Wow thanks for the responses everyone, will hit you up Josh if I find ours is bad .

Well I've officially started working on it, luckily they had bought a 99 truck FSM so I've been researching. I noticed the TPS (APPS) is a 6 wire deal, what the hecks with that . And I've been looking all through the book but I haven't found how to test and diagnose the APPS. Why 6 wires, I've always seen 3 ?

So I'm guessing the functionality is the APPS sends its signal to the comp which will control the fuel pressure from the high fuel pressure pump changing the fuel volume yes? If the APPS turns out not to be the problem, could the fuel pump have an issue?

3 of the wires are as you would think, a convential potentiometer, The other 3 wires are 2 calibrated position switches, Used for idle validation..IE "idle" and "not idle" , these are for lack of a better term and to keep me from typing a book, watch dogs, in the event of a failure and/or erroneous signal from the position sense to tell the ECU that "hey...the pedal is at idle" so it won`t run away.
Eric You really need to get some sort of scan tool if you don`t have it so you can access the data stream...NOT one of those freeking code readers, you really need to see if the ECU and the FPCM (electronics in the pump) are talking to each other, it will aid greatly in diagnosing such an unknown.
Few know that you can creativly toss 12 volts at a VP with nothing else hooked to it and get it to start and idle, Plus while there is a good possibility that the APPS may be an issue, ALOT of VP "dead pedal" issues stem from the pump electronics itself, especially with 98.5 and 99 model years and without being able to at least access diagnostic codes and data you are shooting blind with expensive parts.
Contrary to "internet" opinon lift pump pressure at this point is a wasted thought, the vane pump in a VP is capable of drawing fuel on it`s own and it will still take throttle, while it won`t be happy for long like that it will run

Just 2 more cents worth

Rick

ok the other 3 are switches... 1 for WOT and idle I guess, what's the third then .

I did some poking around on it today and the harness is pretty hacked up in some places, the harness was from some truck and they clipped some of the unnessesary things and left the rest. They bolted the necessary components to the dyno/motor such as the engine ECM and the PCM.

I did some wiring investigation on the APPS, it seems all but one of the wires runs to the ECU, the other is a sensor ground. That sensor ground ties in with all the other sensor grounds (except the engine speed sensor ground which goes into the ECM) and goes into one of the PCM pins. Well it looks like the previous guy spliced them all together and grounded them to the dyno chassis.

While that is a concern I'm not sure if it would cause the problems we are seeing since they're only grounded in the PCM for accuracy (I think).

Blown - after I run the motor (just cuz I want to see what it is actually doing) and I go through the wiring harness my first step is to borrow my friends Snap-on MODIS to check the TPS and other sensors .

One thing I'm not sure is there is the diagnostic connector tho .

you`ll have to add a diag connector I can just about bet on that unless they did when they hacked the harness, It will have the CAN bus connector on it but thats only usable as a diag aid with the cummins diagnostic software.

The 2 idle validation switches have a common feed, hence 3 wires...

Check the attachment

I`ll PM ya all the stuff you need to do to put a j1962 connector on it

Rick

Was that diagram on the regular FSM? Your helps been invaluable Blown .

Yes
Some early versions of the 99 manual still had the pre 98.5 (P pump) wiring diagram in them with the fuel shut off solenoid and related stuff but no mention of the APPS, it got corrected but both versions are out there ( I used to have both ) so you might want to check yours. There were a bunch of errors in both the 98 and 99 manuals due to the switchover to the 24 valve

Rick

A little update, I poked around at it yesterday and read the previous students report. It's a real wiring mess, I know at least one or two things aren't wired correctly. And in their report they mentioned when they gave the ECM/PCM ignition power it did nothing.

It appears they just hot-wired the pumps to get it to idle to at least show the professors something. I started it up today and like they say, no throttle response. I disconnected the ECU for kicks and it still starts. So obviously the ECU/PCM aren't doing anything and it's just spraying base idle fuel in.... So it looks like I have a major wiring mess to deal with first. After which I may actually find the computers do have the security enabled (which would suck).

While I have it off I'll solder in a diagnostic connector. Does anyone know where I can buy a diagnostic pig-tail?

Well after cleaning the harness and giving it a once over most of it looks ok with the exception of a severed ignition wire (done on purpose by previous guys). So I'm guessing it might have that security check enabled... can you guys give me more info on that, what will it do if enabled, will it start at all? Will I be able to scan it etc?

Ok I got all the wiring squared away and hooked it all back up. Just like they described it just cranks no start, the sensors all have voltage etc just no fuel pump relay juice or grid heaters etc.

I did notice one odd thing, I put a DMM set to continuity test with a audible 'beep' and connected it to ground and the wire that normally goes to the 'wait to start' light on the dash. I figured if it were working correctly I'd see it ground, then go off. Well if you turn it all on the 'wait to start' circuit grounds for about half a second every second as if it were flashing the light . Possibly even more confusing is that once it does this you can turn the ignition off, unplug the PCM etc and it'll keep doing it. It won't stop until you unplug the battery, once you plug it back in it's not on, but as soon as you turn the ignition back on it starts again....

My guess would be it checks for the PCM and I guess is un-happy in some way be it the VTSS or other stuff...

I'd like to know:

1. Does the VTSS only apply to the PCM, IE if I change the PCM will the ECU still have it enabled?

2. Is there ANY way to disable the VTSS in the PCM without replacing it? Any places re-flash them etc?

3. Are the PCM and ECU coded in any way for eachother, IE VIN codes etc. Will a PCM and ECU from different years work together? Any other compatibility stuff I should know?

Some pics for those interested