I know there are a million of these posts on here but I just wanted to hear it straight from the horses mouth specifically about my problem.


I am not sure what consists of true dead pedaling, I would assume it means the pedal can go straight to the floor and nothing happen. I am having an intermittent problem, when I am driving around I let off the accelerator and go to say make a turn step back on the accelerator and I have a brief period where nothing happens. It has seriously worried me a couple times because I get just far enough in to the next lane to be right in front of on coming traffic and then I have that second where the accelerator does nothing for me, then it comes back to life. It doesn't necessarily go to the for before it comes back to life. It is more like a dead spot in the pedal than a "dead pedal." It is an extened hesitation when I hit the acclerator. I have been reading about the APPS sensor and wonder if that could be it but I am also having a fueling problem. I have a fp gauge and my fuel pressure is nowhere near what everything says it should be. No load cruising stays around 7-8 psi. Accelerating drops to around 5 psi, and WOT can drop to 1 psi. I have taken it in to a Dodge dealership and they say the lift pump passes their volume test and say that nothing is wrong, I personally say bull hockey. I have replaced my fuel filter within the last 4500 miles and the day I replaced it I checked all my readings again and they all stayed the same. By the way my FP gauge is between the lp and the ip. I used a T connection to go in line. Could this be causing me to get false readings as opposed to say using a banjo bolt connection? I don't have any codes popping up on my odometer when I do the three turns, and I haven't got a code reader to check if any others are actually on my truck.

Everything I have is in my signature and I am still under warranty (83k) and would like to resolve this issue before I drop out of warranty. Any suggestions will be appreciated, and if further information is required to help anyone resolve this problem I will gladly provide it to help this process along. Thank you.

 

Sound exactly like an APPS going dead. You will not have a dead spot in the pedal from a bad lift pump. A bad lift pump will limit Hp. The dealership has already eliminated the lift pump by diagnoses. Tell them exactly what you just explained about being in traffic and turning. If they do not want to change out your APPS under warranty tell them you want it doucumented that you were there for dead spot in accellerator pedal on one of their letter heads.

 

With those low pressure readings on a Vp44 I would do some thing about the lift pump also. Be careful about what you do as adding anything but a factory lift pump will void your warranty. You could buy one from cummins for alot less. If you can not find one for around $150.00 or less PM me I will let you know were you can.

 

Sounds exactly like your apps.

You could get a dead spot here or there LONG before you actually get the dreaded dead pedal. And i don't believe the CEL will come on until many months after you notice the little dead spot in the throttle. i think mine was a slight dead spot (only when I was turning left and accellerating) for a whole year before anything got any worse, then i got the full dead pedal a couple times and CEL and all of that.

 

Sounds like mine was right before I took it to the dealer showing the P0216! New LP and a VP44 later I was on my way. (68,000 miles)


I did an APPS reset in my driveway two days before I took it in, It made no difference.

Is this the OEM lift pump on there now? (If not, do you know the fuel system's history?)

 

By the way,
I got one question???
Does a VP44 get all that hot during operation if you are just putting along and not towing or WOT or any of that stuff????? I find it hard to believe that they can get hot enough to actually wear faster than normal. I am inclined to believe that it is poor lubrication mostly, and not too much heat.... Because they are not exactly bolted to the exhaust or anything like that. I wished I knew more about them.

 

It is the OEM lift pump.

 

Interesting thought. I would ask you what causes heat in moving items? (read lack of lubrication). The thing is that the pump is cooled by the fuel, of which the unused portion is sent back to the tank via the return line.

Take a 105* day in AZ. Now, on a 1/4 tank you are taking fuel that has already been sitting in a tank with an ambient temp of about 100*, run it through a high pressure pump, in an engine compartment that is probably close to 200*+, return it to the tank and start over again.

"Hot" is a relative term. There have been guys that used the infared type thermometers to check out the surface temps on the pump, can't remember at the moment what they were. Also, this past summer was viscious on VP's, about 15 people lost thiers in a matter of three weeks. Makes me wonder. I know the LP is effected by colder fuel, what effect does outright HOT fuel have on the pumps and their operation?

 

I'm in the coatings industry. WE use high pressure and low pressure pumps all the time.

In nearly all cases, a pump will not get overly hot unless there are valves or other parts in it that are already failing. I know that the VP44 must be a little different.

I've never seen a schematic of a VP44, and I realize that it does need diesel to lube it. But I am very curious to see a tech. drawing of one. DOes anyone have one???or seen one???

I knew a mechanic who had a powerstroke (a few years back) that the injector pump quit, and he dismantled the pump himself because he wanted to see what the hell would fail.. He said it was a pain getting it apart, but worth it... It was an O-ring or plastic washer that failed.......and it was never put in correctly to start with (half in the slot and half out or something like that, so it was going to have a failure no matter what,).
I wonder how much of that stuff goes on with the almighty VP44. I'd like to think it's fundamentally a better pump than the ones on powerstrokes and duramaxes. But at one point someone said that chevy and caterpillar were in talks about supplying diesel motors. Maybe they know that it won't take much to own the diesel pickup market.

 

Someone here posted a link to the "other" site, back when you could read all of the threads, not just the initial post. It is a pretty complicated little pump, gave me a half a' headache just looking at the exploded view.
It was during a discussion about a cooling fan or heat sink or something.

 

P.J. good point about heat, this is why running tank low on fuel can/will have adverse effect on LP and/or VP44. Because if there is not enough fuel in the tank, it can't effectively take away all the heat produced from pump and engine, and from outside temperatures (this helps cool electronic portion of pump also acting like a heat sink) in hot temps.

Adding a lubricity additive takes care of the mechanical portion of fuel pump, as does keeping fuel tank near 1/2 full or so at all times, for proper fuel system cooling. As with most diesels, they only burn a portion of what is actually pumped through fuel system, most is returned to tank for cooling/lubricating/aerating.

In all my years as a Diesel mechanic, I have never seen rotary pumps on any type of light or heavy equipment, last as long as an inline oil lubed pump, nor are rotary pumps as reliable IMO. Couple that with low sulphur fuel, and a fueling box going over the design parameters of rotary pump stroke length, can or may equal disaster.

Rebuilt/reman pumps if not checked over properly when repaired can cause early failures also, especially if they don't have a QC program in place. Then there is the unexplained "luck factor" also that can't always be explained. All we can do as owners is to be aware of things, follow good maintenance procedures, so that we can minimize their eventual failures, and hopefully have a "little luck" along the way. That being said I have 225,000+kms on my original VP44, and going for a new record.