rockwithjason

my vp44 gave up the ghost. i can't really be to mad at it as it has 100,000 on it since i bought it and possibly 180,000 if i count the previous owners mileage. i was on the road with no time or facilities to do the repair myself so off to the cummins shop it went. the truck was running 75 down the interstate when it went to a rough running 900 rpm and had no power. the obvious stuff like a lift pump and bleeding the injectors was tried as a roadside repair but to no avail.

looking back on it, it seems that the truck was only running on 3 cylinders. the cummins tech diagnosed the vp44 failure. no codes were present so the internal mechanicals failed. the tech stated that the root cause was low voltage due to me only running one battery. in order to preserve the warranty on the new pump i would have to go back to the dual battery set up. i explained that i live in a hot climate and never really needed the cold weather starting power. the tech explained that the weather was irrelevant. the electrical system needs the reserve capacity of two batteries to ensure that the voltage never dips too low to the vp44 causing failure. now to be honest i don't know how much stock to put in this but i am following his advise and calling it cheap insurance.

for the new guys here are some links to vp44 diagnosis information. if you search you may find it already posted.

http://www.bluechipdiesel.com/vp44_diagnostics.html
http://abdiesels.com/forum/index.php?showtopic=3091

mrclean

[QUOTE=rockwithjason;3149170]my vp44 gave up the ghost. the cummins tech diagnosed the vp44 failure.
the tech stated that the root cause was low voltage due to me only running one battery. the electrical system needs the reserve capacity of two batteries to ensure that the voltage never dips too low to the vp44 causing failure.[QUOTE]

I wouldn't put much stock in that statement. I'd say he just doesn't know what he's talking about. Much more likely it was just that pump's time to expire.

KATOOM

180,000 is great for a VP thats potentially spent a good portion of its service with fuel pressure too low. Especially if you live where the ambient temps are warmer.

As for the diagnosis, I'm not sure I agree since first off you wouldn't have been able to tell if it was running on only three cylinders when the engine is off. And if it was running on only three then yes power would be terribly low but the vibration would have been immense. Also, no codes most of the time means an electrical issue in the VP computer since mechanical issues are what throws indicating codes. And needing both batteries isn't necessary unless that stand alone battery is weak and isn't able to provide the full 12 volts. The VP pintle valve needs 9 volts to function but there's nothing I've ever heard of which states that low voltage is damaging to the VP. The main reason for two batteries is to maintain optimal amperage during engine starting in cold and hot weather. No matter, its running.