Rotary Engine Flooding

From Rotary Engine Wiki
Jump to: navigation, search

<google uid="C01"></google>

Common Symptoms

  • Vehicle was running fine the last time I parked it, but now it won't start
  • I can hear the engine rotating, but it sounds strange. Also, I smell gasoline.
  • I moved my car from the garage to the street, turned it off and now it won't start.
  • I left my car with a friend and they moved it. Now it won't start.
  • My car has been sitting for a long time and won't start.


Fuel injected rotary powered cars are prone to flooding by nature. It can be as simple as old plugs or ignition wires, to as complex as intermittent EFI computer malfunctions.

The most common problem is not really a defective part or failure, but a "bug" found in the EFI system. If the car is started, allowed to run for only a few minutes, turned off, then attempted to restart later, it will likely flood. Even if everything else on the car is perfect, this problem cannot be explained, or "fixed", just have to learn to avoid the situation. Every time the car is started, must allow to fully warm up before turning. Common story is moving the car from driveway to garage, only running for few seconds, next morning cranks, but not starting.

Mechanical problems such as low compression due to high mileage or dirty/leaking fuel injectors contribute to the problem. Electrical problems such as slow cranking speed due to weak alternator, bad battery/ground, or starter can result in too much fuel being injected, saturating the spark plugs. If an engine has been severely overheated, may be inhaling coolant into cylinders, characterized by white smoke on startup. Higher mileage models may have weak oil seals, causing oil to seep into cylinder while car is sitting, and smoking (blue) when started or held at continuous high rpms for several seconds. Only repair for both is engine replacement or overhaul. On automatic transmission cars, similar symptoms appear when the vacuum modulator diaphragm goes bad, resulting in ATF inhaled into the engine under high vacuum situations.

Rotary Engine Flooding Prevention

Any trip that is too short for the engine to reach normal operating temperature (needle in middle of temperature gauge indicates normal temperature) should follow these steps to prevent flooding of the engine.

  • With the engine already running,
  • Raise the engine speed to 3000 RPM for 10 seconds
  • Return to idle
  • Turn off engine

The above are instructions to prevent flooding as described in your Mazda Owner’s Manual. We have been using a slightly different method that does not require holding engine speed at 3000RPM for an extended period of time. Here are the instructions:

  • With engine already running,
  • Raise the engine speed to 3000RPM
  • Holding the engine speed at 3000RPM, turn the ignition key to the “off” position,
  • While simultaneously depressing the gas pedal all the way down.
  • After the engine has completely wound down, release the gas pedal.


The RX-8 having a rotary engine, floods like any other rotary engine. The RX-8 also seems to have some sort of barometric learning, which can cause flooding with sudden weather changes. For example, we get this in the bay area a lot, one day is 75, then the fog rolls in, and the next is 50's, and we'll get 1-2 RX-8's in on tow trucks.

Unflooding them is a little different than the RX-7's. There is an updated starter, and battery. There is also a relay for the fuel pump in the main fuse box under the hood. You simply pull the relay out, and crank (forever), until it starts. The spark plugs are difficult to reach from the top. They need to be pulled from the bottom.

<google uid="C01"></google>