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Fuel Boss lift pump?

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I have had it on my truck now for about 3.5 months now it was at 15psi idle and 22 wot now my idle psi has dropped to 12 but wot is still the same.Will a dirty filter cause this I have not checked it yet but will tomorrow.I changed the filter when I installed the pump I would say that I have about 4000 miles on it.What else would cause this. THANKS

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fuel temp change will do this, when its real hot ill see it drop to 13ish and fluctuate but pick right back up under throttle.

  • Owner

Usually the fuel pressure on the WOT will drop with a dirty filter where demand is the highest.But if the coolant temperature is high your idle could drop lower causing a drop in fuel pressure.

  • Author

Yea I believe the Texas heat may be the problem I check the psi this am and it held 15 at 3oclock today it was 11psi.When it was hot as heck outside and the truck was hot.

  ram head said:

Yea I believe the Texas heat may be the problem I check the psi this am and it held 15 at 3oclock today it was 11psi.When it was hot as heck outside and the truck was hot.

talking with the owner of fuel boss he informed me of this occurrence with hot fuel so i wasnt surprised to see 13 at idle when hot but 16-19 cold at idle. as long as pressure increases with rpm yer good!

Take the Bypass valve apart and check to see if it has some dirt in it. I had a similar issue when I installed mine, Richard at Glacier told me to check that and sure enough thats what it was

  • Owner

The only thing I don't like about it. Here in Idaho I see summer temps as high as 115*F and we all know about the heat soak issues with the VP44. The fact a mechanical pump is that low at idle bother me. Where my AirDog is nearly solid and never moves much from 17-18 PSI as of lately. In your case make sure to kick the idle up after starting hot to purge the heat from the VP44 you need to get above 14 PSI to get the overflow valve open.

i could take the spring out of the return valve from the fuel boss and shim it to get more pressure to push through the overflow valve in the vp.

I just put an Assissin pump on my rig this weekend and had read about a few guys who bought a larger gear so the pump was at a 1:1 ratio instead of the 1:2 ratio (guessing) it is at from the factory. This allowed them to maintain a higher idling pressure while still maintaining a safe WOT throttle pressure around 20psi. I haven't looked into it yet, but after test running mine yesterday at 12psi idle and 20psi WOT I am definately planning to do some more looking.

  • Staff

Pressure in my Fuel Boss dropped to 14 @ idle 16@ cruse and 21@ wot. I removed the fuel pressure regulator and found it stuck open. I blew through it the other way and pushed out what ever was holding the valve open. Now it's back to 19@idle and 21@ wot.

  IBMobile said:

Pressure in my Fuel Boss dropped to 14 @ idle 16@ cruse and 21@ wot. I removed the fuel pressure regulator and found it stuck open. I blew through it the other way and pushed out what ever was holding the valve open. Now it's back to 19@idle and 21@ wot.

do you have the smaller pulley on the pump? id like to have higher pressure and flow on mine. i have the larger pump pulley right now.
  CUMMINSDIESELPWR said:

do you have the smaller pulley on the pump? id like to have higher pressure and flow on mine. i have the larger pump pulley right now.

Change the shims in the bypass to give you higher pressures
    • Like 1

    My install went well with no issues. Nice quality system, good instructions - my fuel pressure doesn't fluxuate much. I see about 17 at idle and 18/19 @ 2k and @ WOT. I ran the tank lower than I usually do because I thought I would have to drop the tank and put in a draw straw, but with this system it wasn't necessary. I wasn't looking forward to dropping the tank.I called Richard on Sunday and left a message at his shop thinking he would return my call on Monday. I had a dumb question regarding the hobbs wiring harness and he returned my call within an hour - of course end user error on my side. Before I would see 10 at idle and 5 @ WOT with the factory set up.post-12101-138698208082_thumb.jpg

    post-12101-138698208074_thumb.jpg

      Quote

    I'm assuming Richard from Glacier Diesel ? Excellent customer service :thumbup2:

      Philo Beddoe said:

    My install went well with no issues. Nice quality system, good instructions - my fuel pressure doesn't fluxuate much. I see about 17 at idle and 18/19 @ 2k and @ WOT. I ran the tank lower than I usually do because I thought I would have to drop the tank and put in a draw straw, but with this system it wasn't necessary. I wasn't looking forward to dropping the tank. I called Richard on Sunday and left a message at his shop thinking he would return my call on Monday. I had a dumb question regarding the hobbs wiring harness and he returned my call within an hour - of course end user error on my side. Before I would see 10 at idle and 5 @ WOT with the factory set up. [ATTACH=CONFIG]6118[/ATTACH][ATTACH=CONFIG]6119[/ATTACH]

    Man that's awesome. :thumbup2: I wish my Assassin could do that... :banghead:
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