Power Screw Locking Collar

[TSuter]

I've been wanting to ask this for awhile just been to busy. All the posts I've read about the power screw say that you need to remove the factory locking collar, well on mine I didn't need to. I've turned it in 1. 75 turns and I could probably get another 2 turns before hiting the collar. Question is could someone have turned my screw back previously? With the screw turned in 1. 75 from when I bought the truck, the star wheel bottomed out and the fuel pin turned for max fueling my highest EGT is 1050. The only smoking I do is a light haze at WOT. Boost guage is still awaiting install so I don't have those numbers.



Oh, before you ask the collar is tight.



TIA



Tom

 

[Greenleaf]

It varies amungst individual pumps. I have seen pumps that have about two turns prior to hitting the collar and one pump was still OEM (as best I could tell) and the screw was tight against the collar stop.



If you have THAT much to play with I'd suspect it was turned out. Just a thought. You EGT suggests that you have a pretty lean running engine. For what that's worth.



GL

 

[TSuter]

That's kind of what I was thinking also. Seein as this is my daily driver, what kind of damage could I do by turning the screw in too far? Isn't one of things if I go too far I could get into a runaway condition?



I would only being turning in about a turn at a time so I can keep an eye on the EGT and boost once I get that in.



Tom

 

[Greenleaf]

What will occure if you begin to upset the balance of spring force/weight force is that it will not respond normally. You'll know what I mean if you venture into the realm. Throttle response will change.



I turned my first pump screw in after installing POD's. It was very unresponsive. Most noticable was when the engine was under a light load. again, the action of the pump would be different for individual pumps.



GL

 

[BushWakr - RIP]

It's fairly well know that there are some "lazy pumps" out there... . some will go wacked out on ya with a small tweak and others need a ball peen hammer and serious verbal encouragement to get with the program... . so to speak



The lock collar will tell you if it's been moved ..... look at the firewall end of the collar... if it is nearing the hex head end of the fuel screw or starting to approach the hole in the that screw then it has been moved back. Normally I see about 3 or 4 threads between the back end of the lock collar and the end of the threading on the fuel screw... that is roughly stock location from the factory... .



pb... .

 

[TSuter]

Just went out and looked the locking collar is up against the hex head with no threads showing.



Tom

 

[TSuter]

Ok evidently I have one of those pumps that like the Pastor says needs "a ball peen hammer and serious verbal encouragement to get with the program". I removed the locking collar off the power screw and got half a turn before the screw bottomed out. figured I try it there, started the beast up and it idles about 800 rpm, backed the idle screw out so it isn't touching the striker and she still idles at 800 rpm. I did the crew chief thing and bent the striker just a bit to get her to idle at 700 rpm where she should be.



The pump as it sits right now star wheel all the way down, smoke screw is stock (played with it up and down seems the best there), fuel cone is turned for max fuel, timing is stock, and the power screw is 2. 25 turns in from where it was when I bought the truck. All but the power screw setting have been in this config for awhile now. I'm making 22lbs boost and still only 1000* EGT at WOT.



The question for the pump gurus is did I miss something in the sticky at the top of the page and throw the pump out of wack? Or do I just have a stubborn pump.



The truck runs great, it's just the whole bigger, faster, more thing. On a budget of course



Sorry for the long post



Tom

 

[Greenleaf]

Stubborn pump I suspect. They don't all act alike. Some are very sensitive while some are not... ... ... ... ...



FWIW Next time you adjust the idle speed, try the throttle rod. It's threaded to adjust the length, thus will change the position of the pump's speed control lever.



You may need to adjust the governor high speed screw. If that gives you more rpm's you will have more fuel and heat at the WOT position.



If that works fer yah, then there is the next step to obtain more speed/throttle travel at WOT position... ... ... ... .



Buy or make a custom grind fuel pin.....



Buy the 14mm plunger/modified head... ... ... .



BTW, exactly how much heat do you want????



GL

 

[TSuter]

Just trying to get more out of the pump. Read on here about guys hitting in the 1300 range, I'm only hitting 1000. I know it's not good to hold it in the 1300 range for a period of time, just suspected I was not getting enough fuel.



The high speed screw has been been backed out for awhile too. Forgot about that, and there isn't anymore adjustment I can get out of the throttle linkage. When I say striker I'm probably not calling it right, it's the plate that the idle screw pushes against. right now that plate is hitting the housing for the idle screw.



Tom

 

[Greenleaf]

If your throttle control lever is is going back (in the WOT position)and hitting the pump top you still have more throttle left my grinding off the control arm a bit. I seriously doubt you are getting full travel from the control lever as you would have to use a grinder/cutter to modify the throttle cam. Often we also have to modify the fuel peddle (inside the cab) as the peddle goes to the floor board befor the throttle control lever is maxed in it's movement.



Have you done this?



You didn't mention if you have tried to adjust the throttle rod.



Do you have the old worn out plastic ball joints on the end of the throttle rod?



GL

 

[bgilbert]

Verified full throttle travel at pump? Someone or something pushing the throttle pedal in cab to floor and you watching at the injection pump for full throttle travel? Wouldn't he have a runaway if he has his full fuel screw bottomed out?

 

[BushWakr - RIP]

"... ... . BTW, exactly how much heat do you want????..... ">>>Scott your a baaaaddd boy...



Tom, keep tweaking, you're going to get what you want from it... like I said, some pumps need encouragement is all... . do the pin thing... but for starters, get the fueling response from the pump before you put in other parts... just my thoughts here but I figure there is a bit more performance you can achieve if you follow the suggestions from the guys...

Also take some time to just lean and stare at the pump top, linkage, assembly etc...

When you look close it will start to come into focus on the interrelationships of the parts... throttle rod/adjustable ends, the throttle "cam" has a 90* "pin" that comes up against the inside of the throttle bracket. You need to look kinda under/behind the "cam" to see how the little tab contact the bracket and limits travel.



Remove your AFC housing and look to see if you AFC cone has a "witness mark" on it and if it shows there is travel from the bottom of the cone to the very top were the "throat" is.

If not you're not getting full travel there.....



Another thing to consider is the fuel screw... often, once the collar is removed or backed away the threads of the screw are a bit pooched... this will cause the screw to feel like it is bottoming out... . back out the screw and look at it closely... does it look like that could be happening????

If so, turn it in until you start to feel resistance and then go 1/8 turn... the idea is to go slow here just in case you're actually up against the travel limitations/runaway point.

If you do this, start the engine and let it idle a few seconds, then slowly operate the throttle and raise the RPM... watch as you approach 1500 - 1600 RPM as a "first caution point"... if you hold that throttle position and the engine idle stays steady then slowly continue up to 2000 - 2200 RPM and hesitate a few seconds... if it continues to climb upward then you are close to possible runaway.

I say "possible" because I have found that the governor will eventually grab hold and pull it back... . unless you've really "massaged" some internals...



Give that a try for starters...



pb... .

 

[TSuter]

Thanks for all your help. I forgot the golden rule I try to teach all my trainees K. I. S. S. (Keep It Simple Stupid).



GL, after looking at the linkage, I took that completely out of play and figured out I was missing a litle travel on the idle side and almost 3/8" at WOT. The idle end was caused by the linkage not being adj. right, and the travel at WOT or lack there of was caused when I had put some extra carpet in to preserve the original . After some creative filing and bending I was able to get full travel. I made one run on the way to work, wow what a difference. Before I had to back out for traffic I hit 95mph, 1100* egt, 30 psi boost, at 3000rpm Oo. . Oh, and I do need to get rid of those plastic ball joints. you wouldn't still happen to the part number for the good ones?



PB, I didn't get much of chance to look at the piece you were talking about 'cause it started raining. Once it stops then I can play a little more .



Thanks again



Tom



P. S. I don't always drive like a maniac, but I do like to play with ricers and mustangs once in awhile :-laf .

 

[AlK]

For throttle couplers take a look at the following:



https://www.turbodieselregister.com/forums/showthread.php?t=39994

 

[Greenleaf]

You gotta play with the ricer's and 'stangs time to time. Teach them a lesson. Another favorite is the high-schoolers with the chevy half tons and hot-rod 350 cid.



Bill, the fuel screw in all the way doesn't always result in a run-a-way. I know what your thinking... ... ... ... ... ... better bring that pump back to me for more R&D as opposed to turning the screw. I'd rather work the inside of the pump as opposed to simply turing a screw.



There is a young fellow that lives in town, drives an 89 D250 that told me his pump was maxed out 'cause he dun turned his fuel crew in "all the way". Right, OK then.....



Tom,

Double check to see that the fuel control lever is passing overtop the fuel supply line that enters @ the front of the pump, next to the fuel control lever.



Given all the info, and assuming that you apply it, you'll have a pretty nice running rig. It just takes some time.



GL

 

[TSuter]

Thanks 'preciate all the info, if it wasn't for this place I'd still be driving a stock truck!



Tom