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John, Thanks a ton for laying that out, i will 100% be doing that. Do you think that would cause my issue? We are supposed to go camping again next weekend and I don’t have a whole lot of time. Two questions I have are I was going through old threads here and saw moparman said for alternator AC noise that .05 is marginal and .10 is failed. I was having .7 with accessories off and .125 with everything on. Is that an issue? I had some other guy tell me that’s totally fine? Also saw a test on blue chip diesel on back probing the APPS and seeing if the voltage increases when the throttle kicks up, they said to route it into the cab and check it while driving with an analog meter. But it’s doing it consistently at idle, that’s something I could check fairly quickly and easily.

Hi, I think i m going to change the MAP sensor to see if there is a change..... If not, there are two solutions that will cost me a lot of money.... send my old vp44 in for rebuild, or change the ecm, or change the torque converter , but I dont know... because honestly I don't see anything that's causing these problems.... it's driving me crazy..... I'm also wondering if my pump is properly calibrated, if so what the symptoms would be, or if an electronic component of the injection pump is defective or burned out ... I am convinced that I installed my injection pump correctly. Because if that were not the case, it would not even start....

This doesn't mean that the APPS is faulty - it just means that there is an output signal at idle when there shouldn't be. Need to know where it is coming from. More troubleshooting needed. Since I don't know what your level of skill is with electricity, I will just start with the basics. Let's say you wanted to check the condition of the crossover cable by using a voltage drop test. First, you would need to understand what would be normal for the test results. There are two batteries (wired in parallel) and a starter on your truck. The starter will draw at least 400 amps when cranking. This means that 200 amps will be supplied by each battery. Consequently, when the starter is operating, the positive and negative cable of the driver side battery and the positive (crossover cable) and negative cables of the passenger side battery will be handling 200 amps each. By design there will always be a voltage drop during the starter operation - there has to be, otherwise current would not flow. The maximum allowable voltage drop in a complete positive circuit is generally .5 volts and in a complete negative circuit is generally .2 volts. The positive circuit has a higher allowable voltage drop because there are usually more switches and connection points than in a negative circuit. Voltage drop measurements can be taken at different points with a voltmeter while the circuit is under an electrical load. Voltage drop tests taken without the circuit under an electrical load will show results that are meaningless. So, back to performing a voltage drop test on the crossover cable. This usually works best using two people. One person will be in the cab and will crank the engine as instructed for a specified period of time. Be sure to be safe - truck in neutral / park and park brake set. Remove the fuel pump relay (in the PDC) for the VP44. This will allow the engine to crank continuously without starting. Set your voltmeter to a manual DC voltage scale of two decimals - example: battery shows 12.67 volts DC on the meter. Do not use the floating scale. Place and hold the positive lead onto the passenger side positive post of the battery (the actual post, not the clamp). Place and hold the negative lead onto the eyelet at the other end of the crossover cable. Your meter should read 0 volts. Instruct the other person to crank the engine for 10 seconds (no interruption). A reading of .1 volts or less indicates that the crossover cable is in very good condition. A reading of .7 volts (for example) would indicate that the cable needs to be replaced. This voltage drop test allows you to see the true condition of the crossover cable while over 200 amps are passing through - a real life situation. John

I didn’t use the starter as load when doing the tests, are you able to explain that? Have you seen many Timbos go bad? All my wiring between APPS and ECM is good. Timbo is maybe just over 2 years old. Thanks for checking that out on yours.

It sounds like you have confirmed that a false signal is being generated in the APPS output circuit. It would stand to reason that the engine rpm's would increase if a signal is present. Back to a previous statement of mine that was meant as a question - are you using the starter for a heavy electrical load when performing your voltage drop tests? By the way, my throttle APPS output always showed zero at idle on the OBDLink scanner. John

I was just checking across the wire from end to end. Honestly I can’t remember which wire it was, I just took pictures of the multimeter readings. I should have recorded it better. And okay sounds great thanks. My readings are zero unless I’m on the throttle, but I did notice the odd time while I’m cruising it dropping out to zero but that could be this scanner, it’s kinda slow and laggy. And then now I’ve noticed it going up when the trucks revving and my foots off the throttle.

@Tweety Bird And I had to get out of here and get some downtime. Extremely stressful to get up every day, looking out the living room window at an entire mess of my shop buried under tons of mud and dirt. It was wonderful to just go out north of McCall, ID for about 4 days. We didn't do anything but rest. Now we have returned home and are going to start making moves to clean up the main house with all the unpacking from moving to my place. Lots to do. Then still need to handle the mess in my driveway of my shop. Here shortly I'm going to post up a Go Fund Me Page and we are going to attempt to start heading towards normal life again some how. Anyone who wishes to help out, I will not turn you down. As for those who just want to send Prayers, thank you, but it doesn't clean up the mess, replace my shop or my tools that were lost. Beast and the RV are up near Upper Payette Lake, Idaho Miss Mollie on her first camping experience.

it seems like it's mostly fuel related issue. You can't obtain the speed you are requesting of the engine. The idle speed is lower. Be aware idle speed will change with coolant temperature, but typically when it's way high, like above 225℉. I've played with a rheostat and varied the resistance of engine coolant to see what it controls. IAT will change the aspect of the timing of the VP44. The higher IAT is much more stable for efficiency. (80 to 140℉) is optimal. I'll keep thinking on this why I'm working here on the site. I'll dig for an answer.

Hi, I installed a Fass 100 lift pump a week ago, with 17 psi pressure. That really strange how it behaves, I have the impression that it is soft, and that it takes 2 seconds for it to react if I have to accelerate, it lacks power.... before it did not do it, even the rpm is slower. before it was at 850, now it is at 750. I wonder if I installed this vp44 correctly.... I think so because otherwise nothing would work, and there would be a code....

What is your lift pump pressure to the injection pump? Optimally, you should see 15 to 17 PSI of fuel pressure to the injection pump. Sounds like it's starving for fuel. Measure this at WOT (Wide Open Throttle) at highway speeds to be sure you have plenty of fuel pressure under heavy demands. Here in Idaho, I just got back from camping up in McCall, Idaho, and it was about 100℉ (37°C) outside for the last few days. Remember, I'm running Beast with a 200℉ Thermostat from a 2012 6.7L Cummins with zero issues, even towing my RV. With my Quadzilla I rarely see above 140℉ fuel temperatures, 175℉ engine oil temperature. The only device capable of failure without codes is the VP44. There is several cases where the VP44 just no longer will fuel properly and just not throw any codes being its consider failed within specifications. Sadly its true. ECM will typically have a series of low/high volt codes and P0606. PCM will typically throw P1698 IIRC. This combo is roughly 17,600 pounds (7,983 kgs) rolling up grades of 7% no issues.

Now it s a summer in my country.... the température is above 40 °C. I dont know if it s a problem, but I feel the truck has less power and cut off again.... My speed uphill is about 90 km/h.... it seems that it does not remain stable and that I need to accelerate to maintain cruising speed.... I don't know what to do anymore.... is the vp44 pump playing tricks, or the torque converter or the ecm or the pcm... now I am really disgusted.... The weird thing is that there are no codes on the engine, nor on the dashboard.... It seems like I'm losing power, and I have to press the pedal harder to accelerate... Really thank you if you could help me....

Glad to see you are performing voltage drop tests. Which wire has the .5 voltage drop? I am assuming that you are using the starter for the load while reading these values. I have a Timbo APPS on my truck. I will test it with my OBDlink LX for behavior at idle when I go to town later, and then report back. John

So weeks ago I did perform some voltage drop tests on a bunch of the cables, a lot were like .1-.2, one was .5 I think. Again truck ran great after having the ECM unplugged and doing all those tests. Then we left to go camping last weekend and of course acted up, really just idled high at 1100 and surged a bit but got us there and was fine on the way home. Went to take it for a ride this morning started increasingly slowly idling higher and higher, kicked back down for a couple minutes then snapped to like 2000 and then I just shut it off. I have been cruising around with scanner on and watching the APPS pid and have noticed with no throttle input I am getting an APPS %, I’ll attatch a picture from this morning when it was acting up and foot wasn’t on the peddle. Tried a APPS reset after it was idling high this morning but that’s when it snapped to 2000 after that. Thinking it has to be electrical the way it can just go away for weeks when I’m messing around in there? Really leaning towards the ECM now.

Cool! John

Looks like you're going to win by default, but also this is really a great photo!

I don't have a fuel pressure gauge, unfortunately. I'll add that to my list.

You should know if you found the problem after letting the truck set for a couple of days. If it fires right up, then I think you have solved the issue. Do you have a fuel pressure in the cab of your truck? John

Maybe. It was very unimpressive to see how long it took to slowly pull the diesel into the pump even just a foot below the inlet of the manifold. I had to lift the gas can up to level with the pump to get it to pull the fuel into the manifold...hence the suspicion that the vanes are not as efficient as they need to be. God forbid I run out of fuel accidentally...I'd have to make 7 trips to the gas station with a 5-gal can to fill the tank enough to get the pump to finally pick up the fuel, LOL.

Why do you think your fuel pump is weak? If, in fact, the water separator was the problem, the symptoms that you had - matched the problem. Once enough air was introduced into the suction side of the pump, the pump would struggle to move fuel because the vanes would have been spinning in air - not fuel. This would especially be problematic if the fuel level was low, as the fuel would have to be lifted higher. During your testing, you loosened the downstream filter to help displace the air, but the lift pump still had a source to draw more air (the water separator). Then, when you corrected that issue, the lift pump still did not have any fuel around the vanes, consequently the lift pump still had some difficulty getting primed. Completely normal. Now that fuel is surrounding the vanes in the lift pump and the air leak is fixed, the lift pump will always be primed and ready to start the engine quickly. I think that your lift pump is fine. John

Well, I think I got it figured out. The water separator filter gasket had a slight imperfection in the rubber, which I believe was causing air to get into the pump and air-lock it while it sat. I didn't get any fuel leaks out of it, and no indication otherwise, but after I replaced that water separator with a new WIX model, the pump primed with a little effort, and it's been fine ever since. I still think my pump is weak, though. I can't imagine a new pump not being able to pull enough vacuum to pull diesel out of a fuel can just below it. Has anyone had their pump apart to inspect the rotors/vanes inside? Are they replaceable separately? Thanks again for all your help in troubleshooting! Very gratefully, NomadDick

Damn that sucks! Sorry to hear ACS is dragging their feet on customer service and a fair turnaround time to get you your ECM back to you.