Kurt Robertson Enterprises
RX-8 Hot start problem is unfortunately an increasingly common fault in the RX8. You are experiencing this problem if you find that after shutting down at a gas station the car will not restart, but starts after a 10 - 45 minute wait.
This IS NOT a normal characteristic of the car, unless the RX8 has over 60-80K miles.
All healthy rotary engines, should start like any other car when hot or cold.
Don't confuse hot start problems with flooding problems. Flooding only occurs when the engine is cold. Flooding and hot start problems are two completely seperate issues.
Generally two conditions cause the hot start problems.
- A engine suffering from low compression.
- A slow crank -starter motor or battery
The only way to determine which of these is affecting your car is by having a compression test performed.
It is important to have a compression test carried out by a rotary specialist, as the testing needs to be interpretted as well as done with rotary engine specific compression testing equipment.
It's also important that this test is carried out first cold, then hot and lastly wet for a comprehensive comparative test. A cold engine will produce better, but misleading results. These rotary compression tests will tell you quite a few things if you know what you are looking at.
According to Mazda, your results should read between 6.9kgf and 8.5kgf at 250rpm. Cranking speed and compression are directly related. Mazda state that any rotary engine needs 180rpm to start. I've found this to not be completely true but it is a good indicator, so anything faster than 180rpm is good, you really need 230rpm - 250rpm.
Just to be clear, in the same way that a slow starter motor won't start a healthy engine, a very fast starter motor (i.e. 280 + rpm) will start an unhealthy engine and so can be used to mask engine problems. If, after you've had a compression test carried out, you find that your starter motor is slow but your engine is healthy, simply fit a faster starter motor or fresh battery. I have seen this scenario work on several occasions so it does occasionally happen!
Unfortunately in 80% + of cases it is low compression that is the problem, not helped by a particulaly slow starter motor on the older cars.
In this instance you have two options:
- You can gamble and fit a fast starter motor and new battery to mask the main issue in hopes that it will start or
- You can opt to have your engine stripped down and rebuilt with new parts giving it a new lease of life.
The first option, a new starter on a dying engine, I don't particulaly think is a fix. It will buy you some time if you are not ready for the expense of an engine rebuild, but ultimately the engine problems will progress to the point where it simply fails. Mazda does however think that it is a fix until you are out of warrantee see "BAND AID ON BROKEN ARM".
Quite frankly it is likely that during failure damage will occurred to the major engine components meaning that the rebuild will be far more costly than it may otherwise have been, when starting first became hard.
Obviously the rebuild option, does require some thinking about due to the cost versus the value of the car. The first step is to find yourself a good reputable independent RX8 specialist who will be able to talk you through the available options before you make any decision.
Why independent? Mazda's policy is not to repair/rebuild a failed engine, but to supposedly fit a new engine, (which is rebuilt) which may or may not have new housings, rotors, etc. but is usually more costly.
I find that costs for this type of work can range from very expensive (where you may well be paying a premium simply for a trade or company name) down to very cheap (likely with corner cutting that will bite you later).
The mid-range generally charge between $5000 and $7000. I come in at the lower end of that bracket and though it is still quite expensive, consider that before I actually start work, I will spend $1800 on a quality engine rebuild kit made by 30 year part distributor and engine builder ATKINS ROTARY -these parts directly relate to the quality and longevity of your rebuild.
If after researching your options you feel you want to use a premium powertrain and are considering having a Authorized Mazda Dealer do a replacement, I would strongly urge you to go to the most reputable source for a better than factory engine by buying a ATKINS ROTARY ENGINE which will have all Atkins parts and completely new rotor housings and then have that engine installed at your dealer , or independent of choice. Atkins currently ships to the lower 48 states.
If you have any additional questions or concerns regarding your RX8 feel free to call me.
Kurt Robertson 503-829-6054