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Using a TBI pump with a carb

thebigdaddyof2

thebigdaddyof2

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I know this was just recently talked about but I have an idea I wanted to run by you guys.
If you use a carb'd motor in a vehicle with a TBI pump, I am aware that you can run the Mallory 4309 regulator with the return port and it will work just fine.

But, (if you're cheap like me), could you instead use a generic fuel regulator plumbed from a "tee" installed between the OEM feed and the return fuel lines?

Think this would work?
 
No because all your fuel will take the least path of resistance, so it will all end back in the tank.

Dan
 
yes, if you use a non return port style regulator plumbed off a tee fom the main feed line, that would also work, but only if the generic regulator could stand the constant pumping of 15 psi at its door, i think it may be too much for one.
 
if the reg is doings its job what would create this constant 15psi you refer to?
pumps just pump, restriction makes pressure
 
I already thought about the least path of resistance but, how does a bypass/return system work then?

MJ, how does the OEM system generate 12-15psi with a bypass/return?
 
If you used 2 generic regulators it would work wouldn't? Run one regulator on the sending line and one on the return line. This would keep pressure to the carb wouldn't it?

The if the first regulator was set at 6 psi and the return line reg was 5 psi it would keep 5 psi in the system for the carb to run off and anything over 5 psi would go back to the tank. /forums/images/graemlins/dunno.gif
 
Just a thought, but if you're using a regulator to reduce the pressure to the carb, why would you need to still use the return line? I would think in this application, you might be able to plug off the return line.
 
A "standard" 3 port regulator works fine. I have it on 3 trucks.

Plumb the gas tank feed from the pump to the inlet port.
Plumb the carb to one outlet port
Plumb the other outlet to the return line.
Put a small hose clamp on the return line to regulate the amount of fuel you want going into the return line. (tighten on rubber hose)

I have had this setup on one truck for 4 years with no issues. The others a couple. Works fine, Really. /forums/images/graemlins/waytogo.gif

You must use a return line on the intank pump, or it will burn up in short order.

John
 
[ QUOTE ]
if the reg is doings its job what would create this constant 15psi you refer to?
pumps just pump, restriction makes pressure

[/ QUOTE ]

How can a regulator increase pressure?

How does restriction INCREASE pressure?

Last I checked, fluid was a lot like electricity. Same pressure (voltage) but more restriction (resistance) = LESS flow (current) last time I checked, unless I am missing something here.
 
Sounds like you need to learn a little about basic hydraulics. /forums/images/graemlins/thinking.gif
 
[ QUOTE ]
Sounds like you need to learn a little about basic hydraulics. /forums/images/graemlins/thinking.gif

[/ QUOTE ]

So smaller tube is going to increase pressure? How?

I'm actually curious, i've never heard anything like that before.
 
You ever capped a garden hose with your thumb? What happens to the pressure in an exhaust system when you add a more restrictive muffler, etc?
 
[ QUOTE ]
You ever capped a garden hose with your thumb?

[/ QUOTE ]

More pressure to achieve less volume. I'm starting to get it now.

[ QUOTE ]
What happens to the pressure in an exhaust system when you add a more restrictive muffler, etc?

[/ QUOTE ]

More pressure required to push out the spent gasses and less horsepower. /forums/images/graemlins/thumb.gif
 
I'm using this Mallory Regulator on mine Reg. Pic & Spec.s
I had TBI and the fuel pump can develop 45 psi not 15.
I can dial it in to any pressure I want. It works great.
It's a #4309 and I have a small ball valve on one outlet so I can hook up a hose to pump gas to another truck if needed or hook up a gauge. The return line is required to regulate pressure or it would build up and only go down to it's setting when actually in use. This would damage your carb.
I think it's cheap compared to carb damage or a huge fire under your hood. Get a grip and spend the money. Don't burn.
 
sorry didnt come back here til now.
this subject always gets me flamed and I wasnt into the headache again /forums/images/graemlins/smile.gif

I do not recall where to find it but you can plumb a standard blue Holley reg as a return style regulator

a mechanical fuel injector jet can uses a check ball and an adjustable tension spring to maintain set pressure.
we use a variation of that combined with nitrogen pressure and air timers to vary the fuel pressure during the run in the nitro bike.

I am pretty sure that is the basis of the EFI regulators as well only they use a diaghram rather them stainless checkballs
the SEFI that have the injectors downstream of the throttle plate also have the regs vacuum referenced
IIRC the pressure is maintained in the line all the way from the pump to the reg and any excess is bled out the return with the injector being between pump and reg
rather then the pump deadheading until the pressure drops in a line.
the traditional deadhead way seems to require 2 regs, one to save the pump motor and one to regulate the fuel supply.
newer deadhead systems use a controller to turn the pump down or off when little fuel is needed

my going back and adding snippets in that post probably made it incoherent
 
from faded memory I think you just plumb the reg backwards

guessing here so dont quote it /forums/images/graemlins/smile.gif
line from pump to carb has a T in it that feeds to normal outlet of the reg
normal inlet of the reg becomes the return

sorry Rene I typo'd again
 
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