I am a new owner of a 1984 Rx-7 with a 12A engine. Could you please help answer a few questions I have about this engine I have not been able to figure out by reading the available books I have. I have read in my repair manual that there is a metering pump that injects oil into the bowl of the carb, but I can not locate this pump on the engine. Can you point me to where to look for this pump? Also where does this pump get its oil from for injecting into the carb? I can't believe it would take oil from the crankcase and inject dirty oil into the carb. I want to find this so I can check if it is working right. Thanks for any help you all can provide me.

 

It is on the right side bottom of the motor towards the front. There are 2 platic tubes that run to the carb. It is run by the oil pump and yes it does put crankcase oil in to the combustion chamber. Check the Haynes manual, it tells you how to check it and how much oil it should put out in a specific amount of time. If you don't like the idea of using a small amount of motor oil in the engine you can disable the pump and run 2-cycle oil with the gas. Do a search on here and you will find a few topics on the subject.

 

Best is to add 8-10oz of 2-cycle (motorcycle) oil or Marvel Mystery Oil to each fillup, then drive without worry of the little OMP quitting without notice and frying your engine. Engine will run smoother, too.

B

 

The oil is drawn off after the filter,so its not "dirty".
But its yet another reason to change your oil often.Over a normal 3000 mile interval,rotaries dont dirty up their oil too badly.Its partly because much of their blowby goes into the next chamber instead of down into the crankcase/oil like on a piston engine.Plus they are just darn simple and compact,theres not a lot of surface area to build up varnish and sludge like in the rocker box and crankcase of a piston engine.
Regular oil changes and fresh air filters will have your 3000 mile oil coming out surprisingly clean.Metering oil pumps are quite reliable and Mazda has yet to change the design since it works quite well.Premixing also works very well,but its another thing to remember,and its something most drivers are not accustomed to.....