Well I'm getting involved in my schools (Cal Poly Pomona) I.C engines lab. They received a donated 99 cummins 24 valve motor from Banks performance to use as a dyno mule for students senior projects. 2 students already did their project on assembling it, adding an air-water aftercooler and hooking it up to one of our dyno's.

They didn't get too far on it because of a dyno issue (pump is from the 50's), they got it idling but said they could open the throttle and the motor would just continue idling basically . They're running just the stock 99 truck injection setup, ECU and all. I'm basically picking up where they left off, I know basically nothing about diesels but I can work my way around EFI pretty well. So anyone have any ideas where to start looking. I assume this system uses some type of OBDII setup yes? Where can I get a good scanner/logger?

Sounds like my 99 cummins did. All of a sudden it wouldnt rev anymore. It was the throttle position sensor. Might not be the same for you. But the voltage wasnt right so wot it didnt even respond

That's what they came up with too, seems weird but I don't know how diesel EFI works yet...

Yep..Most likely you have a APPS issue (pedal position sensor) if the ECM sees is out of range it will default to idle for safety reasons.

Ok cool, they also mentioned that it may be because the security check (from the key). In my experience that shuts down the car completely though... could it be it dis-ables the TPS on this model truck?

What would you guys suggest for tuning/data logging?

Thanks blown . Do you know of any FSM's I can download online for trouble shooting?

Eric
There may be, but since I have all that on hand I honestly have never looked elsewhere to know for sure.

Hopefully someone else can answer that.

Good luck with it

Rick

check throttle position sensor thats what happened to my friends diesel you could push throttle and it would only idle. hope this helps

The rack is also known to stick in those pumps thanx to low sulphur diesel fuel. A buddy of mine was about to replace the pump on his 98 because it was unresponsive to input from the peddle occasionally. Did all the sensor stuff still acted up. He got in touch with a company that remans these pumps locally and was told that about 75% of the pumps he remans really had nothing more than the rack stuck on them. His cure that seems to be working so far is a little outboard motor oil added to the fuel occasionally. Your results of course may vary.

Kevin

HUH ?

The rack is what all the plungers are controlled by which in turn controls fuel. On a non electronic pump the throttle was connected to the rack mechanically. On an electronic pump the ECM controls a stepper motor which in turn moves the rack to add or subtract fuel. The stepper motor has way less power than your foot so if it gets gummed up at all it don't move.

Kevin

Some day when you are bored, take the time to look up how a VP44 actually works.


Rick

I have a good apps sensor from a 2000 . let me know if you need it I will donate it.

Well that is how it was explained to me. I have seen the inside of a few 3406 Cat injector pumps and because they use plunger and barrels with individual fuel lines I assumed the VP44 used a similar arrangement. I saw no reason to doubt what I was told. How the pump works not withstanding, once he added some lubricity to the fuel with the outboard motor oil it quit with the nothing happens when you step on the peddle routine.

If you could post a link to some internal pics and info on a VP44 I promise I won't wait 'till I'm bored to educate myself on its operation.

Kevin

I was sure the pump in my buddies truck had 6 lines in a row on top. It's a 1998 24V IIRC and it's electronic because he has an Edge box on it. If it has the pump in the link on it I obviously did not know from whence I spoke. Thanks for the link.

Kevin

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