hey!
I'm new to the forum, and I own a Honda civic si... so why the RX8? my mother owns one...

so it flooded, I tried all the steps, including the water injection.

I put new plugs in, the trailing and leading. have spark, have fuel... and am currently charging the battery. I know that there has been alot of discussion on this, but to the point. Why does it happen? I understand it has to do with the operating temp. but on the technical side, does it have to do with the closed loop short term fuel trim? the fuel pump dosen't have a return... (BTW I'm an engineering student and work at GM)... could it possibly be from the fuel pressure not being regulated correctly at shut-down... this is truly a headache... Its a beautiful car... but why the mess?

 

Short answer -- liquid gasoline dilutes the oil film on the housing walls and ruins its ability to form a compression seal. And unlike a piston engine, the gas can't just drain away past the rings, into the crankcase. To get a start, you need various combinations of a) removing the excess fuel from the combustion chamber and b) adding oil (or other suitable fluid) to the combustion chamber, and c) lots of cranking rotations at as high an rpm as possible. Search the TSBs for the full shop procedure. People who know more than I, say that a push start will always work eventually, and it makes sense.

Prevention involves making sure the vehicle is up to date with a) appropriate battery, b) improved starter, c) current Flash revision. These largely eliminate the problem but it is still advisable to follow the operating procedure of not shutting down the engine until it warms.

 

If push starting it doesn't work, pull starting it will everytime provided there isn't something seriously wrong with the car.

A rotary is the one engine that will never unflood itself by sitting around. You could flood it and let it sit for a year. It'll still be flooded and still won't start. The reason a rotary is easier to flood has to do with the physical shape of our seals. Specifically the apex seals. In a piston engine the piston rings are flat on the edges. A rotary apex seal however is different. The edge that rides on the rotor housing is not flat. It can't be as due to the way the rotor spins, the seal rocks side to side. This gives is a rounded profile rather than an edge. This is the problem.

A liguid is not compressible. If you get too much fuel into the engine, it will puddle up on the face of the rear most apex seal in the combustion chamber due to the way it moves. However some of this fuel gets under the edge of the rounded profile of the apex seal and has a way of pushing the seal upwards. This lowers compression which makes it harder to start and only compounds the issue. The only way to get it started is to spin the engine faster such as pull starting it. A higher speed exerts more centrifugal force on the apex seals which makes it harder for gas to push them up (or down depending on how you look at it) into their grooves.

If you can't do this, the only thing to do is find a way to get the gas out of the engine. Spinning it faster does do this. Another method which has mixed results is to crank the engien over with the spark plugs out. You'll see a mist of fuel spray out of the plug holes but that's a good thing. Make sure you have a fuel pump fuse pulled! I don't know where it is on this car or how to do it though.

There's yoru answer from one engineer to another!

 

As another engineer...I thought it's because the excess fuel has nowhere to go. It just sits in the bottom of the epitrochoid. With most piston engines, gravity will drain the fuel past the rings into the crankcase.

The same thing happens with the bottom cylinders of radial aircraft engines. The fuel can be drained out of those by pulling the propellor around backwards, since they have valves and cams.

Ken

 

incredible... I guess I need to look into this more. I did get it to crank up. I considered using water because Mazda claims according to their master tech that it is called carbon lock, which would be justified to use water to clean carbon build up, but he said that it is a flooding condition in which the wipers are not sealing do to carbon build up allowing fuel to leak into the opposing combustion chamber. he gave me a small bottle of ATF according to him it was his "combustion cocktail" who knows what else was in it. after cranking it for 6 min, with the fuel choke procedure, I decided what the hay. one 4 once bottle into the intake vacuum port, and 2 spins it fired right up.

Thanks for the responses and I guess I need to do a little more research.

 

Yep you put enough oil in the engine to seal the rotors and allow good compression. Works everytime!!

 

That's true. It just compounds the issue.

 

yea im having the same problem. im gonna go try this. be back later