Did a Ford cummins conversion and installed a Fass system. When the weather was warm the pressure never dropped off of 18 psi under any load, now that its getting really cold for some reason my fuel pressure at idle is 18 psi. But if I start going under heavy throttle the pressure drops to 4 psi but no lower (the truck is at operating temps while testing.) Is this low pressure safe for the VP44 to operate or is it gonna grenade? I would rather fix this problem then get a new inj pump. Is it a problem or am I OK. Thanks!

 

No lower then 10 psi on the VP44.Might want to check the filter and water seperator.What size line is going to the VP44?

 

ive got 3/8 lines in and out. Its wierd cause it was fine when the outdoor temps were higher. but now that its 20-40 degrees all the time the pressure has gone down. No leaks of any kind and I changed the fuel filter just in case. Also checked for line damage (kinks and such). Perhaps my new fass pump is going out? Is running the pressure lower than 10 psi gonna damage the VP44? I dont really notice a loss in power or any noise differences from the engine. The gauge is mechanical taking pressure just before the fuel filter assembly.

 

Try bleeding the gauge there may be some air in it.

In time running it below 5psi will damage it,10psi seems to be the the stop spot for aftermarket pumps FASS,Airdog,ect.With good pressure means good cooling for the VP44.The only other thing is the pressure regulator which is in the FASS pump.

 

anything 4 lb or lower its just a matter of time.

 

I run a fairly constant 22 PSI, seems to be holding well.

 

Is there such thing as to much pressure on a stock vp44? In other words would a FASS 150 be to much?

 

Yes - the point at which its too much is debatable. Most guys dont like running much over 20 psi.

the FASS 150 is just fine. It should come with a regulator which allows you to turn down the pressure.

 

Mine doesn't have a regulator on it, at least not one that can be adjusted. Mine is about a year old, and is the Heavy Duty series, maybe the new ones are different.

 

I've been running at 18-22 for 90K miles/eight years without a problem.

I had the symptoms the OP's described - although not in a FASS pump. Turned out there was an ice-plug at the pre-pump filter - a wad of gunk around which ice had formed. Just a thought.