have you ever seen the inside of an vp44?? or a schematic??
There is absolutely no electronic control of individual cylinders.
There are two electronic selenoids on a vp , one for timing one for fuel quanity care to explain which one of those is dropping individual cylinders??

 

my 2 cents, but if it's a rotary pump and somehow the scan tool can fire the solinoid once at the exact same time to open the fuel port and shut down the injection pressure to the injector, that could feasibly "turn off" that cylinder. As long as the scanner can fire on that cylinder consistantly.

Make sense anyone
Eric

 

Inside the VP44 is three radial plungers that work together to create the high pressure fuel pulse. This pulse will happen once with every two revolutions of the crankshaft because the VP44 turns at half crankshaft speed. At the back of the pump is the rotary distributor that is responsible for directing the fuel pulse to the proper cylinder. The electronically controlled dump solenoid is used to limit the amount of fuel injected by opening and bleeding off fuel. This dump valve is controlled by the fuel computer located on top of the VP and gets its commands from the ECM. To disable a cylinder a signal is sent to the ECM instructing it to open the dump valve for one of the cylinders. The high pressure fuel pulse now simply dumps and cannot generate enough pressure to inject. This signal happens each time the fuel distributor comes around to that cylinder.

Hope that helps.

 

won't say that theory is impossible but that would mean the pump is dumping the injection pressure and rebuilding it by the next cylinder firing event which would only be 120 degrees of crank rotation and 60 degrees of pump rotation, that would be one very busy selenoid!! also the vp44 is mechanically timed pump hence the specific key for each pump, where is the electronic mechanism that is going to identify a particular cylinder and cut the fuel to only that cylinder??

 

In a 6 cylinder 4 stroke diesel engine, fuel is injected once every 120 degrees of crank rotation. If the engine is at red line, 3400 RPM or 56.7 revolutions per second, the dump solenoid is fired once every 0.006 seconds. Yes, it is busy.

Static pump timing is set using the pump key and is precisely calibrated by the key offset. Dynamic timing is controlled by the timing solenoid. Here is a link that will explain most of the workings of the VP.

http://www.dodgeram.org/tech/dsl/ISB/Vp44.htm

 

[SIZE="3"][FONT="Times New Roman"] The one gent commented about being able to run the engine with out the electonics of the engine working it is called a " Breakout Box" They used it on mine and could only tell that the engine started so It wasn't any good to fix the factory problem of my truck! Mine did pound very heavly driving it home when it was new from Prince George in late 1998. The only thing that has been close was the locomotive engines injecting 10% more fuel in for a number of cycles for testing reasons.

I guess that the injectors were POP tested? ( 4500 psi) It is funny to read the problems that people are having now with what I went throught when the truck was new!

 

bent valves i understand how the vp44 works but no where in that post or link is there anything that tells how the pump could electronically identify a particular cylinder, and then cut the fuel electronically to said cylinder?

 

The ECM is “all knowing” on which cylinder is being injected. On my early ISB engine the crankshaft tone wheel tells the ECM where to inject fuel. Later trucks, model year 2000 + I think, did not use the crankshaft but switched to the camshaft sensor. These signals are used for a coarse setting to get the engine started. Built inside the VP44 is the precise timing tone wheel that is also used to indicate TDC of cylinder 1. The ECM can now disable the injection event because the VP is locked to the crankshaft rotation by the gears.
I have never seen the cylinder drop out test done and I doubt it will work at high engine speeds. At idle and low speed the time it takes for the ECM to do its magic is not a problem.

 

I have done a cylinder drop test with the DRBlll. I only used the test at idle.