Fuel Cutoff Switch (Anti-Flood)
and Unflooding Procedures
Many older 2nd gen rx-7s suffer from a condition referred to as flooding.
This happens as an engine gets worn out, its compression drops lower and
lower, and it becomes hard to start especially when warm(short trips).Even
though there may not necessarily be an excess amount of fuel in the combustion
chamber, the condition of hard starting or no starting on a rotary is
referred to as flooding. Note that though it is possible to flood any
rotary, only the 2nd generation suffers from this chronic problem in general.
Also note that the 89-91(series 5) rx-7s have a built-in flood protection
system and do not flood as much as the earlier 86-88 models. The series
5 flood protection is very easy to use: floor the gas pedal while cranking
the car over to CUT fuel to the engine and thereby unflood it(if lightly
flooded). IT is possible to flood a series 5 to the extent it requires
an unflooding procedure outlined below.
Note that fresh rebuilds(using old rotor housings with imperfect sealing
surfaces) often have very low compression in the beginning(under 1500
miles) and may require unflooding until compression builds up within spec.
Use these same procedures in this case. Installation of a fuel cut switch
is also recommended for the breakin period.
a lightly flooded 2gen:
Remember that you don't need to do this step for an 89-91, just floor
the gas while cranking to duplicate this effect. The below instructions
are for 86-88s.
1) raise hood
2) remove underhood fuseblock cover
3) remove EGI fuse closest to engine
4) Crank the car over for 5-10 seconds, 2-3 times. Car may start and die,
or might sputter as if to start.
5) Replace the egi fuse
6) Quickly get back inside the car and start it up. IF usually helps to
floor the gas at this time.
IF this doesn't start your car, proceed to the next phase…
Unflooding a heavily
There are a few different ways to go about this, depending on which model
and year of car you have. The tried and true method entails the following:
1) remove BOTH EGI fuses closest to engine in fusebox
2) remove plugwires and lower plugs
3) crank the car over 5-10 seconds with plugs out to expel extra fuel
4) obtain some ATF(automatic trans. Fluid) or motor oil along with a method
to inject it to the lower plugholes of both rotors. This will mix with
the excess fuel, rebuild compression momentarily, and help the car restart.
I use a hand oil pump available at autozone, which fits in a gallon jug.
You can also use a small oil can with a vacuum hose, or a funnel with
a long hose. Be sure to get enough in the first time, you don't want to
have to keep repeating this step. You cannot really put too much atf in,
as you cant hydrolock a rotary. The excess will just get shot out the
exhaust port. About 1⁄2 cup per rotor should be more than enough.
5) Dry plugs and clean them with a wire brush, or just put a lighter to
the electrode to remove gas fouling.
6) Replace plugs and wires.
7) Replace fuses.
8) Crank car to start. Floor the gas when doing so. Expect a lot of smoke.
This is the
hard way to do the job, but it will always work. Depending on your year
and model it may be possible to use an easier method:
NON TURBO models can utilize a single vacuum hose to inject the atf/oil.
In fact there are 2 locations to do so. You can not use a funnel in these
methods, you will need a pump to force fluid in.
1) Locate the upper intake manifold, the ribbed aluminum casting that
has 13B injection printed on it.
2) On the front end of that intake are 3 vacuum hoses. One is larger than
the other 2, the larger one is on top.
3) Remove the larger one. You're going to pump the atf/oil into this HOSE
slowly. This hose splits into 4, and leads to all the oil injectors on
the block, which inject directly into each combustion chamber. Doing this
will not interfere with the oiling duties of the oil injectors later.
4) Pump slowly when doing this, as these are small orifices youre pushing
5) 3-4 pumps should do it. Replace the hose and start the car.
The other method for 86-88 NT's:
1) On the same upper intake, on the drivers side, there is a large vacuum
hose(about 1") leading in below the BAC. Above that is a small, 3mm
2) Remove it, you can pump into this nipple, which will squirt atf/oil
into both primary intake runners evenly, though this method might require
more atf to be injectors(to run down into the engine) and longer to work(to
allow time to traverse the length of the intake).
A method for 87-91 turbo
1) Locate the upper intake manifold, passenger side, and the BAC valve
(round piece mounted on its side).
2) Above the BAC is a ? shaped hose. Remove it.
3) You can pump into this hose(downward into the upper intake/BAC) which
is evenly divided between both primary intake runners, and it will run
quickly into each chamber. 4-5 pumps will be enough. You can also use
a funnel and hose for this one, as there is no restriction in this hole.
Method for 89-91 nonturbo engines has not yet been found to be practical.
IT is best to do the sparkplug method unless you feel like loosening the
upper intake manifold and pumping directly into the intake runners.
Fuel cut off switch
The "band aid" cure for cars which flood consistently is to
install a toggle switch which will control the fuel pump. Note that the
only cures for consistent flooding are cleaning/rebuilding injectors,
rebuilding the engine, or finishing rebuild breakin. I like to install
my cutoff switch right behind the keyhole in the lower column surround,
but anywhere within easy reach will work. I use a toggle switch available
at radio shack for about 2 dollar, called a rocker switch. IT is solid
black, very slimline(maximum protrusion 1/8") and fits perfectly.
You can use any toggle switch however.
1) Obtain the following: 2 prong, 2 position toggle switch, at least 2
feet length of 16-14 gauge wire, 2 female speaker terminal connectors(quick
connect), 2 wire taps(vampire taps) and wire crimpers/strippers. Vampire
taps join one wire beside another, when a metal strip gets pushed down
connecting the 2 wires. A clean way to connect 2 wires.
2) Remove column cover and install the toggle switch in its position(or
wherever else you want).
3) Locate the fuelpump relay under the dash. Located between the radio
and the steering column, it is a black relay with a white, 5 wire plug.
4) Cut the fuelpump control wire: of the 5 wire plug, cut the middle wire
of the 5.
5) Run wires from the toggle switch to each of the ends you just cut and
connect them all. Which wire goes to which end does not matter, there
is no polarity here, only continuity.
6) Put everything back together. Your switch is now installed.
7) To operate it, figure out which way is on and which is off. I like
to orient off downward.
8) With the car running, flip the switch off and allow the engine to stall.
Remove your key, and leave the switch off. The fuelpump cuts off, and
the engine drinks all the fuel in the line until it is gone, which means
there is none left to flood the engine later.
9) When restarting, insert key, crank car, and flip on switch WHILE cranking.
The fuelpump will come to life, shoot fuel into the engine, and it will
start normally. Flooring the gas is sometimes helpful but not required.
10) Some cars may even start for a second before the switch is flipped,
from residual fuel in the rail. In this case, the procedure should be
to insert key and turn, car will start, then flip switch on immediately
to keep it running.