Starting Problems - and the Flooding issue.

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Starting Problems - and the Flooding issue.

Post by crabacle » Sun May 09, 2004 10:28 pm

The RX8 (and many other new cars which comply with EURO 4 emissions) can be prone to flooding. The reason for this seems to lie with the need for the catalyser to be warmed quickly to comply with EURO 4 emissions. This means that initially the engine runs very rich increasing the risk of flooding if the engine is not allowed to warm up before switching off.

The manual gives advice on starting which will minimise the chance of problems. The recommended procedure is to depress the clutch; do not touch the accelerator; crank the starter until the engine starts, even if that means cranking the starter for up to 10 seconds. The engine sounds a bit different from a piston engine when starting and can take longer to catch but it’s best to keep going rather than have several attempts.

If this does not work after several attempts then either call Mazda Assist or fully depress the accelerator and crank the engine for 10s (This actually shuts off the fuel to the engine and helps clear fuel from chamber), then try to start as above again. Alternatively removing the fuse to the fuel injection system and cranking the engine should have the same effect.

If this doesn’t work then the plugs may need to be removed to clean them.
Following an episode of flooding the functioning of the cat should be checked by the dealer as it has been known for the unburnt fuel to damage the cat.
In practice problems only seem to happen following a short move from cold e.g. moving car from garage to driveway. If you need to do this then run the engine for a few minutes or go for a run round the block before switching the engine off.

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Post by cool'n'funky » Fri May 09, 2008 12:49 pm

The Flooding Myth
Flooding Myth wrote:"It's really easy to flood an RX8, and they flood all the time."
This is part true, but mostly untrue.

If you start up an RX8, move it 2 feet and then stop the engine, you dramitically increase the chance of flooding the engine (for the reasons described by crabacle above). It's not a certainty though. That said, it is strongly suggested you don't do that.

You don't have to go on a 10 mile run to avoid the problem though (although it might be fun).

How to minimise the chance of flooding
  • 1 - If the temperature gauge is in it's normal position (normally there after ~5 minutes of driving), then it's highly unlikely the engine will flood. So don't worry about it.

    2 - If you need to move the car a short distance when it's cold (it's ok when it's already warm - see point 1), sit there and enjoy the music/engine/exhaust note for a few minutes until the temperature gauge begins to move. Once this has begun to move, it's highly unlikely to flood.

    3 - Follow the shutdown procedure (although generally option 2 is preferred). There is a leaflet provided by Mazda with the newer RX8's that covers this.

    4 - Go for a short drive (couple of miles). Preferably down some twisty country lanes. That should warm both you and the car up. :D
I've personally followed these guidelines for the last 3.5 years, and haven't flooded the engine yet (now touching wood).

If the worst does happen and you flood the engine follow Mazda's guidelines initially (described by crabacle above), and if that doesn't work try druck's solution (above).
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Re: Starting Problems - and the Flooding issue.

Post by warpc0il » Sat Jan 12, 2019 3:15 pm

Note that the R3 has the faster and more powerful starter, so they reduced the burst time to 10 seconds - see attached page from the R3 Owners Manual.

This is all good, as the faster spin will blow the excess fuel away and may explain why some people *think* that the R3 is less likely to flood - which it isn't - it may just be able to self-clear a minor flood without any abnormal driver action. The same applies to S1s fitted with R3 or equivalent aftermarket starters.

All RX8s built after 2006, or earlier cars that have had the PCM updated, have a shut-down strategy that can help recover from minor flooding and certainly helps with reducing wear and starting in general. When the ignition is switched off and the engine is still turning, the PCM instructs the OMP to give an extra squirt of oil into the housings. This provides a coat of oil to protect the surfaces while parked-up and assist in sealing during the following restart. This is even more reason to NEVER REV THE ENGINE WHEN YOU SWITCH OFF - despite what some idiot dealers may tell you in their youtube videos [-X Revving the engine as you switch off the ignition just wipes and blows away that nice oil coating the PCM has added, making restarts harder and increasing wear.

For those tempted to just walk away and leave a flooded engine to sort itself out - as you can with (most) piston engines, this doesn't work with a rotary, side there's nowhere for the fuel to drain away. Unfortunately, the plugs don't dry at all when just left and the trailing plug could just be sitting in liquid, given the recess with a tiny hole.

For a major flood, removing the plugs not only lets the liquid fuel blow out of the plug holes but also removes the compression resistance so the engine can spin much faster on the starter. It also gives you the opportunity to dry the plugs over a gas flame (usual safety advice applies)

For both the Series 1 and the R3, when trying to actually start, the PCM initially only fires the trailing plugs to avoid kick-back against the starter. at least until the engine has some momentum, then it fires the leading plugs as well.

This is also why a flooded engine takes so long to start, as you have to give it long enough for the leading plugs to join-in too. Short bursts will never work if the trailing plug is wet.
R3 deflood.png
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