Tractorman

Sounds like the APPS is performing as it should. As far as reading codes, not all scanners are equal. See if you can borrow a better scanner, or maybe try your local auto parts store for a free scan. How many miles on the truck? When did you take ownership? Has the improper idle symptom been there sine you owned the truck? Do you know what injectors are in the engine and how many miles on them? I assume that there is no tuner hooked up. You mentioned that you think the engine has been replaced - any more information on that? - John

I went back and re-read this thread. If I am understanding correctly, the only problem you are now having is that the engine won't return to a normal idle rpm after the engine has warmed up. Other than that, the engine is performing fine/ Is this correct? Is this still occurring. Have you driven the truck with a scanner monitoring the APPS at idle after the engine has warmed and the engine rpms won't drop back to idle? The scanner should read zero percent at idle, then start reading a small percentage just off idle. The APPS uses an internal idle validation switch that tells the ECM to let the engine idle. When the ECM commands "idle", all other inputs to the ECM are ignored. There is a procedure that involves disconnecting the electrical connector on the VP44's PSG and then jumpering a remote power and ground to the PSG. In your case, if the warm engine idles normally under the jumpered conditons, this would indicate that the VP44 is operating as it should. The link below is for Blue Chip Diesel. It shows various troubleshooting methods for diagnosing the VP44 fuel system. Carefully read steps #2 and #3 for a "No Start" situation. If you perform Step #3 and the engine idles fine after it has warmed, then I would think you can rule out the VP44 as the problem. https://www.bluechipdiesel.com/runningtests Have you checked for DTC's? I asked the question before, but I don't recall reading an answer. Don't give up! - John

Your signature says that your truck is a '99. The wiring diagram that I posted is from my 2002 FSM, but I believe the diagram is correct for a '99. Maybe you can verify. When you used the jumper from the positive battery post to terminal #87 in the relay base, you bypassed the ignition switch, clutch safety switch, starter relay, and the 30 amp fuse in the PDC. Since the symptom remained the same (a single click), you have essentially eliminated all of those components and associated wiring from being the problem. Continue with testing in the manner recommended in my previous post and you will narrow down the problem area even further. - John

Bypass the #87 pin and jumper directly from the battery positive post to the "S" terminal on the starter. If the symptom remains the same, then there can be only one of three potential issues. This is assuming that your batteries are fully charged and are in good operating condition (which they should be). 1. Poor connection / cable from the battery positive post to the starter. 2. Poor connection / cable from the engine block to negative post of battery. 3. There is an internal problem with the replacement starter. - John

I don't know how you are using your meter to check continuity for grounds, but if you are testing using the ohmmeter, then the test results will never be conclusive. All it takes is the connection of one strand of a wire to show good continuity. Performing voltage drop tests under load would provide much better information. You sound like you are comfortable using a multi-meter. Many people that I know who have used multi-meters for a long time have drawn wrong conclusions when using the ohmmeter for testing, or using the voltmeter without an electrical load being applied. Again, it only takes a single wire strand to read continuity or 12 volts. This is one reason I use an incandescent bulb test light for testing circuits - the bulb imposes a small electrical load and will readily dim if the circuit being tested has a fault. Have you tried the jumper test that I recommended? I think this test would be the fastest and most conclusive test to perform. - John

Have you checked the condition of the 30 amp fuse in the PDC? I would make a 10 gauge jumper wire with a terminal connector on one end that will fit into terminal #87 relay base in the PDC. Place the transmission into neutral and set the park brake before doing the next step. Insert that connector into #87 (relay base in PDC) and touch the other end of the jumper wire to the positive post of the battery. If the starter cranks, then you have narrowed down the problem area to be somewhere between the battery connection and the terminal #30 of the starter relay, which would include the 30 amp fuse in the PDC and associated wiring. If it still doesn't crank, I would be looking for a ground issue between the engine block and the battery. - John

Here's the pin out from the 2002 FSM. Let know if this helps. - John

I think you are on the right path. Something worth checking. Is the stock engine block-mounted lift pump still being used? If so, the lift pump will get its power directly from the ECM, not the best decision from an electrical engineering standpoint. Many people have relayed the lift pump using the ECM to trigger the coil of the relay - a much better operation and the relay greatly reduces the electrical load on the ECM. - John

I'll bet that is a powerhouse! - John

Splice #165 is a crimped affair - not the best idea for a quality electrical connection. It is located near the timing gear case on the driver side of the engine. Below is a link to the W-T ground reference mod that would be in your interest to perform. - John

When you saw a consistent 5 volts at the IAT, were you using the black/tan wire for ground, or were providing a remote ground? - John

I have never experienced this, but I have heard of it happening. The general consensus is that a strong static charge builds from the normal operation of the serpentine belt. That static charge discharges periodically near the crank pulley because the crank pulley has the shortest air gap distance to ground. Some have replaced the serpentine belt with a different brand and said that it cured the issue. Others have said that the sparking causes no harm and have done nothing to stop it. - John I don't think it is that simple. The ECM could be putting out a good 5 volt supply, but an erratic ground could make it look like an erratic 5 volt supply. I would try to figure it out - not bypass it. - John

Have you checked for any trouble codes? The oil pressure switch, camshaft position sensor, and the manifold absolute pressure sensor all receive a 5 volt signal from the ECM. Splice #165 (S165) is a through connection for ground for all of these sensors and oil pressure switch. Since voltage is "all over the place" for some of these sensors, I would be checking the source and ground for the 5 volt supply. - John

Does your tuner read fuel pressure - commanded pressure and actual pressure? If so, what is happening with these pressures when the stutter issue occurs? Does the stutter between 1800 rpm and 2100 at any engine load, or a particular engine load? There are people on this site that know more about the common rail fuel system than I do - maybe you will hear from them. Sounds like you know your truck pretty well. Now that you mention operating the truck in the salt belt, I would definitely check wiring and wiring connections to sensors, ECM, frame grounds and body grounds, etc. How about the possibility of bad fuel? Might be worth a fuel filter change which would allow you to inspect the fuel passing through the filter, as well. - John

Have you checked for any DTC's? Is fuel pressure where should be (lift pump pressure)? What are the conditions of your battery cables (including the crossover cable) and battery connections - both positive and negative? You may want to get the tuner completely out of the system to help diagnose. Please give some history about the truck - miles and years you have owned it and what you have done to it, etc. - John

What tire size are you running? - John

That makes sense regarding the 9 cm2 housing and could very well be his problem. - John

What was the engine rpm and boost pressure when the EGT reached 1500°? I presume your observations were done with an empty truck. I am curious as to why the high EGT's. I always thought that the HE351CW turbo was a good upgrade - just what I have read. - John

I agree, the concept seems sound. If the added bearing is centered and well anchored, then it should be beneficial. It seems like you may have the equipment and the skills to do that. Let us know how it turns out if you decide to make the modification. - John

I haven't done your particular job, but I think you have to line up two items - the splined input shaft and the tabs (or cutouts) for the pump. Usually the shaft engages first (could be the opposite), then you need rotate the converter (with no axial pressure) to find the tabs for the pump engagement. Just an educated guess. - John

With stock sized / near stock sized tires and stock suspension height - I say no. I am not sure that there would be any benefit even with bigger tires and raised suspension. I installed a steering brace years ago and I have since removed it. The one thing that bothered me about the steering brace was that there were only two set screws (90° apart) for centering the bearing on the the Pitman shaft. That never made sense to me - it always forced the bearing to one side which in turn forced the Pitman shaft to one side, and the set screws would never stay tight. That did made sense to me. I would think that three set screws at 120° apart would have allowed for accurately centering the bearing and would have kept the set screws tight. - John

Sounds like you have your work cut out for you. Just be patient and correct all of the previous owner's careless wiring. Chances are that there is nothing wrong with the expensive components - just poor electrical connections to them. Let us know when you get the problem resolved. - John

Keep us posted...., - John

To aid in troubleshooting, it may be worth your while to remove the Quadzilla completely from the system for awhile - at least until you get this problem resolved. The Cummins sensors are very reliable. In fact, I still have all of the original sensors in operation on my truck. You said that you were going to check for codes with a Snapon scanner after you put the pump back in. Has that been done? - John

Since all of your codes point to a 5 volt supply issue, I would definitely check out the 5 volt supply and ground. Also, I would check the supply voltage and ground for the ECM and look over the general condition of the electrical system (battery terminals, cross over cable, grounds, etc.) Splice 165 (a problematic splice) is part of the grounding circuit for the ECM and other sensor grounds of the 5v system. Auto Computer Specialists (look in the Vendors section on this site) rebuilds ECMs . New ECMs are not available. Lift pump cycles 1/4 second with key in "run" position, approximately 25 seconds in "bump start" position. Just round numbers. - John