Hello,
I've been struggling for the past few days. I was getting low pressure to my VP44 (11psi@idle, 5psi@WOT) so I replaced the lift pump. After that, the pressure fluctuated less, but the pressure was still low (10psi@idle). When I did the swap I eliminated most of the banjo bolts, so I'm pretty sure the problem doesn't reside with supply line restriction. I figured the problem might be with the Bosch Overflow Valve on the return side of the VP44. I've been looking into ways of modifying the stock valve (first pic attached), but the ball bearing that is retaining the spring assembly is too hard for me to drill through with the machining tools I have access to. I would have to roll the dice and buy a $50 carbide bit that *might* do the job. Unfortunately, no EDM machine in this shop. I also looked into just buying a fuel pressure regulator for the return line and eliminating the overflow valve, but diesel rated fpr's are two hundo at the cheapest for 15-20 psi adjustable capability.

So, this leaves me with my main question. Can I put one of the 12v overflow valves on (the ones that come apart) and modify the spring for my pressures? Or while I'm at it, would I be able to install the Tork Tek adjustable valves for the P7100 pump on my VP44 (http://www.torkteknology.com/product...-OFV020.html)? I've read that the VP44 is rated for 15-20psi, and it looks like that Tork Tek is set to 30psi but is adjustable. Has anyone tried to turn one down to 20psi? Are the threads/sizing the same between the two injector pumps? Any info is greatly appreciated. I've been searching for an answer for the better part of a week now.

 

You don't say what type of lift pump you have. If you have a stock lift pump, your pressure is about normal. Read RAWilliams article on the overflow valve. I think I would lean more toward a larger pump system. I have a Wicked Diesel Eliminator pump system on my 2002 (that pump is not made anymore), I hold 16PSI with no fluctuation. I have an Aeromotive #13301 regulator, and they claim it is OK with diesel.

 

Here is a link to a test procedure:

https://www.dieselbombers.com/98-5-0...formation.html


I have thought of an adjustable overflow valve as well, but to reduce my pressure.

 

I'm running the Carter HP4601 installed in the factory location. Planning on upgrading to custom filter system, bigger lines, and an improved draw straw in a month or so.

Those are normal pressures?? Pretty sure everywhere else I've heard the VP44 needs atleast 10psi at all times. I think the factory spec is 15-20. That's just what I've read though.

That regulator looks like it's a pretty reasonable price. How did you mount it? It has 1 inlet, 3 outlets, and a return, correct? Did you just plug two of the outlets and the return, then connect the remaining outlet port to the factory return line? Thanks for the input.

Anybody else have any input on the whole putting P1700 Overflow Valves on VP44's?

 

My factory service manual calls for min 10PSI. Before I went with the current system, I had my stock lift pump mounted back near the tank, with all 3/8 lines. It used to show 12-13 PSI. I got tired of replacing stock pumps. On the Aeromotive regulator, I plugged two of the holes, and ran a 1/2" return line to the tank fill tube. Eventually, I hope to go to a draw straw, and have the return into the basket.

I'm not that savvy on the inner workings of a VP44. You might give Chip at Blue Chip Diesel a call and see if he thinks changes to the overflow valve would be advantageous or not.

 

Sweet, will do. Thanks!