All fuel injected rx7's have a "pulsation dampner" on the end of their primary fuel rail. The goal of this device is to reduce hydraulic pressure surges when the injectors fire, since they fire exactly 180* out of phase with each other. The 86-88 n/a rx7 pulsation dampner is designed in such a way that makes it very easy for the rubber diafragm to tear, and gasoline to leak--almost directly onto the exhaust manifold!! This practically guarantees a huge gasoline engine fire, which is bad. Luckily, mazda redesigned the pulsation dampner in 89 so as to be integral to the primary fuel rail, and it really can't leak. It's a direct swap, and can be done in a few hours.

First, go ahead and get the 89 fuel rail/pulsation dampner, and try to get the mounting bolts along with it. Also, go ahead and get 2 or 3 feet of 5/16" *FUEL INJECTION* fuel line, and 6 hose clamps that fit that size. And, the lower->extention manifold gasket, and the extention->dynamic chamber gaskets wouldn't be a bad idea, either. New injector o-rings and grommets are also smart, or just send them off to be cleaned professionally.

Disconnect the battery first. Take off the intake. The TB, Dynamic chamber, and extention manifold. To take off the extention manifold, you'll have to remove the fuel hoses onto the secondary fuel rail, but that's fine, as you'll replace them anyway. Label EVERYTHING (both vacuum lines and bolts).

Un-bolt the primary fuel rail, taking extreme care not to lose the small oval plastic piece under it. The injectors should pull directly out of the block, and twist out of the rail.

Go ahead and test fit the new rail onto the block, minus the injectors. You'll see where the hoses will need to go, and their approximate lengths. I believe (from memory, so check it), you'll need about 6" from the rail to the feed, and maybe 8" from primary to secondary..maybe another 6" off the regulator to the return line.. But it's a real good idea to cut it long, then trim it down once you're sure you don't need it. Put the hoses on the primary rail now.

Replace the injector o-rings and grommets, and place a small amount of oil on the o-rings, to ensure a good seal. Twist the injectors into the new rail, hook the feed line up to the feed, and bolt the rail down onto the block. Be sure to remember the black plastic oval piece, for spacing. The 89 bolts should be used, as the 88 bolts are a bit too long, and you would need washers to compensate.

Now, you'll want to actually hook the hoses up to the secondary fuel rail, and to the pressure regulator, and pressure test the system. Reconnect the battery and turn the key on (don't try to start the engine..just turn the key to the "on" position). There's a little yellow connector near the FR strut tower. Short this. This will activate the fuel pump. You should hear the relay click, then hear fuel flowing, and the regulator bypassing it. Make sure there's no leaking. If there is, fix that first!!

Ok... no leaks. you're ready to bolt the manifolds back on. If you need to disconnect the fuel lines to do this, beware that the lines are now under some 40 psi of gasoline, and it may spray out when you pull the line. Be sure to use the new gaskets!

All done! Drive it around the block, make sure nothing is leaking still, and sleep well knowing your car probably won't catch on fire now.

Some side notes: While it's a direct swap, it's kind of a tight fit in places. The wiring harness sorta interferes with the PD, but it DOES fit. Routing the injector harnesses is a tad tricky, but realize that you can turn the injector around after it's mounted. Just find an angle that reaches. Also, the oil injector lines are RIGHT THERE, and are very, very brittle, so be careful with these. This is a very good time to replace the vacuum lines, as everything is off anyway.

Hopefully, i'll get some pics sometime.. Any picture donations, email to

*I make no claims as to the accuracy of this. It worked for me, it may not work for you. Don't sue me.*