Left for a vacation in Colorado last weekend. On the way out there, I noticed the truck seemed to be using more fuel than normal. As I was climbing up to Estes Park out of Boulder, the truck seems way down on power then I start getting the intermittent "dead pedal". Once at the cabin in Estes Park, I cycle the key to check for codes (never got an MIL) and I just about puked as they read off--- P01693 (DTC in companion module) P0234 (overboost) and P0216 (IP timing failure).

Strange thing is, fuel pressure was fine according to my in cab fuel gauge... never gave any indication an impending problem. Got up the next morning and made an appointment at Cummins Rocky Mountain in Henderson, CO to get the truck checked out. The following day, we shuttled the truck over to Henderson and $220 and 2 hrs. of diagnostics later, it was confirmed..... almost dead VP44 (P0216 code was logged 58 times), lift pump becoming borderline - still working but getting very noisy.

Also diagnosed was a weak bypass valve. This $10 part appears to be what took out both the lift pump and the injection pump. The bypass valve was either hung open or popping off way too early allowing too much fuel to return to the tank and starving the IP of fuel. This was working the lift pump to death as it was basically running full bore all the time with little to no restriction.... it just wore itself out. Like I said, it was still working and supplying plenty of fuel to the VP44, the bypass valve was just returning most of it to the tank. The lift pump sounded like it was full of rocks.... very noisy.

So, just because you have a fuel pressure gauge (like I do), that doesn't mean you are ensured of catching a problem before losing a VP44. I talked with the Tech that worked on my truck out in the parking lot and he showed me where the bypass valve is located. He also suggested removing the bypass valve and thoroughly cleaning it every other time the fuel filter is replaced. With a repair bill of almost $3600 for a new VP44, new lift pump and the labor to install them, you can bet I'll be keeping a close eye on this little $10 menance to bank account.

 

Where is the bypass valve located? I have never cleaned mine.

 

If your overflow valve was weak, why did you not see the fuel pressure drop on your in cab pressure gauge? Maybe there is more going on inside the VP44 than most people realize.

I don’t mean to make waves and getting a VP44 replaced to restore power and mileage seems to be all too common, but I am having trouble believing the spillback valve has any lift pump connection.

 

That checkvalve has a 1/8" hole in it with a bb in it with a spring behind it. It can't let that much fuel though. (your pump will pump a 1/2 line full), If you had pressure in the cab, then it wasn't what caused your vp or lp to fail. IMO. It failed because it's a bad set up all together. If you have a vp, you will someday have to buy a new one, no mater how much pressure or volume running to it. JMO

 

Yea if yall could point out to me where exactly that thing is i'd appreciate it, like Coachgrowl i aint ever cleaned it and would like to make that part of the maintenance chores

 

Sorry for the delay.... had to wait for the photo to be approved before I could post it.



It's #4 in the pic.... the FMS calls it an overflow valve.

 

After you get it cleaned, let us know if you think you done any good.

 

It's not a performance enhancement type of thing.... it's more like a maintenance thing to ensure that it is working properly. If the valve is hung open, it can result in decreased engine power and damage to the VP44. If the valve is stuck shut, it can result in a hydro-locked VP44, hard starting, increased fuel temperature and damage to the VP44. The tech just mentioned it as a good idea to check regularly to make sure it's working properly since damage to the VP44 can result, either way, it it's not functioning properly.

 

Have you looked at this valve? not much to clean. It has filter diesel fuel running though it. Not much better solvet to use than that.

 

A reputable rebuild shop will include a new overflow valve with the reman pump. Every pump that I have put on, has a new valve with it when it arrives.

Just like using the key that comes with the pump, use the valve that comes with it, and if it doesn't come with one, make sure to ask why not.

 

Yes, I have. If you're not [ooops... left out the "not" first time around] careful when doing filter changes, you can let some unfiltered diesel pass through to the IP. It's not a matter of it getting gunked up, it's a matter of a piece of debris, etc. lodging in the valve keeping it from fully seating or fully opening. I'm just passing on a tip from a tech that works on these things all the time and has said that he finds debris in quite a number of them. It's just another "ounce of prevention" that one can do when maintenancing their vehicle. Busting my ***** about it isn't going to change that fact, so either check/clean the valve if you want to or don't if you don't want to. I'm just sharing some info that was given to me.....

 

I'm just saying that this check valve is after the fuel has passed though the vp, so it can't bypass the pump and go back to the tank with out going though the pump first. It is always open when the truck is running. If you were having problems with your truck loosing prime, then yes it could be stuck open, but it won't take out your vp. And yes all 6 pumps I've put on in the last year and ahalf had a new one with it. and I did use the new ones. But all the old ones looked just fine. I'm not bustin your *****. Just because some tech said it don't make it true. Just as me saying it don't make it false. So you clean your as often as you want. All I wanted was someone to tell me afterwards that they though they did some good. So take my advice for what you payed for it.

 

I know this happens but I can't understand how. I had this happen with a GM diesel. Every time they would change the fuel filter, I'd get one or more clogged injectors. Every time. Same thing with my furnace. These guys even know to come back about 2 hours after they service the furnace and change the filters on the oil tanks. I've seen them do it. Shut the fuel off before the filters, remove old filters, drain some more fuel out of the lines with no filters, install new filters, bleed the system, runs OK when they test it, jets clogged within a half hour. Take the jets out and black debris. I just don't understand how that gets through the new filters.

 

....also note the small orfice fuel travels through where the check valve screws into....