In my troubleshooting to resolve the intermittent failure to start issue, I’ve replaced the ignition switch and bypassed Mazda’s security relay. Neither proved to be the solution, but still worth the try and good things to do regardless.
The next logical step is to look deeper at the circuitry and determine the weak link at a more core level – the Mazda ignition wiring. Here’s the theory. The inadequacy of the Mazda ignition wiring creates a voltage drop that occasionally prevents the starter from activating. This is why I only get a click sound when turning the key, and I have to continually retry until it builds up enough to start. I never experienced the clicking when the car was rotary, but the GM starter draws far more amperage than the Mazda starter and I suspect is exceeding the limits of the wiring.
Although this issue has never left me stranded and is somewhat infrequent… it is still annoying. And more importantly, it is a fault and must therefore be corrected. With all the work I’ve invested recently into the RX-7, I can say that I’ve grown rather weary. The easy way would be to raincheck the fix for another day down the road. However, laziness and procrastination are signs of a man who has yet to understand and consider the value of time. In other words, there will be no excuses, the problem gets addressed now.
The solution: rewire the starter to include a “booster” relay. The concept follows the same exact mechanics as the fuel pump rewire where the original power wire is diverted into a signal wire and the relay translates out a more direct source. Interestingly, Pettit sells this in a pre-made kit form, which is essentially a generic relay with an instructions print out.
Instead of spending $50 on their “kit”, I opted for the Do-It-Yourself route and spent $30 on a Waterproof 40A Hella Relay and Pigtail bundle. This relay is heavy duty and features 2 weatherpack seals.
To start the install, I reunited with familiar friends… the jackstands and the soldering iron (the scissor jack is there only as a backup).
There was an ideal location to mount the relay on the passenger side of the engine near the oil pan and the starter. From this spot, I was able to figure out the routing and cut down the leads on the pigtail harness accordingly.
Luckily, I did not have to extend any of the leads and they were long enough to reach all of the necessary places. I crimped on and soldered the ring terminals, used marine-grade heat shrink as per usual, and finished off the leads with more Painless braiding.
The blue wire had to be connected to the old Mazda ignition wire in the car.
Here is how I wired up the starter booster relay.
- Position 87 to Terminal S
- This is typically a spade connector or another type of connector on the starter solenoid. I transferred over the connector to the position 87 lead on the pigtail, as can be seen in the previous picture.
- Position 86 to Ground
- I grounded to one of the starter mounting bolts with a ring terminal.
- Position 30 to Terminal B
- This is the +12V battery source. I connected to the B pole on the starter with a ring terminal.
- Position 85 to Ignition Switch / Old Starting Wire
- This is the Black/Red Mazda ignition wire that was originally connected into Terminal S on the solenoid, and the root of all the issues. Cut this wire and splice, it is now going to be signaling instead of powering.
- Position 87A – Ignore
- I cut off this lead at the base of the pigtail connector and applied RTV to seal up the exposed strands.
With everything hooked up, I reconnected the battery and started up the car. Since it was getting late by the time I finished, I was only able to try starting the car 2 times, but it worked perfectly on both tries. I am going to continue testing and report back. I am hopeful and confident that this is the remedy all along.