Replacing The Fuel Pulsation Damper In Your Rx7

The fuel pulsation damper (FPD) in the Mazda RX-7 is prone to failure and can cause engine fires if not replaced in time. The FPD regulates the oscillation of fuel caused by the injectors' rapid opening and closing, preventing fuel hammer and stabilising fuel pressure. While some argue that the FPD is unnecessary, others emphasise the risk of engine damage and fires if it is not replaced regularly. The replacement process involves removing and working on various engine components, so it is important to have sufficient mechanical knowledge and experience.

Removing the upper intake manifold

To remove the upper intake manifold, you will need to first disconnect the battery. Then, remove the upper intake manifold (UIM), release the fuel pressure, and remove the fuel rails.

Before removing the UIM, you will need to remove the strut tower brace if you have one. Remove the air pipes that go from the air cleaner to the turbo inlets and the air pipe that runs from the turbos, past the alternator, to the intercooler. Remove the intake elbow pipe that attaches to the throttle body by removing its 4, 10mm chrome cap nuts, hose clamp, and 1 vacuum hose.

Next, remove the throttle body by removing the throttle cable, which can be done by rotating the throttle and sliding the throttle cable end out sideways. Then, remove the throttle body's 4, 12mm cap nuts, the coolant hose from the firewall side, the coolant hose from the bottom of the throttle body, and 1 electrical connector on the firewall side.

There are a lot of things attached to the underside of the manifold that will need to be disconnected before you can lift the manifold off. The extension manifold comes off by removing 5, 12 mm cap nuts, 2 bolts that hold down the solenoids under the manifold's front side, 1 bolt on the front left side (nearest the battery), and 2 bolts that attach the engine lift loop at the right rear side (there are two ground wires attached to these bolts).

There are also 3 electrical connectors that attach to the manifold. To remove them, push in the latch to allow the connector to slide off relatively easily. Do not force the connector without releasing the latch or you will break the connector. Lastly, there are about 5 vacuum hoses connected to the manifold, one connected to the "Double Throttle Actuator" (on the rear of the manifold) and one PCV (Positive Crankcase Ventilator) line that runs from the oil filler neck to the PCV valve to the front underside of the manifold.

Make sure to remember where all these components go so you can reconnect them later. You may want to label the hoses, sketch them, or take a picture of them before unplugging.

Releasing fuel pressure

First, locate the fuel pump connector. You can find detailed instructions on locating and accessing the fuel pump in the "Fuel Pump Removal Procedures" section of your RX7's manual. Once you have located the fuel pump connector, disengage it while the engine is running. The engine will eventually stall due to a lack of fuel. At this point, turn the ignition switch off.

Next, use a shop rag or a clean cloth to cover the fuel lines when disconnecting them. It is important to plug all fuel lines after they have been disconnected to prevent any fuel leakage. Make sure you have a safe and appropriate receptacle for any fuel that may spill during this process.

Now you can proceed with removing the fuel pump and servicing the fuel system. Remember to always relieve the fuel system pressure before performing any maintenance or repairs on the fuel delivery system. It is also important to wrap a clean cloth around the fuel connection when loosening it to catch any fuel spray from residual pressure. Take all necessary precautions to avoid the risk of fire.

Additionally, if you are planning to perform any maintenance or repairs that involve the fuel delivery system, it is recommended to raise the vehicle and support it safely before beginning work. This will provide you with better access to the fuel pump and fuel lines. Always refer to your RX7's manual for specific instructions and safety precautions related to your vehicle's fuel system.

By following these steps, you can safely release the fuel pressure in your RX7, ensuring a lower risk of injury or fire during maintenance or repairs involving the fuel delivery system.

Removing fuel rails

To remove the fuel rails of your RX7, you will first need to disconnect the battery. Then, remove the upper intake manifold (UIM), release the fuel pressure, and remove the fuel rails. Place the fuel rails on a clean, dry surface.

Next, you'll need to remove the primary fuel injectors. This may require some patience, but do not use a screwdriver as this will crack the injector connector. Try spinning the injector back and forth while pulling. Once the injectors are removed, you can take out the PD and secondary fuel rail fuel line.

Now that the primary fuel rail is stripped down, you will need to tap it. Place the flat portion of the fuel rail in a vice and use a 1/4-18 size tap to thread until it bottoms out in the fuel rail, ensuring you keep it as straight as possible. Clean the fuel rail using compressed air, WD-40, or similar, and ensure no shavings remain.

At this point, you can apply Teflon tape to the threads of a 5/16" Hose Barb x 1/4" (MIP Adapter) NPT fitting and screw it into the newly tapped fuel rail. Tighten it down completely with a wrench.

Now, inspect the O-ring on the secondary fuel line feed and replace it if it is worn. Reinstall it into the primary fuel rail and inspect the O-rings on the primary injectors, replacing them if necessary. Reinstall the primary injectors.

Finally, connect the fuel rails back to the fuel lines and reinstall them into the car. Reconnect the battery, prime the fuel system, and check for leaks. If there are no leaks, you're done!

Tapping the primary fuel rail

Step 1: Prepare the Work Area

Place the stripped-down primary fuel rail on a clean, dry surface. Ensure you have the necessary tools and materials, including a 1/4-18 size tap.

Step 2: Secure the Fuel Rail

Place the flat portion of the fuel rail in a vice, ensuring it is securely held in place.

Step 3: Start Tapping

Using the 1/4-18 size tap, begin threading into the fuel rail. It is important to keep the tap as straight as possible to ensure an accurate and straight thread. Continue threading until the tap bottoms out in the fuel rail.

Step 4: Clean the Fuel Rail

Once tapping is complete, thoroughly clean the fuel rail using compressed air, WD-40, or similar products. Ensure that all metal shavings and debris are removed to avoid any contamination.

Step 5: Install the Adapter

Take a 5/16" Hose Barb x 1/4" (MIP Adapter) NPT fitting and apply Teflon tape to the threads. Screw this adapter into the newly tapped hole in the fuel rail. Use a wrench to tighten it down completely, ensuring a secure and leak-proof connection.

By following these steps, you will have successfully tapped the primary fuel rail, ready for the next steps in the FPD bypass process. Remember to work carefully and methodically, ensuring all connections are secure and all surfaces are clean before proceeding.

Reinstalling the fuel injectors

Firstly, you will need to place the grommets in position on each injector. Then, put the o-rings on the injectors. Next, place the injectors back into the fuel rails. Oil up the injector o-rings so that they will seat in the fuel rails properly—this is very important. Put the diffuser o-rings on each diffuser, being careful as they are fragile. Then, place the insulators in the proper position.

Now, reinstall the fuel rails and reattach the fuel lines. Check for fuel leaks. Go to the diagnosis box, by the battery, jump the f/p and ground, to engage the fuel pump, and turn the key to the 'on' position. You should hear the gas flowing, and you should not smell anything.

Finally, reassemble the upper intake manifold (UIM) and all other parts that were removed.

Frequently asked questions