Major Fuel Drop Problem
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On The Tree
Joined: Jul 2002
Posts: 131
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From: tampa fl.
Major Fuel Drop Problem Here's what I had... 346 ATI Procharger 11psi forged bottom end. Made 575 rwhp with no fuel problems. The fuel systems was (2) 255 fuel pumps, 5/16 lines going into a "T" out to stock line to a SX fuel filter to stock line to stock fuel rails. I removed the regulator from stock sending unit and put a SX regulator boost reference in the rear right past the "T" block. It worked fine with no problems.
Here's what I have now... 408 Heads, huge cam, same blower set-up (for now). Went to the Dyno today -- fuel pressure was steady at 60psi (1st pump) the second pump kicks in with a hobbs switch at 4psi or wide open throttle (which ever happens 1st). As soon as we got in it hard the fuel pressure dropped from 60 to 40 instantly. It seamed to recover and then it tapered back slowly -- we obviously let out.
Everything from the pervious set-up was the same except from the fuel filter forward I ran 1/2 line to aeromotive fuel rails out of rail 3/8 to SX regulator and stock line return to fuel.
I have a theory that the fuel filter is housing the greater amount of fuel and from the fuel pumps to the fuel filter is actually a restriction and can't fill the fuel filter fast enough to supply the 1/2" lines and rails.
I was wondering what I might need to do to correct the dropping fuel pressure -- a friend suggested that I should replace the 1/2 line with 3/8 line and said that that should work.
Any suggestions would help...I know that I can't be the first person to do this. By-the-way, this set-up 547 @ 4000 rpms and 5 lbs boost -- I don't know if the fuel pumps are big enough to support the new set-up.
Here's what I have now... 408 Heads, huge cam, same blower set-up (for now). Went to the Dyno today -- fuel pressure was steady at 60psi (1st pump) the second pump kicks in with a hobbs switch at 4psi or wide open throttle (which ever happens 1st). As soon as we got in it hard the fuel pressure dropped from 60 to 40 instantly. It seamed to recover and then it tapered back slowly -- we obviously let out.
Everything from the pervious set-up was the same except from the fuel filter forward I ran 1/2 line to aeromotive fuel rails out of rail 3/8 to SX regulator and stock line return to fuel.
I have a theory that the fuel filter is housing the greater amount of fuel and from the fuel pumps to the fuel filter is actually a restriction and can't fill the fuel filter fast enough to supply the 1/2" lines and rails.
I was wondering what I might need to do to correct the dropping fuel pressure -- a friend suggested that I should replace the 1/2 line with 3/8 line and said that that should work.
Any suggestions would help...I know that I can't be the first person to do this. By-the-way, this set-up 547 @ 4000 rpms and 5 lbs boost -- I don't know if the fuel pumps are big enough to support the new set-up.
I would check out the wiring, the voltage directly across
the pump motor terminals if you can get at it. Why two
pumps running, into / out of the same restrictions would
show less flow than one makes no "plumbing sense" to me.
But a more gradual roll-on might show up more clearly
whether this is an instant drop that attends the second
pump coming on line, or a gradual flow/pressure fade that
just looks as fast as the injector flow ramp-up.
the pump motor terminals if you can get at it. Why two
pumps running, into / out of the same restrictions would
show less flow than one makes no "plumbing sense" to me.
But a more gradual roll-on might show up more clearly
whether this is an instant drop that attends the second
pump coming on line, or a gradual flow/pressure fade that
just looks as fast as the injector flow ramp-up.
