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Discussion Starter #1
So just go home from the dyno and the tuner said its running out of fuel as the fuel pressure isn't going up as the boost increases. He said it could be either the pump or the regulator. So I was wondering if there is a way to confirm which one it could be.

here is my setup

5.4 DOHC
Novi 2k
Walbro 465 pump intank (3/8 flex hose to 8 AN union bulkhead fitting then 8 AN to the regulator)
Edlebrock fuel regulator. 6 AN holes but I put a 6 to 8 union fitting going to the rails
5/8" rails
60lb injectors
HPX slot sensor in a 3" tube
6 an return

Car made 546rwhp uncorrected at 5,900 where the fuel pressure dropped like a rock. At this rpm it was with 8psi with 15* timing.

This walbro should have no problem supporting that power. Using various calculators on the net I thought it could support at least 600rwhp.

Or could the regulator be too small or not working properly? When idling if I blip the gas the pressure does move.

Thanks.

-Mark
 

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My guess is you are maxing out the fuel injectors. 60's are marginal at best at that power level.
 

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Discussion Starter #3
My guess is you are maxing out the fuel injectors. 60's are marginal at best at that power level.
Figuring a BSFC of 0.6 and running the 60's at 43.5 fuel pressure, which is the FP they are rated at: 60#, they will support roughly 800 HP at the crank.

Thats close to 700rwhp.

I think they should be enough injector for 550rwhp. I wonder if the wires to the pump need to be upgraded. Maybe I'm not getting enough juice to it.

-Mark
 

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How is the fuel lines routed? You should have fuel line from tank go to y block in engine compartment, to front of fuel rails, out of rear of fuel rails to regulator. All of that should be minimum of -8. A -6 from regulator back to tank is ok. It is also ok to go from y- block to back of fuel rails, then out from front of rails to regulator.
 

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you measure press before and after the reg

if they are the same when press drops

the reg is fine and must look elsewhere

if you think wires to pump are an issue you check for a voltage drop across the length of each wire
 

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Discussion Starter #6
How is the fuel lines routed? You should have fuel line from tank go to y block in engine compartment, to front of fuel rails, out of rear of fuel rails to regulator. All of that should be minimum of -8. A -6 from regulator back to tank is ok. It is also ok to go from y- block to back of fuel rails, then out from front of rails to regulator.
I followed the stock routing (down the subframe, right at the tranny tailshaft then down the tunnel to the diff).

The Line comes from the fuel hat (8an) all the way to the regulator in the engine bay. Then other side of the regulator goes to the rails (maybe a foot long). The regulator has 6 an ports so I wonder if that is the choking point.

But to be on the safe side I will rewire the pump.


you measure press before and after the reg

if they are the same when press drops

the reg is fine and must look elsewhere

if you think wires to pump are an issue you check for a voltage drop across the length of each wire
how would I measure that?
 

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You need to go through the fuel rails first and then the regulator.
 

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You may have to drop the fuel tank and check the rubber hose from the fuel pump to the fuel hat may have a hole in the hose.
 

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You need to go through the fuel rails first and then the regulator.
Not really. You can feed the regulator first then the fuel lines. More people are switching to this method b/c it allows the unnecessary fuel to be returned to the tank w/o having to enter a hot engine compartment which helps keep the fuel in the gas tank cooler. Mines done this way and works great.

ks
 

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Discussion Starter #10
Ok, sanity check. Stock voltage system for my car is 13.5v right? thats what the alternator charges the battery at I think. So by hooking up the pump to the factory wiring "should" mean its at 13.5 volts right?

I have a feeling that this pump is operating at a lower voltage.

But with respect to where the regulator resides.... I think all of the LSx cars are fueled with the regulator on the feed side. Like Kevin said, not reason to pump all that fuel through the rails if its not needed.

-Mark
 

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-6 an regulator. Adapting up to -8 from -6 does nothing. I overbuilt my fuel system so I would not have issues like this. Build right the first time.
 

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Boost reference regulator? If so you can use a regulated air source to verify fuel pressure increase without having to be on a dyno or driving. Also check gph rating of your pump. Unhook a fuel,line after the regulator and do a timed run with the fuel pump running. That will tell you if it's pump, also are your filters rated to flow enough etc etc. As for voltage drop to the pump, I always run a bigger gauge wire to the rear and use a relay with the factory hot wire as the switching wire for the relay.
 

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He has two threads over on Yellowbullit about this issue...still has not received the answer he wants.
 

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Discussion Starter #16
Boost reference regulator? If so you can use a regulated air source to verify fuel pressure increase without having to be on a dyno or driving. Also check gph rating of your pump. Unhook a fuel,line after the regulator and do a timed run with the fuel pump running. That will tell you if it's pump, also are your filters rated to flow enough etc etc. As for voltage drop to the pump, I always run a bigger gauge wire to the rear and use a relay with the factory hot wire as the switching wire for the relay.
Yes it is. 1:1. The inline filter is the standard 10 microns. Its brand new. I am going to wire the pump directly with a relay and see if that works. But before I test it, I'll see if I can hot wire the pump bypassing engine start up and see how much fuel it dispenses in say 30 seconds. Then if the pump is not the problem, I'll try moving the regulator to the return side.

Thanks.
 

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Yeah thats it. :rolleyes: Once you said 60's are marginal for 550hp I had all the answers I needed.....from you.
And yet you still have the same problem...but I digress. I did mention a few other things, but they could not be the issue either...lol
 

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testing a pump's volume against no pressure is a relatively useless test

looking for a pressure drop under load, is better
 

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Wait - are you running a 465 on stock wiring? If so, that's your problem. My HPF 320 lph supported 700 fwhp before dropping pressure. My Walbro 465 is supporting roughly 860 fwhp, running at base FP of 50 psi and hitting a duty cycle of 85% on 80 lb injectors and pressure is holding solid.

I'm going to assume you have a 5 speed - that's important info when talking rwhp and fuel system issues. FWHP, or even better base FP and duty cycle is much more accurate.

I run 10 gauge wiring straight from the trunk mounted battery, to a trunk mounted relay to the pump. And be sure to run 10 gauge for the ground, too. If you keep the runs as short as I did you could probably get away with 12 gauge, but why risk it?
 
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