What Miata wiring can I remove from my carbed 347 conversion?
 

Hello folks. This is my first post but I have been a member for a number of months now. I have gained a great amount of knowledge from the numerous posts but I am now in an area of uncertainty. I have contacted Mr. Lee Bohon and received some great information from him on this subject of carbed engine and Miata efi wiring removal. However, I know there are others out there that have also gone the carbureted route and I would like to hear your suggestions before I start cutting things out and then regretting it later.
Lee mentioned about a jumper on the fuel pump relay under the dash but was going to do a little more research on that for me.
Right now there is a mess of wires hanging in an empty engine bay and I am eager to start cutting but at the same time I am apprehensive.

Any advise out there? I'm sure there is from such a learned bunch of gear heads as this forum contains.

Thanks, Wayne.

My car is 1995 with ABS and no "air conditioning". Not required in the frozen tundra of Canada.

I suggest getting the following: a 1995 miata shop manual / schematic and a wiring diagram from a carbed Ford. If that is the way you have decided to go. Read closely the meanings of the schematic symbols and wire colors chart. Trace each circuit that is attached to the Miata ECU to ensure that each circuit will work with out it. you will find several circuits that do depend on the Miata ECU. Again, the symbols will show if the ECU either grounds the circuit or energizes it to make it work. An example is the A/C wiring of my '02. there are three wires that connect to the Miata computer. Now that the ECU is missing I will have to use a relay to ground two of them and energise one of them to make the A/C to work.
It takes some studying the schematics and understanding them.
Good luck, and much success with your project!
Jack

Thanks Jack. Let me see if I understand your post. Wiring is not my strong point.
Study the 1995 wiring dia. to find all circuits that interact with the ECU. Anything unrelated to the operation of a carbed motor (eg. - EFI sensors, engine control sensors, etc.) may be removed from the engine bay. Other circuits related to operation of the Miata that interface with the ECU must be completed using grounding methods or powering methods.
Is that about it?
Did you remove your ECU completely after appropriate wiring fixes?

There are common connection points concealed in the harnesses, and the unwanted wires are sometimes tangled or taped so won't always simply pull out. To do a thorough job you will need to un-tape and pretty much disassemble the harnesses.

Many of the stock pieces on my stripped down carbureted Miata have been eliminated or replaced with different components. Using the factory electrical shop manual supplement I started removing unused wire from the harnesses. I reached a point where it became evident the thing to do was just rewire from scratch and re-use original wires and connectors as appropriate. That also lets you replace the original marginally sized wire that some circuits have. Depending on the extent of modification it may or may not make sense to do the same with your car.

If you are weak on electrical understanding as you say, I'm sorry to say this is not going to be an easy project for you.

Mrduster,
Yes, the entire Mazda ECU and engine harness wiring has been removed.
Al is correct about the extent of the wire removal. I have removed the dash, heater, AC, and blower to allow access to the wiring harness.
There will not be many associated systems to make work without the Miata ECU. Since you are planning to carb your conversion. I suppose that the Fuel pump and AC will not be used, that will certainly simplify things.
You will need the starting, charging and power to the coil. These circuits should be rather easy to combine from Ford to Miata if you have and study the schematics.
Check with some of your friends that know about auto wiring. Good luck with your conversion.
Jack

Simplefying the stock Harness was a breeze, and I did a lot of it without diagrams.

I labeled every connector that went to a part that was deleted and followed the wires back to their roots.

Most cases, things like ABS and the ECU stuff went right back there and was simple to cut away.

I only left about seven or eight wires, for the gauges, switched power to coil, starter and fuel pump....I am sticking to EFI.

It can be done in a day or two,

I even managed to delete the under-hood power distribution panel, for something more compact....

Here is my power distribution block, hidden with the relays...

https://www.v8miata.net/attachment.p...ine=1355883033

Hey guys, thanks for all your great ideas and suggestions. I'm not the sharpest tool in the tool box but I'm also not the dullest. I know when it is time to call in the experts and I will be contacting my good friend and master mechanic Brian. He will be able to sort out this mess of wires and perhaps I may just learn something in the process.
Thanks again, Wayne.

My plan is to use build guide and suggestions on this forum to get it running without removing any wiring. Once car is up and running, I will start cutting wires away that are left "hanging". I will do one at a time to ensure they have no effect on my completed project. This may make some removal more difficult, but I would hate to not be able to get car running and not know why.... thinking it was a wire I removed during the build.