I messed with that screw and ended up regretting it. Basically it affects the throttle sensitivity in the throttle travel range. In one direction, the truck will power up sooner in the begining of the pedal range, in the other direction you will have to press the pedal harder to get the same fuel flow to the injectors. When you combine this with the timing curve of the injector pump (Which will not automatically change to stay in synch with this setting), its not hard to get the settings far out of wack if you are not careful. It may not damage the engine, but it probably won't run as well. Keep detailed notes of every change you make so going back to the original settings is possible.

In the case of an E4OD tranny, having the engine make more torque at a lower TPS signal voltage will cause any transmission slip to get worse. I managed to get mine back to about where it should be, but I don't remember which way does what. 1/4 turn in either direction is enough to have a noticable effect so its not hard to figure out.

If you have to remove the top injector pump cover, then care needs to be taken when reinstalling it. If you get it wrong, the engine will not start, or I hear it could cause a runaway on the other extreme. I personally only experienced a no start condition.

 

There is no fuel adjustment screw on my IP. The mechanic went in and ( thru the top of the IP) and supposedly gave me 1 flat or 60 degrees. When I got there and we went for a ride I still had a max of 5 lbs of boost under full throttle. So with me watching and with him under protest, he turned it up another 50 degrees or almost another flat. On the second test ride i had more power and maybe 7 lbs boost max. However I now am getting some black smoke, so I'm getting a little more fuel than it needs. I have mixed emotions about the black smoke, I prefer to have no smoke and also my EGT's have increased slightly. Today under heavy acceleration I saw 1000 degrees, but as soon as i backed off a little it dropped to 600 degrees. My mechanic thinks my boost guage might not be accurate, Its an Autometer guage with a small plastic lind feeding it boost. He says the line looks too small.

Again the truck runs great, I know the power is over 200hp, and the mechanic thinks so too. I may live with the smoke or I can back off the IP the last 50 degrees. Right now I can shift into 5th gear at about 45 mph and accelerate. I have very tall gearing, 3:55 rear. So 45 mph is about 1500 rpm.

Thanks to everyone for all the helpful comments.
john

 

me i would leave the smoke, but thats just my opinion i just love black smoke

 

The external fuel screw does not change the fuel delivery quantity.

What it does is affect where the fuel delivery is increased related to RPM.
Turning the screw out lowers the RPM where the IP starts to inject more fuel, so some people call it the torque screw.

Adjusting the fuel regulator pressure also changes the timing curve and can get you all messed up if you don't have the right equipment to check the timing through the RPM range.

The cold start timing advance works by increasing the fuel pressure inside the IP when the engine is cold.