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.*