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FORM 1078 (Rev B) 01/12
INSTALLATION INSTRUCTIONS
3-PORT COMPETITION
FUEL PRESSURE REGULATOR
(RETURN STYLE)
PART NO. 4309
NOTE: DO NOT RUN THIS PUMP WITHOUT FUEL (EXCEPT FOR BRIEF PERIODS WHILE PRIMING).
IMPORTANT: This regulator must use a fuel return line. The fuel return line runs between the fuel return port of the regulator and the fuel
tank. Fuel pressures cannot be adjusted if the fuel return line is absent.
PART INCLUDED IN THIS KIT
1 3-Port Fuel Pressure Regulator
1 Bracket
2 Bracket Mounting Screws
1 Bypass Spacer (to modify COMP PUMP® 110 and 140 Series
Electric Fuel Pumps)
SPECIFICATIONS:
Port thread sizes (ALL): 3/8” NPT
Adjustment range: 3-12 PSI (approximate)
Fuel Application: Gasoline, Automotive/Street and Racing
applications
GENERAL INFORMATION
Mallory’s 3-Port, return style regulator regulates fuel pressure between high pressure fuel pumps and carburetors. The
regulator is recommended for Mallory COMP PUMP® 110, and 140 Series Electric Fuel Pumps.
NOTE: This regulator is not recommended for pumps over 200 gallons per hour.
By returning excess fuel and fuel pressure to the fuel tank, this regulator benefits fuel pumps in several ways. The fuel pump will run
cooler, draw less current and will always have full volume output available at the pressure setting. The fuel return line runs between
the fuel return port of the regulator and the top of the fuel tank. The fuel tank must have
provisions for a fuel return line.
This regulator is equipped with a vacuum/boost compensation port (brass barb fitting) that can be used tomomentarily decrease
fuel pressure (vacuum compensation) at idle and part throttle, or increase fuel pressure under blower boost (boost compensation).
While it is not necessary to connect a hose to the vacuum/boost compensation port, it may be
beneficial in some cases. However, the small plug on the barb must be removed before use.
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MALLORY COMP PUMP® 110 AND 140
SERIES ELECTRIC FUEL PUMP SUGGESTED
MODIFICATION ONLY WHEN USING RETURN STYLE
REGULATORS(See Figure 1)
Step 1
Release the jam nut on the bypass plug. Remove the
bypass plug. Remove the bypass spring and plunger. Save
the bypass spring for possible future use.
Step 2
Inspect the bypass plunger. The bypass plunger surface
should be clean and slide freely in the chamber. Check
the bypass plunger pad and remove any debris embedded in its surface.
Step 3
Install the bypass plunger pad in the bypass plunger.
Install the bypass plunger and bypass spacer. Clean the
bypass plug.
Step 4
Apply thread sealant compound on the bypass plug.
You can find thread sealant compound at a hardware
store. Do not use thread sealing tape.
Step 5
Install the bypass plug. Gently tighten bypass plug until
you feel it lock (torque to 5 in/lbs). Install and tighten the
jam nut.
FIGURE 1
MOUNTING PROCEDURE
The regulator may be mounted at any angle. For maximum efficiency, mount the regulator as close as possible
to the carburetors.
DO NOT mount the regulator on or near exhaust manifolds. A bracket is provided for convenient mounting
under an intake bolt.
FITTINGS, FUEL LINES AND FUEL RETURN LINE
The fuel return line should be as large, or larger, as the
fuel line between the fuel pump and the regulator. See
Figure 3.
Purchase fittings (and plugs). Use a thread sealant
compound on the fitting threads. You can find thread
sealant compound at a hardware store. Do not use
thread sealing tape. Install the fittings. Do not overtighten the fittings. This could damage the regulator.
Connect the fuel lines and fuel return line. See Figure
3A-3C.
FIGURE 2
FUEL RETURN LINE SIZE
RECOMMENDATIONS
Fuel Return Line
Length/ Distance
16 – 20’
11 – 15’
6 – 10’
1 – 5’
3/8” = #6AN 1/2” = #8AN 5/8” = #10AN
FUEL PUMP GALLONS PER HOUR (FREE FLOW)
1 TO 99 100 TO 129 130 TO 199
1/2” 1/2” 5/8”
3/8” 1/2” 5/8”
3/8” 1/2” 1/2”
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FIGURE 3A
FIGURE 3B
FIGURE 3C
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FUEL PRESSURE ADJUSTMENT
NOTE: It is not necessary to have the engine running
while setting fuel pressures with this type of regulator.
DO NOT exceed the fuel pump manufacturer’s maximum
recommended operating pressures. This could damage
the fuel pump. (See Figure 4 for Mallory COMP PUMP
® Series Electric Fuel Pumps maximum recommended
operating pressures.)
Step 1
Remove and discard the plastic cap on the vacuum/
boost compensation port. Release the jam nut on the
adjustment screw. Remove the adjustment screw.
Step 2
With the engine off, turn on the fuel pump. Check the
fuel system for fuel leaks. Check the fuel pressure with
the adjustment screw removed. The pressure must be
less than 3 psi. If not, a less restrictive return line must be
used. Turn off the fuel pump and correct any fuel leaks
before proceeding. Install adjustment screw.
Step 3
Adjust fuel pressure. Check the fuel system for fuel
leaks. Turn off the fuel pump and correct any fuel
leaks before proceeding. Install and tighten jam nut.
VACUUM/BOOST COMPENSATION POR
While it is not necessary to connect a hose to the vacuum/boost compensation port, it may be beneficial in
some cases. The vacuum/boost compensation port can
be used to momentarily decrease fuel pressure (vacuum
compensation) at idle and part throttle, or increase fuel
pressure under blower boost (boost compensation).
Connect a hose between the vacuum/boost compensation port and a carburetor or intake manifold vacuum
port to vacuum index the regulator. The set pressure of
the regulator decreases about 1 PSI for every 2 inches
Hg (2 inches on the vacuum gauge). Connect a hose
between the vacuum/boost compensation port and an
intake manifold boost port to boost index the regulator.
The set pressure of the regulator increases 1 PSI for every
1 PSI of boost.
NOTE: DONOT exceed the fuel pump manufacturer’s
maximum recommended operating pressures. This could
damage the fuel pump.
REGULATOR SERVICE PARTS:
D IAPHRAGM KIT, G ASOLINE, FO R
REGULATOR PART NO. 4309.
KI T
PART NO.
3156
FIGURE 4
MAXIMUM OPERA TING
PRESSURE
COMP PUM P ® SERIES
110 14 0
7 PSI 14 PSI
MALLORY IS A TRADEMARK OF PRESTOLITE PERFORMANCE
10601 MEMPHIS AVE. #12, CLEVELAND, OH 44144
216.688.8300 FAX 216.688.8306
MALLORY IGNITION www.mallory-ignition.com
FORM 1078
(Rev B) 01/12
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