Hi all, I'm new here but am on the 'other' site also. Over the last week I've been chasing a hard start problem. Fuel pressure reads 13 @ idle and 9 @ WOT. No white smoke, no codes, good power, runs great. 3 days after the hard start started I threw my first code of a P0336 - CPS. So I changed it. Cured the code but did not fix the problem. In doing research I discovered the check valve issue. I pulled mine today and can VERY easily push down the check ball with a thin allen wrench and noticed that before I pulled it, my LP prime before actual start would immediatly drop to 0 (but it did this when it ran fine, too).

When I reinstalled the check valve, I did notice that when I went to start the enging, the LP primed @ 13 like normal BUT bled off very slowly. It did that for the first couple tires then the prime pressure dropped like a rock again to 0.

I don't think I have a bad VP (praying) but can this little check valve be the source of my hard starts? If it's running and I shut it off and immediately restart it, it will fire.

My new valve will be here tomorrow but I find it strange that I can barely touch that little ball and lift it off the seat.

PS - new lift pump going in tomorrow also (Fass HPFP).

Thanks very much for your time.

Mike.

 

Your bein smarter then the average bear here. That little valve can very well do that and causes many folks to change the pump when there is nothing wrong with it at all. If it is stuck open or closed or the spring is just to weak to hold the pressure it can cause all kinds of issues.

 

Uncle Bubba - thank you very much. I hope that is the problem.

Based on the info and 'lack' of VP44 issues that I don't have, would you lean towards the valve?

How's this for a test? Have a buddy in the truck, turn the key to 'run' while I'm under the hood pinching the return line closed. Then see if it will immediately fire.

???

Thanks again, Mike.

 

let us no when you change it how much is a new valve definatly something to check before shelling out some major dough

 

Deffinetely worth checkin first. It's also a good thing to change this if you install a new pump also. If your having fuel problems associated with starting or running right chack your fuel pressure first both at idle and WOT and this valve next.

 

I'm pretty sure I did that already - I have my FP guage adapter mounted on the supply side of the OEM filter canister to the VP44, not the inlet from the tank. Idle pressure is 12-13psi, WOT on the freeway is 9 min.

Again, no white smoke etc.

 

I'm not giving any expert advice here by all means, just that of a guy that has personally fought every fueling issues these Cummins have ever been known to have and a few extras.

Pinching off the line may work as long as you pinch it off just before you shut down the truck to make sure that the line is full of fuel. Otherwise your prime will just be fulling the return line if it's opening to soon. The other issue here would be if you were to overpressure the the VP44 internally, I don't know enough to know what that could do.

If you have this valve out what I found is that 4 pounds of pressure should open the valve. If you have a scale of some sorts, in my case I used a hanging scale and made a hook that went inside the valve to push on the ball and the other hung over the scale. I don't know any science behind this. A good check valve is supposed to maintain a pressure of 14psi. I made a tester by welding a couple of nuts together and using an air pressure fitting in one side and screwing the banjo bolt in the other and set the compressor at 14psi and tested it this way. One that tested out like this took 4 pounds of pressure to open it.

Sorry for the long explanation here but I know some sience minded guy was gonna come along with a bunch of formulas and tell me this was wrong and i was just beatin them to the punch. I'm a tinkerer not a scientist.

 

There's some great info on this subject in this thread if you want to do some reading.

https://www.dieselbombers.com/24-val...el-system.html

 

Ha! I hear you, me too.

Thanks for the link, I saw that one yesterday. The way I 'tested' my valve was to just lay it on my bench with the ball/hole facing up. I inserted a thin hex wrench into the hole 'till it touched the ball and then barely pressed and I could lift the ball off the seat with hardly any pressure. I would say MAYBE 1 psi. Hell, I think I could balance my cell phone on the hex key and still unseat the ball a little.

PS - Ole Red - the valve was 38 bucks @ my local dealer.

 

I did the one write up in that post after my truck had been sittin dead for over a month cause nobody could figure out what was wrong with it. Me and the kid ended up stripping the fuel system out of truck completely. I mean if it touched fuel it came out, then started puttin it back together one piece at a time and that's where I learned some of that stuff from.