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Démarrage et Inondation (Flooding)

Source : RX8Club.com - New and Potential Owners START HERE! Auteur : RIWWP

Flooding — Qu'est-ce que l'inondation et comment la résoudre​

Another major complaint about the RX-8 is the tendency to "flood".

Qu'est-ce que le flooding ?​

Flooding, per the rotary engine term, is when there is too much gasoline in the combustion chamber. This really only happens when driver attempts to start the engine, but the engine doesn't immediately start. The ECU is pumping fuel while the engine is cranking, and if the engine doesn't start up quickly enough, all this fuel just soaks the plugs, washes around in the housing, and keeps the ignition from actually firing.

Flooding is only a concern if you have a weak ignition system, failing compression, failing battery, and/or failing starter.

Every single flood I have seen reported ended up coming down to one of these failing: Battery, Starter, Coil(s), Plug Wire(s), Plug(s), and/or Engine Compression.

  • If it's the battery that failed, the starter can't spin the engine fast enough, so the engine won't get good enough compression, and the air/fuel mixture won't ignite with any force.
  • If it's the starter that failed, the starter can't spin the engine fast enough, so the engine won't get good enough compression, and the air/fuel mixture won't ignite with any force.
  • If it's the engine compression that has failed, the engine won't get good enough compression, and the air/fuel mixture won't ignite with any force.
  • If it's the coils, plug wires, or plugs that have failed, it doesn't matter what compression you can achieve, what engine speed you can reach, you need a spark to light the air/fuel mixture!

Stay on top of the maintenance (long term included!) and you will wonder what all the fuss was about. Coils, plugs, and wires, should be replaced every 30,000 miles, possibly sooner if you detect something starting to fail, since people have had them fail as early as 8,000 miles or 15,000 miles, though that's rare. You can replace them for as little as about $200.

You don't want to shut off while it's cold simply because when the engine is cold, the ECU dumps more fuel into engine to help it warm up, and it leans back once the engine is warm. This extra fuel can make it harder to start an ignition, which a healthy ignition system is perfectly capable of overcoming. Weaken the ignition with failing plugs, coils, wires, alternator, starter, or battery, and you have a flood on your hands, and all the associated problems from that.

Comment résoudre le flooding ?​

There are many methods, but the method you should always try first is what Mazda has built into the ECU logic:

  1. Hook up another running car to the RX-8's battery with jumper cables to keep the battery from dying.
  2. Hold the gas pedal to the floor (this signals the ECU to stop all fuel injection while cranking).
  3. Crank in 5-10 second intervals, waiting the same amount of time between each to let the starter cool down.
  4. Repeat this 10 times.
  5. Then take your foot off the gas pedal and try to start normally.
  6. If it won't start, repeat the series of cranking with the gas pedal to the floor.

If it still won't start, do a search on the forums for deflooding DIYs, and pick ONE of the other methods to try at a time. Don't mix methods, that can cause it's own problems.

How Do I Shut Off an RX-8? — Comment éteindre correctement​

This somewhat ridiculous question keeps popping up recently. Other than the obvious "turn the key counter clockwise and remove", there is literally nothing special that you have to do. You will find people that insist that I am wrong in making this statement, but no, it is just that they are taking one symptom and extrapolating preventative measures even further off base than they already were. For example, you will find people that swear by reving the engine to 4,000rpm in neutral and cutting the key out there, with the revs up. They are doing this under the assumption that the faster spinning rotors will help sweep excess fuel out of the rotor housing, to prevent a flood. The problem with this idea is already explained in the Flooding section above. If your engine is already warm, there is no excess fuel being dumped in! (Except perhaps the fuel needed to rev to 4,000rpm). Shutting it off at 4,000rpm is no different in terms of fuel than shutting it off at 750rpm. If your engine is currently cold, then this could only POSSIBLY have an impact if your ignition or starter or battery is failing, in which case 'yes', it might help prevent a flood. But a flood is a symptom of another issue anyway, and only happens on START, not on SHUTDOWN.

Weak Starter — Le démarreur faible (2004-2005)​

On 2004 and early 2005 models, the starter was pretty weak. Mid 2005, Mazda upgraded the starter that they use, and it works pretty well, and lasts quite a while. The 2004 and some 2005 starter upgrades WERE free, but the owner had to do something about it with the dealer. It was NOT a recall. So if you have a 2004 or 2005, it is entirely possible that you still have the original, and very weak, starter.

The starter is an electric motor that accepts 12v power from the battery to power it, and a gear that engages the flywheel to spin the engine when the engine isn't running under it's own power.

If the starter can't spin the engine fast enough, there will be starting problems. The faster a starter can spin the engine, the more immediate the engine fire-up will be. Starters, like any other electric motor, slow down over time and will eventually wear out.

The starter is easily reached under the car (picture), and replacement is very simple to DIY (DIY Starter Change/Swap for Dummies).