fuel pump questions

[Super6]

i have a question to guys in the bottom 10's with 72lb or bigger injectors..who is running a single fuel pump in the tank ? thanks Bob

 

[TURBO 6]

Single pumps with dual alky nozzles are what the fastest alky cars have.

 

[2QUICK2B6]

X's 2

 

[Super6]

pressure

i must be doing something wrong then..i have two cars with the single pump and can't get enough fuel pressure to run the car out the back door..need around 70psi..best my car will get is 55psi and the other car goes to 55psi then back to 50psi..the one that drops back has a new walbro pump in it..my pump is a walbro with very few miles on it..maybe i need to ask about pressures? i am running dual nozzles for the alky but my buddys has the single nozzle on his..our fuel pressure is set at 38 plus 30lbs of boost i come up with needing 68psi at the rail..the reason i made this post it might save a few motors and i thought that running two alky nozzles would take the load off the single pump...i am rethinking this now......Bob

 

[TURBO 6]

I moved this thread here, figured you'd get more answers.

38#'s of pressure is static??

 

[Razor]

Sometimes its other stuff like power, ground, fuel filter, kinks in lines, etc.

If the fuel pressure is not keeping up.. you have to fix that. I chased an issue couple years ago and it was a bad hot wire relay. 3 head gaskets over that, 2 fuel pumps, 2 filters.. simple stuff first.

 

[87GN_70GS]

i must be doing something wrong then..i have two cars with the single pump and can't get enough fuel pressure to run the car out the back door..need around 70psi..best my car will get is 55psi and the other car goes to 55psi then back to 50psi..the one that drops back has a new walbro pump in it..my pump is a walbro with very few miles on it..maybe i need to ask about pressures? i am running dual nozzles for the alky but my buddys has the single nozzle on his..our fuel pressure is set at 38 plus 30lbs of boost i come up with needing 68psi at the rail..the reason i made this post it might save a few motors and i thought that running two alky nozzles would take the load off the single pump...i am rethinking this now......Bob

It's going to depend on your injector duty cycle. 72 lb injectors at 100% DC will exceed the capacity of a single in-tank 340. It's easy enough to check that on a pressure vs flow graph with both pump and inj on the same chart. You should be able to get away with 80-85% dc max.

 

[Razor]

My car at with 83's at 132 was at 60% DC

 

[Super6]

my duty cycle must be more than i think then...everything has checked out fine as far as the wiring and no kinks...i am going to throw another pump at it and see what happens..i am running a fat air fuel ratio...38 psi with the line off..that is what is recommended with my ME-R instructions for 72 pounders..i will get it ironed out..the faster you get the more stuff you need ..more $$.thanks for the help........Bob

 

[Super6]

Sometimes its other stuff like power, ground, fuel filter, kinks in lines, etc.

If the fuel pressure is not keeping up.. you have to fix that. I chased an issue couple years ago and it was a bad hot wire relay. 3 head gaskets over that, 2 fuel pumps, 2 filters.. simple stuff first.

you are correct..i have no room for error so if the pressure doesn't come up the boost is coming down..the car ran good on 24lbs..but 30lbs is where it's at...thanks Bob