which is correct

[jtate]

ok here is the deal, i have a 85 6.9 and a 92 7.3. i know that both ip's are the same for both. there is a difference between the two that i noticed today. on the ip shaft there is a cam that rotates when you give it fuel, it pushes on the arm that changes the timing on the bottom of the pump. i noticed that on the 85 ip you have to give it a little throttle before it even starts to push in on the timing advance piston, now on the 92 as soon as you give it fuel it pushes on the rod and i think that it is even pushing in on the advance at idle. which one is right and which one is wrong? and if there is a way to adjust it how is the correct procedure?

[M.L.S.C.]

Yes, there is a way to adjust it - on the side of the IP there's the VRV on the '85 and the FIPL on the '92, between those doodats and the body of the IP itself there's a little side-eccentric cam-thingie - you loosen the set screw on that and turn it and increase or decrease the delay before activating the lever arm.

[jtate]

Originally Posted by M.L.S.C.

Yes, there is a way to adjust it - on the side of the IP there's the VRV on the '85 and the FIPL on the '92, between those doodats and the body of the IP itself there's a little side-eccentric cam-thingie - you loosen the set screw on that and turn it and increase or decrease the delay before activating the lever arm.

thanks m.l.s.c for the responce. i have another question about the adjustment, is it supposed to push in on the advance as soon as you move the throttle or build up some rpm's before it pushes it?

[M.L.S.C.]

You know, that I'm not sure of, I have mine set so it acts almost immediately off idle - my logic behind that is since that's the cold advance, and tis actuated directly by the throttle shaft, the fast idle solenoid can only move the throttle lever travel so much, so if I 'delay' the cold advance then I won't get the maximum advance the pump is capable of.

[LMJD]

- my logic behind that is since that's the cold advance, and tis actuated directly by the throttle shaft, .......

First of all, that's not the cold advance it's the light load advance piston, secondly, it retards timing as the rocker pushes the piston in when more throttle is applied.

[cdnsarguy]

You may have 2 totally different engines.....what does the 92 truck data label state for year of build...... the label is on the timing/oil filler cover, year should be punched out.

I would consider they were set to specs for each engine at the IP rebuilder/builder if OEM.

[M.L.S.C.]

Originally Posted by LMJD

First of all, that's not the cold advance it's the light load advance piston, secondly, it retards timing as the rocker pushes the piston in when more throttle is applied.

Mkay then, so I guess I want its action delayed a bit then? Right now tis where you tap on the throttle slightly and it starts moving the lever arm, how should it be set? I mostly drive empty, at speed of about 50-55mph.

[LMJD]

Mkay then, so I guess I want its action delayed a bit then?

It's not an adjustment you screw around with in the driveway or advise others to do so either. It's correctly set when a pump is calibrated on a test stand at an injection pump shop. On the other side of the piston there's internal IP transfer pump pressure acting on one end of the servo advance piston. The position of the servo advance valve in the piston bore regulates and determines the degree of advance you get at any throttle setting or load. That's the condensed version.

[M.L.S.C.]

I figured as much, however the pump on my engine is of an unknown origin, has been messed with by the previous owner, and that whole cam-thing was a bit loose on the shaft to begin with - would you suggest keeping it as is, thus reducing the amount of advance I have a bit from where it probably should be, is safer for the engine? Compared to messing with it, and likely ending up over-advancing it?

Dunno if it matters, but truck runs great right now, with plenty of power (or so it seems), and pulls 15mpg with a 2000-lbs enclosed trailer, and around 20mpg when empty.

[jtate]

yes its definetly two different engines, ones a 6.9 and the other is a 7.3. but as far as i know they both use the same pump. i havent adjusted anything on the pump, just wanted to know why there was such a big difference in the setting between the both.