how much fuel pressure are you supposed to have going to the vp44?

 

Anything over 8-9 PSI at WOT is acceptable, most folks go with aftermarket pumps that will raise WOT pressures to ~15psi.
Over 20psi will give you hard start problems.

 

and potentially cause your fuel filter canister to leak. Many have been down this road.

 

yep, your goal is keepin it between 10-20.

 

Never EVER below 10 psi is the critical number you really need to care about.....but the high limit is heavily debated by some. What I mean by that is, there is ZERO proof anywhere indicating that high fuel pressure pressure is bad for the VP. If someone doesn't believe that then please, show me otherwise. With that said, I will say that anything over 20 psi is unnecessary and just means that fuel in the tank will be cycling through the fuel return more often. Thats not a problem in the winter but in the summer heat, as your fuel level drops you're only going to cause the fuel tank temperature to increase as fuel passes through the VP, engine, and fuel module basket over and over and over. In the summer, I try to keep my fuel tank level at no less than 1/3 full, unless I'm on a long road trip between stations. The volume helps offset any heat build up so the VP is less likely to see hot fuel.

Now, the reason they say high fuel pressure causes hard starts is because the VP's pintle valve can possibly stick as a new aftermarket high volume/pressure fuel pump can place to much pressure on the VP during engine cranking. Although running high pressure while driving has nothing to do with hard starts. Its all about the cranking pressure. This can even be an issue with a overly productive OEM lift pump too, but is rare and mostly common with aftermarket fuel pumps. The way to deal with a hard start issue caused by fuel pressure during cranking, you can either have someone with a Smarty flash the ECM to stop the fuel pump while cranking, have a dealer do the same thing for money, or install a $5 relay in the fuel pumps wiring. This only if you are having hard starts for that reason.

So if you're asking about what's the "right" fuel pressure.....I have my fuel pressures set up at 19 idle and 16 WOT. After years of reading and researching, I have come to the obvious conclusion that I needed to set my fuel pressure that way because 1) OEM fuel pressure specs are already at 15 idle and 10 WOT, 2) the VP's overflow valve is factory set from Bosch at 14-16 psi, 3) the VP is ONLY cooled by fuel so for that reason fuel must pass by the VP at ALL TIMES to keep it cool, and 4) with my settings fuel is always passing through the VP, 5) this somewhat new approach is now heavily considered by many aftermarket companies where before it was considered that as long as you had 10 psi, you were good.

 

Mines been at 20-22psi for years now, no issues, starts good.

 

I run an aftermarket FASS at 12-16 PSI. It fluctuates based on air temperature, and fuel additives.

 

12 at idle, 6 under the hardest of loads. Volume over psi ANY day!

 

22 at idle and 16 at wot, no hard start problems

 

I have run my fuel pressure at a constant 7 PSI for the last 10 years. I guess I am just lucky or I don't buy into to fuel pressure myth. I lost one VP44 for electrical problems but am not worried about the replacement pump with the better electronics. To each his own.

 

I was waiting for this..... Yes, you're right and in truth, no one can really answer the quagmire of the VP. If you haven't seen the this thread http://www.cumminsforum.com/forum/98...ng-00-ctd.html then you'll read that the truck has 1.7 million (yes million) miles on the engine.....still on the original VP. He went through some lift pumps but the fact the the VP is still OEM is unheard of. So in point, the main things we currently understand about the VP is that heat is its enemy, and unlike the oil cooled P-pump, fuel is the only thing that cools the VP. Keep fuel flowing through it while driving and it stays cool but shutting the engine off is a problem because then the engine heat soaks the VP which causes the computer to get hot as no fuel is passing through the VP anymore. Thats an issue no ones been able to solve yet. Also......the temperature of the VP depends on where you live and how you drive as well. If the truck runs more than its shut down then the VP will be happier. Live in a cold climate and the VP will be happier. If the trucks an around town short hopper then the VP will suffer from the constant start/stops. If you live in an area where the temperatures tend to stay warmer then the VP will run hotter. You obviously live where warm summer weather is cherished so maybe that has something to do with the fact that your VP's computer is lasting with such low fuel pressures. Cant say, but I can say that the VP's computers are NOT an upgraded item. Bosch unfortunately still uses lead free solder and they still suck. The only thing that helps the computer last at all is the cooler running VP from other mechanical upgrades.....and better fuel pump systems.