2000 Cummins.

This thing can sit for days. Jump in turn the key and it fires, just like it always does.

If I drive it for 30-45 minutes turn it off and say run into the grocery store it's a real SOB to get it started again.

I'm running a second lift pump back on the frame rail and I've had hard start problems in the past once in a while that I attributed to higher pressures into the VP44, but nothing as bad or as consistent as this.

I can't find anything that would indicate a leak of any kind, but it sure acts like it's got air in the fuel system. I've noticed that when I have these hard start problems I can hear the lift pumps running for quite a lot longer than I am used to with a warm truck, almost like it's pushing some air out of the lines.

I'm thinking that the my next step should be to replace the check valve on the input to the VP44.

Anyone got any other suggestions?

 

what kinna fuel pressure are ya hittin the VP with??

You say ya run a second lift pump so I am assuming yer doin more than 14psi

The VP dpnt like more than that and some times it makes em hard to start

 

Yup I'm running more like 15psi at idle, and I have had an occasional hard start since I added the second lift pump, but generally only in the summer and never as often as it is currently happening.

That was my initial thought, but what bothers me about this theory is why does it not happen when the truck sits for a while?

That's how I came to suspect the check valve. If it's sticking closed and slowing bleeding pressure off of the VP44's input that would explain why it starts fine after sitting a while.

 

I am no expert by any means but I believe the diesel sets inside the VP and the heat causes more pressure which inturn causes the hard starts


I have said it a few times on here before but I think the 2 pump system is a bad thing to do, 2x as many things to do wrong

go with one good proven after market pump and do it up right

 

True enough, but at the time (7 years ago) there weren't a whole lot of other options. It's been working good up until now. So I'm trying to figure out what's changed.

 

The dual pumps work great if you run them side by side but not through each other. Almost all LP out there have an internal bypass and as long as they run parrelel to each other you will never go over the max that they are set at. So if they are set at 15psi no matter what even with two pumps pushin you will never send more then 15psi to the VP. Myself, I ran dual pumps for some years but had a switch hooked up so that I could run either one of them by itslef or for tmes of heavy pulling when I needed the extra fuel I could turn them both on.

I would suspect that your problem is the VP going bad and this is the typical hot start problem with it. The first time each day you start the truck it fires right up but after that if you shut it off it has to sit for hours for the pump to completely cool off before it will start again.

 

Well I changed the check valve out on Weds night.

Didn't run the truck at all yesterday (snowmobile ride for work). Ran it today and the hard start is gone. Lift pumps run like I'm used to them running, and the truck seems to be running a wee bit smoother.

Bottom line before dropping 2 large and half a days work on a new VP44 spend 23 bucks on the check valve.

 

I'm having the same problem....where did you get the check valve replacement? Easy to replace? I'm assuming this was on the intake banjo fitting?

 

Hes talking about the overflow valve on the VP-44. It very likely came from Cummins or a diesel injection shop. Will be dead easy to replace (make sure you get extra sealing washers).