Cummins 24v losing power under load, randomly

[slaymaker3]

Lift pump

[jackelope]

My unofficial over the internet, non-strategy based diagnosis/guess is that the lift pump failed causing the injection pump to overwork itself and burn out.

[JohnVH]

Does it have a fuel pressure guage to keep an eye on the lift pump? Thats the first thing I added when I had my old '99 24V, then I put a Airdog Raptor FRRP in place of the factory lift pump.. 

Hope you get it figure out, intermitten issues are frustrating!

[Bigtine96]

My unofficial over the internet, non-strategy based diagnosis/guess is that the lift pump failed causing the injection pump to overwork itself and burn out.

yep, I literally just had this problem a month ago. But I have full pillar gauges so I was able to see that my fuel pressure was at 0. It started bucking under acceleration just like the op, Threw on a new FASS 150 and the world is right once again.

OP do not continue to run your truck if your not sure your getting fuel pressure you will burn up your $1000 VP44. And normally when the VP goes it just goes and you get a death code and you cant start the truck. Don't let a shop just throw a new injection pump on.

[deadwoodbuck]

timely thread...so what is this VP44?  I have a newer high performance FASS lift pump when the injector pump just quit...so did the truck.  replaced the injector pump...greased up first...$1000's later.  it was a rebuilt pump.  now it starts first time but after running...especially on hot days...it just turns over and over and over till I get pissed stop and try it again where upon it starts up...no codes or check engine lights appear.  is it the rebuilt injector pump or this VP44 thing?  2000 2500 24v  also just realized that I need an updated computer flash drive for the truck computer...something about a long ago factory recall?  my tranny upshifts and downshifts frequently

[Bigtine96]

timely thread...so what is this VP44?  I have a newer high performance FASS lift pump when the injector pump just quit...so did the truck.  replaced the injector pump...greased up first...$1000's later.  it was a rebuilt pump.  now it starts first time but after running...especially on hot days...it just turns over and over and over till I get pissed stop and try it again where upon it starts up...no codes or check engine lights appear.  is it the rebuilt injector pump or this VP44 thing?  2000 2500 24v  also just realized that I need an updated computer flash drive for the truck computer...something about a long ago factory recall?  my tranny upshifts and downshifts frequently

Your lift pump supplies fuel to your injection pump "VP44" and the injection pump supplies your fuel through the fuel rails to your injectors. When you get hard hot starts like your describing its because the computer on the top of the vp44 is shot from being exposed to heat. The only option is to buy a remanufactured vp44 again, it is a good idea to buy from a well known vp44 rebuilder because a lot of companies will just rebuild the internals and not replace the computer which is what im assuming happened to you unless the vp that you have has been on your truck a while. Your fuel pressure to the vp44 should always be above 10 psi at full throttle and generally around 17-18 psi at idle. This will give you the maximum life for the vp and since you have a FASS you should be running about that pressure.

[deadwoodbuck]

so Bigtine96 the guts were probably replaced on the injector pump, VP44, but the computer on top of the VP44 probably was not replaced and or upgraded accounting for the hard hot starts?  you make much sense to me and really appreciate the new insight.  I did have the work done by a reputable shop and assumed that that whole injector pump VP44 including the controlling computer would have been replaced.  the vp has less than a hundred miles on it so they should replace it for me.  it seems like you are saying the vp/computer are one big package.  thanks Bigtine96 for this good info

[Bigtine96]

so Bigtine96 the guts were probably replaced on the injector pump, VP44, but the computer on top of the VP44 probably was not replaced and or upgraded accounting for the hard hot starts?  you make much sense to me and really appreciate the new insight.  I did have the work done by a reputable shop and assumed that that whole injector pump VP44 including the controlling computer would have been replaced.  the vp has less than a hundred miles on it so they should replace it for me.  it seems like you are saying the vp/computer are one big package.  thanks Bigtine96 for this good info

Glad I can help, Yes the vp and the computer are in one package, if your having hard starts after only 100 miles there is definitely something wrong. 99 times out of 100 hard hot starts are attributed to the computer failing from heat, just a crappy design, you should have a warranty with the VP. When your talking to the shop get the name of the company that supplied the injection pump and see if they do replace the computer when they rebuild their pumps. 

[deadwoodbuck]

thanks much...I did run that by the shop and they said it might be high fuel pressure not allowing the pintle valve in the vp to open up due to low voltage at the time the engine is cranking.  in other words, the FASS after market pump is creating to much fuel pressure on that pintle valve (think fuel solenoid) for it to open up at low cranking voltage.  crazy stuff...oh also could be a ruptured diaphragm in the vp...which they would replace.  thanks for giving me something to think about.

[Bigtine96]

thanks much...I did run that by the shop and they said it might be high fuel pressure not allowing the pintle valve in the vp to open up due to low voltage at the time the engine is cranking.  in other words, the FASS after market pump is creating to much fuel pressure on that pintle valve (think fuel solenoid) for it to open up at low cranking voltage.  crazy stuff...oh also could be a ruptured diaphragm in the vp...which they would replace.  thanks for giving me something to think about.

No problem, a good investment would be to get some gauges so you can see your own fuel pressure. But if the FASS hasn't been tampered with as far as the fuel pressure spring you shouldn't have to high of pressure and that wouldn't affect you for only hard starts. you would be getting hard starts no matter what temp the engine was at. I know a lot of guys that are running over 20 psi with their systems and truck runs great. But now you have a direction to look goodluck

[gonehuntin68]

VP44 going out. Checks out fine because it's not all the way gone yet. So it reads good when being checked.

[Wanttohuntmore]

Update, the third MPS seems to be working.   Though, it didn't help me get a nice 5x5 on Saturday

Going back up again to close the season out.  Dad is running pressure gauge lights but not gauges.  He's getting full gauges next, a new transmission, and should be good for at least another 150k.

[kirkl]

What is the MPS again?

Speaking of fuel additive, what does everybody run? I use stanadyne in my 03 dodge every other tank or every third tank. My injectors went out under warranty at 100k so making sure I dont do that again. never really ran additive before that.

[deadwoodbuck]

I finally had had it with all my 2000 2500 diesel problems.  an auto computer and electronic expert said that this year dodge had many many electrical problems...bad grounds, wires running to close to alternators and other areas.  he said the dealers knew about this but did nothing to fix the problem.  so after re-flashing the computer ( another factory necessity), re-routing many wires and re-doing many grounds...all my problems seem to be over.  ultimately the speed sensor was the final straw emiting so much noise that it was causing problems for the computer.  the set points for the tranny shift changed, cruise control works, AC works and the hard hot starts have disappeared.  bottom line those year rides have many electrical problems that it might very well be your problem.  it sure as hell worked for me.

[Slimdog350]

I guess it depends on your definition of low power is. Is there any response at all or does it feel like a dead pedal? I've had two co workers trucks I fixed recently and they both had the same issue. It was the throttle position sensor had a dead spot in it causing a "low power" feel to it. One is a 2001 dodge and the other is an 03. Dodges are notorious for crapping out lift pumps and the vp44 pump was a joke. Dodge had an update to install a pump in the fuel tank to replace the lift pump. Hope you get it figured out and back in the woods!