I scored on the free DW300 from Hox ( thanks again ! ) and am planning to run the DeatschWerks hardwire kit.

From their wiring instruction, seems pretty straight forward but hopefully I can confirm it here with you guys.
Chassis ground, battery power are easy. Then on my 93, the blue-red wire comes in from the COR is the 12v signal / trigger wire. COR has violet wire coming in from ST Sign fuse / main relay.




I assume to properly bypass fuel pump relay, we need to (1) snip the violet wire from ST Sign fuse where the blue cut mark is before COR but after the split to ECU, and reroute / extend that wire to the new DW fuel pump relay as "harness side lead".
Then (2) snip the the blue-red signal wire coming from fuel pump connector to COR where the yellow cut mark is and connect it to the new DW fuel pump relay as "power to pump".

What I'm not sure on is if I need to do anything with that green wire going from COR to AFM. I assume no, as COR is no longer controlling fuel, so any communication between COR and AFM is just redundant noise.

 

That DW hardwire kit is suuuuuuper cheesy for the price. China relay with a cheap plug and some wires that they have laid out to not follow the colors vs. purpose that you'd expect.

Easily duplicated on your own with not-stupid wire colors for about $10.


2/10 would not buy again.

 

It's just as effective, and somewhat easier, to leave the oem pump relay in place, and use the oem fuel pump wire as the coil driver for the new relay located between the battery and the pump.

This will not decrease the effectiveness of the modification in any way, and it saves the user from having to run additional wire and /or Jimmy the oem FP relay socket. Just leave everything under the hood alone, and wire the new relay's in place of where the stock fuel pump would normally be.

 

Thanks for the tip Concealer. Looking on Amazon, I see well reviewed 30/40 amp automotive relays with built in fuse for about $16 for 5 of them including fuse and connector. I'll need to provide my own wires but that's not an issue. I'll go that route instead. The extra relays will be nice for future projects.

Joe, you mean just splice the new relay "inline" behind ( and in conjunction with ) COR by cutting only the 12v signal line ( blue/red ) in my diagram above to use as "harness side lead" for the new relay ?

 

Yes. Forget about messing with the wiring up front. Cut the blue / red wire back at the tank, and hook it up to one side of the coil of the new relay. Ground the other side.

Run battery + to the NO terminal of the new relay, and run the C terminal of the new relay down to the fuel pump. This can all be mounted in the back, right by the tank.

 

However reliable the OEM fuel pump relay is, a 4" piece of 18awg and two spade connectors is likely an order of magnitude more reliable. A single butt connector and some heatshrink is even more reliable still.

 

I think the new relay for fuel makes a lot of sense. I had thought about it but my car is a bit different and the battery is up front and the kill switch next to it.
The 80amp Bosch relays are quite cheap. I bought 2 and keep 1 as a spare. Works like a champ!

https://www.miataturbo.net/race-prep...lay-fix-94026/

 

I also concur with others, had overheating/melting Main Relays until I installed the DW fuel pump hardwire kit. Haven't had a failure since.

 

This is also relevant info for those of us running the drop in RX7 100amp alternator.