I have a 93 6.5t with the DB2 pump, I was going to turn up the pump and had a question and since the whiz kids on the block for mechanical pumps are over here in the 6.2 forum I thought I would ask here.

Heres the question: By adjusting the fuel metering screw does this only supply more fuel at only full throttle or does it also supply more fuel at partial throttle as well. Anouther way of asking the question is: If the screw is turned to supply lets say 10% more fuel is that only at full throttle or is it at 1/2 throttle as well?

I'm trying to get more low rpm power/torque fuel delivery in the 1600 to 2200rpm range without the throttle going to the floor more, and causing the 4l80e trans to shift down or unlock the TCC (this mostly occurs when I have the truck camper on). It seems that the trans wants to shift down a little easier than I would like it to and its directly related to the distace the throttle pedal travels. I understand there is a TPS sensor on the fuel pump for the 4l80e trans but not familar with its operation enought to even try adjusting it or wheather it would help in preventing down shifting of the trans.

retard the adjustment screw on the advance piston on the bottom of the pump...

changing the fuel screw changes fuel flow at all points from what i've been told.

Correct - the adjustment increases (or decreases) fuel from idle to full throttle, and all points in between.

Adj the screw 1/8th to 1/4 turn clockwise to start - just so you don't get a lot of black smoke under load from standing start.

You may need to reduce idle rpm to compensate.

Try that - then if needed you can rotate the TPS a little to alter shifting pattern, but don't do both at the same time, so you'll have a baseline reference to compare to.

Excellant, thanks for the info grape and gmctd, thats what I was wanting to hear.

So changing the TPS will also change shifting is there proceedure for adjusting the TPS or just turns a little and test. I've attemped searches for how to adjust it but came up with little info.