Well this problem has been going back and forth for months now. I have a raptor 100gph pump with a 6 month old vp. For about 2 months now the truck has been starting up well. A few days back now it starts up awsome when cold or when i let it sit for about 3 hours. But if i run it and turn it off and hop in it about 10-20 mins later, it takes awhile for it to start almost like its loosing prime, or the fuel is draining back? Im not sure im lost on this one, im purchasing a larger air dog tommorow 150gph, because my raptor 100 cant support the fuel that i need, bacause my fp gague will bounce when i demand heavy fueling.

 

I think you need a different spring on the pump. A 95gph fass supplied me with 603hp. as for the warm starting issue only thing I can think is your raptor running when your cranking if so vp's do not like to start with excess fuel pressure.

 

Exactly what he said. Too much pressure on initial start will cause a hard start.

 

I can hear the raptor cycle when i first turn the key on, then it goes away... it just started happending again. it went away for many months then started doing this! and were can i get a bigger spring for my vp

 

for the raptor not the vp

 

I really hope it is a lift pump issue, but I do want to put this out there. Hard/long starts when hot is a symptom of a cracked diaphragm in the VP44. It may be the Injection pump, but I hope not for your sake.

 

I just replaced my raptor 100 with a air dog 150 all quick connects got rid of the old fuel lines ran the hose from the air dog right to the vp, still have the same problem.. The problem went away while it was cold here in ct, but now since its starting to get hot out again it just started with the same problem and acually getting worse. Im gonna try to see if the vp is under warrenty but i taped into it with my quadzilla so prly not

 

Hard starts when hot are usually signs the VP is going out.

Luke

 

Looks like its time to save for another one

 

Have you taken it to a good diesel shop to have them diagnose this issue?