Tractorman

Exactly what I would expect. The voltage will bump to above 12 volts with the engine running and voltage at the battery rises to around 14 volts. You could try taking apart the lift pump. I have heard that there can be problems with the relief valve ball and spring - both with Air Dog and FASS. John

Set up your inhibiting tool again and cover the end of the tail pipe with your gloved hand (or block of wood) to see if you can feel a cylinder miss. Do the test with the inhibitor on and with it off. Actually, do three tests - inhibitor on, inhibitor off (within the first 10 seconds), and then with the inhibitor off after the noise returns. If there is a miss, you should be able to tell if it is random, multiple cylinders, or just one cylinder. I am just trying to think of ways to get some useful information. I agree that even though it sounds mechanical, why does the sound go away when certain conditions are met? I wouldn't rule out either a timing knock or something mechanical at this point. What about that tone ring? Were you able to perform a complete inspection of the whole tone ring? John

But, you can check the voltage at the pump with the pump running. Just probe the wire at the connector and connect the positive lead of you meter. Connect the other lead to the same ground used by the pump. I would expect to see right at 12 volts (maybe slightly less) with the ignition key on, lift pump running, and engine not running. If you see significantly less voltage, then either you have a poor electrical connection, or you have a lift pump that is drawing an abnormal amount of current. I see that there are two fuel filters with your FASS system. Is one a strainer and the other a filter, or are they both downstream filters? Is it possible for one to be plugged? Just covering all bases. John

The lift pump should last longer, unless it was starving for fuel. I have a used FASS fuel pump DRP-02 (less than 100 gph) on my truck that has been on the truck for over nine years and over 150,000 miles and it is still working fine. Did you check the voltage of the supply wire with a meter while you were pump from the 5 gallon container? You would want to make sure the power and ground circuit for the pump is functioning properly before you condemn the lift pump. Even if the pump had operational problems, the suction line should have been full of fuel - unless, since there was only about 5 gallons of fuel in the tank, the fuel in the suction line may have just flowed back into the tank as soon as you broke the seal of the fitting. John

This is definitely a most unusual problem. I have listened to your video many times. The sound seems mechanical to me, but I can't think of any mechanical issue that would behave the way it does when you inhibit a cylinder and then reactivate the cylinder, or that the sound would go away when the ECM is removed from the loop. Also, the sound is rythmic, like it is only affecting one cylinder. I don't know if any of this is true, but this is what I keep coming back to. Have you partially blocked the exhaust to see if there is a steady miss when the sound is occurring? Have you removed the valve cover to see if anything unusual is happening - with or without the engine running? Can you detect if there is a cylinder miss when the sound is occurring? Gotta figure this one out! John

First, I must commend you for a well written description of the symptoms of a problem that you are trying to resolve. People rarely give that attention to detail when describing a symptom or communicating the order of what they have done to resolve the issue. Well done! So, it is interesting that the noise goes away completely with the VP44 running on its own (no ECM communication) and then when the ECM is back in operation, the delayed return of the sound after you inhibit any single cylinder. I don't have the answer, but the fellow you referred to in the above quote may be on to something here. The VP44 has an internal encoder that replicates and compares the crank / cam sensor signal, which could explain why the noise is gone when the ECM is out of the loop (the VP44 no longer needs the crank / cam sensor). And, maybe, when you inhibit a cylinder there is a delay in the knock returning possibly because the timing shifted from the internal encoder to the crank / cam sensor? Just speculating here. Another very good possibility is that if your truck uses a crank sensor, the ring on the flywheel that triggers the sensor may be loose, cracked, or partly missing. John

I have not experienced your situation, but from what I have read from related past postings on this site, you are in need of a rebuilt ECM. The ECM basically will not boot up, or won't finish booting up, so no engine start. John

Don't have any answers, just waiting to see what the APPS reset offers. It will be interesting to see if the Quadzilla is the culprit. John

If you don't mind a few questions after you have had some time in the seat, I would like to know a few things regarding transmission converter lockup / exhaust brake operation under certain driving conditions. Enjoy the truck - I'm sure it is going tow effortlessly. John

Just read this. I would imagine that Mark thought that the end of his world had arrived when that event happened. I'm glad to hear that he didn't suffer any major injuries, or worse. I cannot offer any immediate help for the next two weeks, but after that, let me know if there is something that I can do. I do have a small excavator (about 3500 lbs and it has a thumb) and a dump trailer that I could use to work through the debris, but the excavator would not be able to handle large rocks - say, over 500 lbs. I could scoot some bigger rocks around, just won't be able to lift them. Is your house in any danger of a similar slide? John

Good to hear you are back up and running. Good timing to reseal the vacuum pump and the side cover. I would be very interested in hearing your thoughts regarding the 2025 Ram 8 spd transmission after you drive it for awhile. Are using the new Ram for your upcoming trip? John

An air intake leak on a diesel powered engine of this era will not affect engine idle or cause the engine to die. This is because fuel is directly injected into the engine cylinder - the engine won't care where the air came from. An intake leak could cause poor performance under load because of loss of boost and it will allow unfiltered air to enter the engine which can cause engine damage over time. An air intake leak on a gasoline powered engine will affect engine idle or cause the engine to die because the leak would alter the air to fuel ratio in the intake manifold. John

That would be the one. I still have all of the original positive cables and ground cables on my truck. Periodically, I perform a voltage drop test (using the starter as a load) and I check each circuit individually. In my opinion, a voltage drop test is the best way to determine if an electrical circuit is in good condition. It is conclusive and never lies, and it stops you from wasting time and spending money on unneeded parts. The best part is that you don't have to take anything apart to perform the test, which is really the way you want to do it - actual circuit operation in real time, nothing disturbed. I am also using the OEM alternator (a Bosch). No matter which alternator you use, there is always some AC ripple. Good batteries and good wiring practices absorb that ripple to the point it does not interfere with electronic devices. I have had a few conversations with W-T (a very knowledge man when it comes electricity). The primary reason he installed a Nations alternator was because it uses twice the number of diodes. That was important to him because he is an avid ham radio operator and he really needed clean electrical circuits. He even took apart his lift pump (the worst contributor of electrical noise) and added components to filter the noise. Personally, I wouldn't go to the expense of the Mechman alternator and wiring kit - I would just perform the voltage drop tests and replace any cable or clean any connection that showed excessive voltage drop. John

First, I misinterpreted your numbers. I thought they were readings in the whole number and decimal form. I see now that they are the wire number and a reading in decimal form. Those numbers are good. Yes, these are the relevant wires. The DTC that was set referred to the Idle Validation circuit. As I was typing, you were replying. The wiring circuit looks to be good. Did you re-check Splice #165 for a proper ground (from Pin # 11 on the ECM)? I suspect that the symptoms will resurface. John

If you checking just the wiring harness only (APPS and ECM both disconnected), those readings should be around 1 ohm or less. Did you verify for accurate readings by testing your leads on your multi-meter first? John

I checked Rock Auto and I see that they are genuine Bosch OEM injectors. I don't think the problem is injectors. You do need to get this figured out as you don't want your wife to have to spend too much time in a ravine with an old Beetle. John

My wife and I will be returning from a local camping trip on Friday, June 6. If your trip to Baker City will put you here after June 6th, you are invited to our house and you could stay in a private camp site with water and electrical hookups. You could then tour the areas that you want to see at your leisure. We would be happy to meet a member of the forum and help out if we can. Think it over - you can private message anytime you want. I also have been turning wrenches most of my life, and have a shop and plenty of tools should they be needed. John

They are stock OEM injectors - correct? John

Only 128,000 miles on the truck? What year is the truck? The fuel pump relay that I am referring to is for the VP44 injection pump. It supplies power directly to the fuel solenoid inside the VP44. It is labeled "Fuel Pump" or "Fuel Pump Relay" and it is located in the PDC. The OEM lift pumps are not relayed - they receive power directly from the ECM. I am the original owner of my truck. I started having problems with the VP44 (P2016 code) at 65,000 miles. A year later at 87,000 miles, I had the VP44 replaced under warranty. Additionally, a relayed lift pump was fitted into the fuel tank, also covered under warranty. I have since logged over 310,000 miles on the re-manufactured VP44. Also, worth mentioning is that for the last 310,000 miles, lift pump pressure has never been over 12 psi and usually averages about 5-6 psi, so lift pump pressure really has never been causing the problems with the VP44. Assuming your VP44 has failed and you are running the original VP44, there really is / was nothing you were going to be able to do to make your VP44 last longer. There was a lot of misconceptions regarding the VP44 injection pump failures in the early years and those misconceptions have carried on through the years. The lift pump was the least of the problems, or not even a problem at all. Bosch recognized that there were issues with the early VP44's. Some of those were: rotors not de-burred properly during manufacturing resulting in rotor seizure, poor solder connections in the PSG, under-designed diaphragm for absorbing high frequency pulses, metallurgy problems with timing piston / bore, to name a few. The good part is that Bosch corrected all of those issues with many revisions during their VP44 re-manufacturing process. Unfortunately, other re-builders became involved, but did not necessarily follow through with the Bosch updates. That resulted in casting a continued dark shadow over the VP44 injection pump reliability. From an authorized Bosch re-builder, the Bosch re-manufactured pump comes with a new PSG calibrated to the pump. The combined unit is operated on the Bosch 815 test stand for three or four hours of rigorous testing. This is the pump you want to buy. They have proven to be reliable. John

Well, dang! Did you get good life out of the pump? Those three codes narrow things down a bit. By chance, did you try swapping the VP44 pump relay with another like relay? Doesn't cost anything to check. John

I think he said that he did a road force balance on all of the rear tires. John

The VP44 trucks were only made from '98.5 - '02. There could be a discrepancy in some wiring colors, but not likely. Just pick a row that looks like the colors match the pinout row and you will know right away whether or not you are on track. For example, if the LB/BK wire APPS signal from the ECM pin #25 was a different color than the diagram, then the wire will be the same color where it connects to pin #3 on APPS connector. Just be patient - it will begin to make sense. John

That's always a bit confusing to me, as well. I verify by identifying some of the wire colors on the wire connector side to match them with the pin number. This will confirm the orientation for identifying the correct pin number. John

Shown below are the pinouts for the ECM. Perform continuity tests (using the ohmmeter setting) on circuits that you wish to check. Be sure there is NO POWER supplied to any circuit being tested. For example, the APPS communicates only with the ECM. You could perform continuity tests on all of the connecting wires (see bottom photo). John