Rotary Resurrection - Tech Section
84-88 Fuel Pulsation Dampner Elimination
RX-7s made during this time frame had a small round device on the primary(lower) fuel rail called a pulsation dampner, or PD or FPD for short. Often these fail allowing raw fuel to be shot out, which then runs down the side of the engine onto the hot exhaust manifold. Many junkyard rx-7s died a fiery death because of this, and many owners have had their cars catch fire spontaneously due to this. IF you remove the yellow plastic cap and find that the screw has come out and is laying in the cap, your PD is ready to fail and must be replaced. FC turbo model shown, the PD on nonturbo engines is on the front of the lower rail, behind the alternator.
It is highly debated on the various rotary forums as to whether or not a PD is actually necessary for a stock or mildly modified rotary. Mazda engineers obviously thought it necessary, but such can also be said for such ill-fated systems as the subzero starting assist bottle, the 89-91 automatic sliding seatbelts, and other poorly designed systems.The safest thing to do is probably to buy a new PD from the dealer at a cost around $85-150, but then again that new part could very well fail within 5 years.

However, there is a simple and cheap permanent fix with no *proven* side effects for the owner who wants to take the time to correct the condition. I have personally performed this repair on several of my own and customers cars with no noticeable issues. Here are directions:

Obtain a spare primary fuel rail from an 86-88 non turbo engine. Note the FPD on one end, (the larger mushroom shaped part) and the banjo bolt on the other end(hollow bolt). Remove the banjo bolt (banjo bolt size is 12mm x 1.25) and discard the rail.

Remove the primary rail from your car. You will need to remove the upper intake, middle intake(nonturbo models), and assorted hoses, cables, and wires to do so. The lower fuel rail is bolted to the pass. Side of the block, where the intake mates to the engine.

Remove your FPD from your fuel rail.

  install the banjo bolt you removed from the spare rail into your rail. Be sure to use both copper crush washers and tighten this bolt down well.
  Put it all back together. Be sure to get the fuel lines and injectors seated and tight, and inspect for leaks.
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