - K7GLD]

"What I did Gary. I loosened the power screw. "



Did you loosen the SCREW, or the LOCK NUT?



"Then backed the locking nut out to the collar. "



HOW do you get the lock nut out to the collar, without totally losing track of the original setting? Of course, in MY case, the lock nut is ALREADY up against the collar - so that may not be an issue... And I'm assuming the existing lock nut is free to turn IN on the screw as far as you want - and is only limited in travel in the OUTWARD adjustment by the collar? SO, I'm again assuming you merely loosen the lock nut, and then simply UNthread the power screw and lock nut outta the pump as a unit?



"Then removed the power screw from the pump Took another nut nad locked the nut to the scew. "



You mean you threaded another lock nut BELOW (pump side) the existing lock nut? If you place a SECOND lock nut on the TOPSIDE of the screw, you would be tightening it AGAINST the TOPSIDE of the very collar you're TRYING to remove! I'm not trying to be intentionally dense, honest - I just wanna make DERN sure I understand the procedure before I get started!



"then removed the collar. This way you have the original settings when you go to reinstall the power screw. "



IF I'm correct, and you placed the temporary lock nut BELOW the original one AFTER removing the power screw and lock nut, in order to next remove the collar, I *assume* you would then have to carefully REMOVE the temporary nut from from its position BELOW the original nut, and transfer it to up ABOVE the original lock nut to where to collar USED to be (since there is no longer the collar to hold/restrict screw movement) to temporarily secure the screw while threading it back into the pump?



"Hope this will help you. "



WELLL-L-L...



What I *think* you're trying to tell me, is that ONLY the lock nut and power screw (WITH its collar) are removed as a unit - but I'm not real certain as to what holds the setting of the power screw in relation to the lock nut WHILE it's being removed - it's REAL tight and awkward in that spot, and looks REAL easy to screw things up if yer not careful and attentive!



ALSO, it looks to me, if I was correct in my assumptions above, that you COULD go ahead and make your initial RE-adjustment to the power screw in relation to the existing lock nut while you have it out of the pump, and then tighten it in place with the newly added secondary lock nut - and THEN all you need do is thread the whole assembly back into place and tighten it down?



If you have done the removal and subsequent tweak in setting, how much did you turn yours, and with what result? Are you happy with the adjustment?



OH, and as for what *I* have already done to my pump, as stated above, I maxed out the factory setting on the power screw, opened (turned clockwise) the Star Wheel 1/4 turn and rotated the diaphram by 1/4 turn clockwise as well. Little more smoke - noticeably more power - but now with the propane injection, I think I can use a bit more fuel in full-throttle pulling situations...

 

[Gary - K7GLD]

AS it turns out, ya gotta loosen the locknut - and ASSUMING you have already screwed the power screw in as far as it will go (after all, that IS the reason for this chore, to get MORE adjustment range on the power setting... ), you simply continue unscrewing the locknut and attached screw outta the injector pump - careful of the included metal, and fiber washers that comes with them - and also be careful to not damage the small O ring that seals the power screw inside the pump and is retained in a groove in the power screw shaft.



Once out, CAREFULLY thread the locknut down away from the collar, counting the turns, as far as it will go before being stopped at the unthreaded shoulder down further on the screw - mine was a tad over 6 full turns from its maxed out setting, down to the shoulder - yours may vary, and DO count carefully, and write the turns down for future reference so you don't forget! Keep in mind that this is a fairly sensitive adjustment, and even a quarter turn can make a big difference!



NEXT, ya gotta remove the metal collar that is spot welded onto the power screw, and limits its travel - I used a bench grinder on mine, and CAREFULLY ground thru the spot welds JUST until I started seeing signs of screw threads showing - I then used pliers to break off the collar, which now came off easily. I fortunately had the forethought to buy both a couple of metric locknuts, AND a thread die, since I figured the thread on the screw body was bound to get somewhat damaged in removing the collar - I was right, so I used the die to clean up the threads.



Once the threads were back in good shape, I took one of the new metric lock nuts, and threaded it down towards the stock locknut to about where I figured my new screw setting would be when I reinstalled the screw into the pump - I decided to open mine up another half turn from the previous setting. I then carefully counted the turns as I threaded the original locknut back up to its former location, plus the additional half turn I had decided on, and then carefully locked the 2 nuts together - I now had a single secure assembly for reinstallation back into the pump.



Reassembly was a snap - nothing could move or get outta whack on reassembly - all I had to do was thread it back in as a single unit and tighten it down! I started the truck, and immediately noticed my idle speed had increased somewhat - nice, since it had been a tad too low before, and the engine was idling smoother as well. A quick test drive showed that I have a pretty decent smoke trail for the first 50 feet or so of hard accelleration - then it backs down to a haze as turbo boost comes up - the launch from dead stop is significantly stronger than before, and even with a 3. 07 differential and the US Gear unit in OD, it's REAL easy to break the rear wheels loose - and I have 2 tool/fuel boxes and a 5th wheel hitch in the back for ballast!



Only a full-blown test pulling a load in the hills will tell the whole story - but so far, it looks GREAT!



I'd be real interested in hearing from others who have done this to see if my amount of adjustment increase is in line with what others have done - and to also hear if power increases from opening up the power screw are restricted to high - or low end, or evenly applied across the full RPM range of the Cummins... Also interested in what this will likely do to EGT's in long hard pulls, and if maximum boost is affected in any way?