Anyone who races a Spec Miata is familiar with the Advanced Autosports adjustable fuel pressure regulator kit. I have had one on my car for years and I’m a big fan. It fits well, works great and is as reliable as a forged-steel hammer.
One of the accessories that you can get is a drain hose so you can empty the tank completely before a race and only put in what you need. That way you’re not carrying any extra weight. However, they want probably what would amount to $100 for it with shipping and I figured I could make one for less that was just as good.
I also wanted it to drain from the rear of the car, right from the regulator so that I wouldn’t have to break into the factory fuel system under the hood. Miatas are really good about not catching on fire, and I wanted things to stay that way.
I had everything I would need in my garage except for the Jiffy Tite fittings I like so much. The unused fitting on the regulator was a AN -6 that used the O-ring boss seal. All I needed was a -6 valved plug and a -6 valved socket. The Jiffy Tite 22106 and 21506J were just the ticket. Summit Racing shipped them to my door for $77.20, so the savings didn’t amount to much, but I like the kit I made better than what I could find online.
I already had the fuel injection hose, which is what drains the fuel into the gas can at the track. I used a factory pinch clamp to fasten it to the Jiffy Tite plug barb. The socket just threads into the regulator. Both are valved so it’s a dry break on both sides.
I just needed to make a jumper to ground the fuel pump terminal in the diagnostics box under the hood. I had the narrow blade terminals, wire shrink wrap and an eyelet to accomplish that.
By attaching the eyelet using the same bolt used to mount the diagnostics box, you can ground the fuel pump connector so it runs when you turn the key to the on position. Connect the drain hose to the plug on the fuel pressure regulator, ground the fuel pump terminal, then turn the key on and fuel pump will run to drain from the regulator into an empty gas can outside the car.
The whole kit took about 20 minutes to make and I did end up saving a little money. Here’s how this little quick-and-dirty project came together in the garage.
Jiffy Tite makes a variety of fittings for fluid handling, with and without valves. For $77.20 delivered to my door, I got two valved fittings that make for a dry break on both sides. That way, there is no fuel spilled when you connect or disconnect the fittings. Jiffy Tite also makes gold anodized fittings if you want to get fancy. I chose not to get fancy.
Using the 215406J Jiffy Tite socket, some fuel injection fuel hose I had on hand and a factory pinch clamp were all it took to make the hose to drain fuel overboard into an empty gas can.
You need to make a jumper wire to ground the fuel pump terminal in the diagnostics box under the hood. This end fits into the diagnostics box, terminal marked F/P on the diagram. You can jump a wire from F/P to the GND terminal, but I wanted a wire that would always be there when I opened the hood, so I ground it to the chassis with an eyelet.
Crimp the eyelet on the end opposite the blade terminal, cover it with shrink wrap and heat it.
Shrink wrap and a butane torch make for a nice finished product.
On the Fuelab pressure regulator used in the Advanced Autosports kit, the unused fitting on the right side is plugged with a -6 O-ring fitting. Remove it and thread in the Jiffy Tite 22106 plug.
By attaching the eyelet using the same bolt used to mount the diagnostics box, you can ground the fuel pump connector so it runs when you turn the key to the on position. Connect the drain hose to the plug on the fuel pressure regulator, ground the fuel pump terminal, then turn the key on and fuel will drain from the regulator into an empty gas can outside the car.