Vp44 swap, now intermittent hard start...ideas?

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0767cummins

I remember my first hx35!
Joined
Aug 16, 2010
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I had a vp44 from a 99 auto with 250k on it. I put that pump on an 01 6 speed with 120k on it. Now whenever the 01 is up to operating temp and I shut it off it starts hard. If I let it cool down it fires right up. Would there be an issue with the 01 that originally came with the HO pump since I put a none HO pump on it ? I haven't found any fuel leaks so it's not losing it's prime... I can let it set for days and it will start right up. But once it warms up it cranks and cranks before it finally fires .... Any ideas. I don't wanna throw a reman pump on this truck just to find out I still have the same problem...
 
Check your fuel pressure, should be real close to 15 psi. Much more than that can put too much fuel pressure on the diaphram in the VP pump and cause it to hard start warm. I've got a 99 and an 01 here doing the same damn thing! My fuel pressure on the 01 is 22 psi, lower it to 14 and the problem goes away. Also, hard warm starts is also a sign of a bad injection pump. Hope this help's, Gary
 
I did adjust the fuel pressure a while back to see if that cured the issue. It was at 23 psi. Dropped it to 18 and it seemed to help. I'll try to drop it to 14 soon to see if that cures it.
 
i did a lot of reading on this topic because i had a SO truck with a HO pump on it. It ran fine. From what i read and what ive heard you can put a HO on a SO but not vice versa. That being said nobody could ever tell me why so id still go for basics, fuel pressure and possible air intrusion, after that prolly a bad pump
 
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