AEM 25-304BK Honda/Acura Adjustable Fuel Pressure Regualtor - Manual (Page 7)

The AEM adjustable fuel pressure regulator has been set to 40psi using a
typical Honda fuel pump and a perfect running fuel system. Due to the
differences on vehicle fuel pressure on different applications it is highly
recommended that you adjust the fuel pressure on your vehicle. Refer to the
last page of the instructions for the factory recommended fuel pressures.
WARNING!!!
3) Stock fuel pressure regulator removal
a) Place a rag or shop towel under the fuel pressure regulator return line.
b) Disconnect the fuel return line at the bottom of the stock fuel pressure regulator.
c) Disconnect the vacuum hose from the stock fuel pressure regulator.
d) Place a rag or shop towel over the fuel pressure regulator.
i) Remove the two 6mm retaining bolts.
ii) Remove the fuel pressure regulator from the vehicle.
4) Installation of the AEM adjustable fuel pressure regulator
Note: The AEM fuel pressure regulator has the .100” orifice installed in the regulator and is set to
40psi. All adjustments of the pressure regulator will be explained in a later portion of the instructions.
a) Remove and discard the two fuel pressure regulator caps used in packing.
i) Note: One cap is in the fuel inlet and one cap is on the fuel return.
b) Install the fuel pressure regulator onto the fuel rail using the two allen bolts and washers supplied in the kit.
Make sure that the o-ring is replaced and properly installed between the regulator and the fuel rail .
i) Note: When installing the two allen head bolts a 5mm allen key should be used.
ii) Torque to 9 lbf-ft.
c) Connect the vacuum hose to the top of the fuel pressure regulator. On some vehicles incorporating a
strut tower brace, it may be required to rotate the pressure regulator top to clear vacuum fitting.
d) Install the fuel return line fitting.
i) Use one crush washer when using the inline return fitting. Tighten to 20 lbf-ft. (Kits 25-300 & 25-301)
ii) Use two crush washers (one on each side of the fitting) when using the banjo angle return fitting.
Tighten to 20 lbf-ft. (Kits 25-303 & 25-304)
(1) When using a kit with an angle return fitting, rotate the return nipple to match the fuel return line
placement before tightening.
e) Make sure that the rubber fuel return line is free flowing back to the fuel return hard line.
(1) Note: Ensure that there are no bends or kinks in the line that can restrict the fuel flow.
f) Install any remaining components that were removed during disassembly.
5) Finishing touches
a) Connect the negative battery terminal.
b) Turn the ignition switch to the on position for approximately two seconds. Do not operate the starter.
Then turn the ignition switch to the off position.
c) Repeat this procedure three times, and then check all components that were removed during installation for
any signs of fuel leakage.
d) If there are signs of leakage you MUST correct the leak before proceeding.
e) If there are no signs of leakage, then start engine and again check for leaks. If there is any sign of leaking
you MUST repair the leak before driving the vehicle.
f) Note: To check the fuel pressure, start the engine. Measure the fuel pressure with the engine idling
and vacuum hose of the fuel pressure regulator disconnected from the fuel pressure regulator and
pinched. Set the AEM adjustable fuel pressure regulator to recommended settings on the last page
of the instructions.
6) Pressure and orifice adjustments
Note: The AEM adjustable fuel pressure regulator can be fine tuned for your application. These
adjustments will be covered in this section. A fuel pressure gauge needs to be used for precise tuning.
a) When fuel pressure adjustments are to be made, loosen the jam nut on the top of the AEM fuel pressure
regulator and either tighten or loosen the set screw.
i)
When loosening the jam nut a 3/8” wrench should be used.
ii) When tightening or loosening the set screw a 3/32” allen key should be used.
(1) To increase fuel pressure turn the set screw in a clockwise rotation.
(2) To decrease fuel pressure turn the set screw in a counter-clockwise rotation.