Technical question about the P7100

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I've asked a handful of people about the two screws on the back of the P7100. There under a plate that is wired shut take it off, and inside under that plate is two screws a upper and lower screw. I've heard don't mess with them, or go ahead give them a turn, I've also heard top one is for fuel, bottom one is for Torque or bottom end. What do I believe, I hope the famous Joe Donelly or Piers can help us undervalvers again on this subject. It seems to me that those two screw control a vulcrum lever, or just a lever BUT what do they do how much or how little do we turn them?? ANYBODY??

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94' 2500 4x4, 2. 5" Skyjacker, tweaked afc & pump, BIG plate, no muffler or resonator, 16. 5x9. 75 Weld Rims, 33x12. 50 BFG Mud Terrians, 60 psi boost gauge, pryometer, J&J Stainless Steel rear 10" drop bumper w/backup lights, Westin pushbar, PIAA 90 Pro series lights, Weatherguard toolbox 27"

 

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SmokinCummins
If they are under plate that you have to unsrew to take off. These are probably related to governor springs.
On the other hand if they out in the open just hard to reach High idle screw is horizontal and low idle screw is vertical.
The throttle linkage is linked to these.
Check archives plenty of post on both High, Low set screws and Governor springs.
Matter of fact I'm going to check myself seem to me there is one more thing you can turn its related to turbo boost.

 

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SmokinCummins,

You have found the magic screw!!! The top screw is to set the amount of rack travel. By turning this screw in, you increase the amount of fuel you are going to get at a given trottle lever position. CAUTION: If you are going to turn this screw in, be careful!!! Turning it a little bit makes a big difference. For reference: the total rack travel of the P7100 Pump is 21mm. The 180HP rating (auto) has a RT of 13. 85mm while the 215 (manual) has a RT of 14. 45mm. As you can see, that is only a difference of . 6mm (in other words, NOT MUCH!!). I am not sure what the treads per inch are of that screw, but you can probably see by the above, that turning it slightly can make a big difference. Just be careful or you will have lots of smoke and lots of heat (high EGT!!!).

The lower screw is to adjust the riding angle for the rocker. The rocker is the lever that rides on the fuel plate at max throttle position. This is the device that transfers the shape of the fuel plate face to the fuel rack. If you change the position of this rocker, you will change the shape of your torque curve and thus the shape of your power curve. How much or little your curve shapes change depends on the shape of the face of the fuel plate.

There is a lot more technical discussion that could go with the above two subjects. For what most people want, turning the top screw is the way to go. This will give you more fuel=torque=power across the entire throttle range. Like I said before... ... . just BE CAREFUL!!!! And don't get too greedy the first time you adjust that screw. I will be doing mine when time allows. I plan on using a paint marker to mark the original position of the screw and nut. From there, I can play all I want. Only difficult part is that the back of the pump is not exactly easy to get to and work on.

Good Luck.

Matt Pelton

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'96 Auto, Reg Cab, 4X4, SLT, Line-X, Rancho 9000's, Dunlop Radial Rover 33X12. 5's

 

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thanks matt very well discussed lots of info thanks for all the info it helped alot. I'll get them 24 valvers one of these days!!


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94' 2500 4x4, 2. 5" Skyjacker, tweaked afc & pump, BIG plate, no muffler or resonator, 16. 5x9. 75 Weld Rims, 33x12. 50 BFG Mud Terrians, 60 psi boost gauge, pryometer, J&J Stainless Steel rear 10" drop bumper w/backup lights, Westin pushbar, PIAA 90 Pro series lights, Weatherguard toolbox 27"

 

[Archive]

I suggest you make your adjustments via torque plate and not try to "optimize" those screws. It will be much easier to get what performance improvement you want and to go back if you want to do so. The torque plate can be used to conrol total rack travel and the shape of the TST plates is designed to match the stock setting of the rocker height adjustment.

The most fruitful things for your pump, imho, are (1) TST plate; (2) injectors; (3) governor spring kit. If you have a 160 hp pump and go to 370 marine injectors, add the high flow delivery valves. Adjusting some things on the pump turn out to be like tar babies--you just get stuck in deeper--you never get quite satisfied and the more you mess with them the more it seems you have to, just to get back to what you had in the first place. As hard as those screws are to get to, I'd much rather custom grind a torque plate to get the same kind of change.

[This message has been edited by Joseph Donnelly (edited 10-12-2000). ]

 

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Went looking for screws and plate today. Found it, actually seen before but since they had tamper wire twisted thru them never gave them second thought.
Was looking for possible fuel line leaks(fuel or air) think I found some. Engine cranks and runs OK, just rpm at idle is low when first fires up. If I rev it up over 1000 rpm or drive down the road first stop I come to, it idles at 825 where it usually does. Also mileage is a little lower than I like for highway driving.
Low rpm at idle symptom seems to be air entering fuel lines.
Lower fuel highway fuel mileage seems to be fuel leak. Great in city miealge 19. 5 average.

 

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MPELTON1

Do you know what the total rack travel is for the 230 rating?

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97 SLT 2500, 5sp, 3:54, 285/16, US Gear Under-drive, BD Hx40-16cm, BD 370 injectors, TST #10 plate, BD full 4" exhaust, Centerforce Clutch, BD Governor Kit, and a few other items with a lot more on the shelve!