Save Your Main Relay! FM Fuel Pump Rewire Kit (FM Live)

[@chrisschneider7727]

This is always one of the biggest things to update if you're seeking +200hp. Old wiring and thin diameter wire is the main cause of high resistance.

[@FlyinMiataVideo]

Definitely a good preventative upgrade for higher horsepower cars!

[@frogers58]

Yep, know this problem very well. '05 MSM, 285hp. Over a 18mo period went through a dozen relays. At one point had a bag in the glove box with 5 or 6 that I would bend back in place so they made contact. My symptom was that the tach would swing all the way to 9K at key on then hear a relay clicking as I cranked it. Of course it wouldn't start, so I swap the relay. Tried the 40A and 80A versions. Eventually the socket in the relay box melted and warped. Pulled the relay box and cut off all the burned wires. The double crimp on the relay I separated into two circuits and added a second relay. Been a few years and the problem hasn't come back. I think the last time it happened was on a FM Summer Camp tour. I probably ended up with something similar to what Andrew came up with.

[@michaelh.9866]

Thanks, Keith!

[@merlyn2121]

Ooh. Wonder if Miata Mike or Brandon are going to do an install video. If I ever replace my fuel pump I'll be adding one of these.

[@FlyinMiataVideo]

We can add that suggestion to the list! Thanks!

[@merlyn2121]

@@FlyinMiataVideo I don't think people know how valuable your install videos really are.

[@calebburt9632]

My fuel pump relay went out a while back. I ended bypassing it with a little wire and it has been fine ever since

[@FlyinMiataVideo]

Not a great idea, as you want the fuel pump to cut out if the engine stops. Otherwise you've got a very high risk of fire in a collision or if a line breaks.

[@ricepony33]

I’ve had the main relay fail twice on my 94 in short succession. Both resulting in a tow… really made the car feel old.

[@FlyinMiataVideo]

It's a right of passage for owners of older Miatas.

[@MrSprintcat]

First on race day.

[@RobertMeany]

I was wondering if you guys have any experience with ND2 fuel pumps and related electrical? I recently put in a supercharger kit from Fab9, which included upgraded injectors and pump.. While tuning, we're having issues with fuel starvation at high RPMs and I'm wondering if perhaps the stock wiring/relay is not up to the task...

[@FlyinMiataVideo]

Sorry, we don’t. We used factory pumps in our V8 conversions and amazingly they were up to the job. Direct injection engines start acting weird when you get past 25% duty cycle on the injectors, which will happen at high rpm first.

[@brandonlow27]

What wire gauge are you using for the main power wire?

[@FlyinMiataVideo]

The power wire in this kit is 14 awg.

[@mars-lv9xo]

Could this be the reason my 91 engine dies randomly? I’ve gotten towed 3 times now in the last month. Car will drive fine & suddenly the RPM needle will drop to zero. Car will roll to a stop & then wont start again. Really frustrating because I’m always wondering if I can make it to and from home.

[@FlyinMiataVideo]

Possibly. When the main relay fails, it cuts power to the ECU so the car stops running like someone turned off the key. Most other failures have the engine sputtering to a stop. They don't usually come back again, but it's possible letting the relay cool might bring it back. It's certainly worth investigating.

[@starstar5657]

Don't put a spare in the gloves box, replace it and keep the old in the glove box if you must and forget about it. they generally last over 20 years. my current one is still going after 25 years.

[@FlyinMiataVideo]

Something is better than nothing!

[@wesleydotcom]

Should I expect there a parasitic drain on the battery if I install this?

[@FlyinMiataVideo]

Not at all.