How much fuel pressure is too much?

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skav

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I had a problem w my FASS 180, so I ordered a replacement pump. I installed it today and primed the system.

Once the truck fired, I noticed that my 30psi fuel pressure gauge is now pegged. Before the replacement pump, I had 25psi at idle and around 21 when I was on it.

Is this too much pressure for a II hot rod 44?
It starts fine and idles, but I haven't driven it yet.


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Ive always been told, no matter whats done to the vp44 keep fuel pressure around 15psi. i run mine at 25psi becaues i loose 10psi at WOTso it drops me to the sweet spot.
 
Not to steal your thread but I was gonna ask a similar question, I have an airdog 150 that I had on my p-pumped 24 valve that stayed around 26-28 psi, I was going to put it on my vp truck, but is that a bit too much for my so vp44, what do you guys think is the limit?
 
vpdually said:
Not to steal your thread but I was gonna ask a similar question, I have an airdog 150 that I had on my p-pumped 24 valve that stayed around 26-28 psi, I was going to put it on my vp truck, but is that a bit too much for my so vp44, what do you guys think is the limit?
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No worries. Hope we both get our questions answered.

I ran 25psi forever without any issue. I'm just not sure what point is too much pressure.

I was told be a shop that a lot of guys run 50psi. Idk, but tomorrow when FASS opens, I'll give them a call.

There is supposedly a screw that you can adjust to reduce the pressure, but I don't know where to find it.


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I just called Brown's diesel and they are saying 18-20. Now I need to figure out how to adjust the pump.


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I wouldnt go over 25#and 20# is plenty. You should be able to order a lighter spring for the return. If not you could plum in a regulator.$.02
 
As stated 20 psi is plenty for a VP truck, anymore than that and you risk doing damage to the internal diaphragm of the VP. If 20 psi at idle can't support your flow needs at WOT you need to upgrade lift pumps.
 
I put an Air Dog 150 on my truck. Came out of the box set at 20 psi. The truck is just my screw around pulling truck for now, so one day I got the bright idea to turn up the fuel pressure. While the truck was running I turned the pressure up to 30 psi. I went to get fuel, shut the truck off, fueled up and it wouldn't start. Anything over 20 pounds in my truck and it doesn't have a prayer at starting.
 
I was always told no more than 19 psi at idle on a VP44, and anything more can damage the internals
 
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I run my raptor 150 at 20psi and wot it still drops to 5psi. Going to add a second raptor as a helper. 20psi is what I have ran on all my vp trucks and never had an issue

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Pressure is a measurement of restriction, that's it. Pressure isnt necessarily what you want, FLOW is what you want. High performance engines require alot of flow, pressure drop is a result of not enough flow.


...and a second raptor will give you just that: more flow.
 
I just replaced the return valve and that helped thing out also. The old valve was really soft compared to the new valve.

It sits at 22-23psi now.

Here's a quick question about the plumbing.

I noticed that everything was plumbed in -8, and confirmed w FASS that this is correct. It seems small to me. On my 7.3, I ran a -12 pick up from the tank to the FASS, then -10 to a Y. From the Y, I ran -8 to the heads.

Is there any advantage to running -12 to the FASS and -10 to the IP?

Also, has anyone removed the return valve and installed a fuel pressure regulator? Would this make any difference?


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Guys, all the VP44 needs is 15-18. and it needs to stay above 5-8 at full throttle/rpm.

ANYTHING above that is just heating fuel by pressure and is detrimental.
This pump isn't like the mechanical pumps.

The VP will only pass so much as a cooling fuel.
you should be much more concerned with coolling air flow to the pump to reduce heat soak.
 
man, my pieced together setup never drops more than 2psi from idle to level 9 pm comp wot in od.
throughthe factory filter housing.. Gutted and ported of course. Automotive pump to Holley regulator. -8 all the way, with an fittings on filter and pump. Works like a champ! Btw 17 at idle 15 at wot
 
BTW, I replaced the fuel return valve yesterday, and it's not smoking as much off idle.

It's set at 22-23psi, and drops to 20-21 under load.

I just received the new reg spring and ball from FASS, which is supposed to hold the pressure between 15-18psi. I haven't had a change to try it yet.


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