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I'm about ready to start wiring. I plan to use the 1990 Miata harness from my donor. However, my harness had some of the engine compartment wires cut, namely some of the wires to the sensors. To replace those wires, I had assumed that I would need to buy what they call a"engine harness", but I don't know for sure. They also have what is called the "injection harness". I don't know for sure which one I need. May-be I need both. I was told that the sensor wires were part of the injection harness and the engine harness was the wires to the starter, alternator, etc. Does anyone here know. Electrical is not my strong suite, so any help is appreciated. Also, I'm using the stock ecu as well as the stock light, turn signal and wiper switch.

I pulled these photos off of eBay. From what I recall, the injector harness actually has two harnesses taped together. The top photo is of the complete assembly.

One is for the fuel injectors as shown in the bottom photo. Looking at the assembly photo, it has four connectors that plug into each injector (the four smaller grey ones on the left and bottom left), two connectors that plug into the main harness (the black/yellow one in the upper middle and the green one on the right) and a ground connector (upper right - which seems to be missing so don't buy this harness!).

The second is for the ignition coils. It has two connectors which plug into the coil pack (the two black/orange in the bottom right) and one connector that plugs into the main harness (the grey/orange one in the lower middle).

I might be off with what goes with what, but if you have all of those connectors then your missing connectors are on the main harness.

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Steve

Thanks. It looks like my problem might be with the main harness.

Have you got a factory wiring diagram(s)? Of not, get one! I'm sure they are somewhere out there in cyberspace. Should be easy enough to tell what function the cuts were made by checking the color of the wires that were cut and their relative location. My wiring for the RX7 was spread out across 25 or more pages broken down by function. Each opposite page showed the connector location for that diagram. Pretty sure the Miata should be somewhat similar.

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Chuck.

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Unless you can find a screaming deal on the harness I'd advise skipping it altogether. I used the factory harness and without exaggeration I can attest that virtually every single wire had to be cut and lengthened or shortened to fit it's new home in the 7. If you have connectors (jus cut wires) I'd invest Ina few rolls of colored wire and go for it as is. If the harness is gone entirely I'd recommend finding at least the plugs so everything hooks up water tight.

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Miata based, custom chassis build in progress. First Drive!!! http://locostusa.com/forums/viewtopic.php?f=35&t=2269&start=375

Use an oem harness and modify the lengths. In your case, to minimize confusion, use a 93 or older harness.

There are step by step instructions on how to properly splice wiring on this site.

Do not cut and splice anything before mounting the parts, routing the old harness and new wiring, and determining how the harness will be supported and protected every 6 inches. Clothes line clips work well to hold wiring in place temporarily. Leave slack in the harness at the ends where equipment connects, especially the engine. Buy bags online of 100 or more 4 and 6 inch black zip ties. Black better resists UV light. Ditto on the use of a spool of multi-wire, multi-color trailer wiring. The colors are not necessary, but will help to keep from splicing into the wrong wire. Small zips can be used to secure a connector where the lock tabs have broken off, which is common on older harnesses.

"ring out" the entire harness before connecting a battery. Sears has cheap meters that have a setting where the unit beeps (ohms/continuity setting) when the leads are touched together. Buy some aligator clips from Radio Shack and make a mini-jumper cable to extend a meter lead the length of the car, in order to be able to test the longest wire in the harness for continuity.

Connect all the grounds in the original harness.

The engine/transmission needs a ground strap to the chassis. You may use a standard lawn and garden cable. Without the strap, the engine will attempt to ground itself through the throttle cable.

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LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
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Collins 241:127x46x12

Thanks. I do have the original harness, which I plan to use, shortening the wires as needed. My problem is that some of the connectors in the engine bay are missing. I plan to aquire those, via either an engine harness or an injector harness.

Thanks for all those tips. That's the kind of info I need.