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2001 Miata SE
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571 Posts
Discussion Starter · #1 ·
I need to drain all of the gas in my tank, and I don't want to chip away at the undercoating to get at the drain plug.

I read on here that another way was to wire up the fuel pump to run by itself, or continuously on "key on, engine off," and have the gas drain into a container...

What specifically do I need to bridge(electrically) or "hotwire?"

Thanks.
 

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Easiest way was mentioned above. Take the line off the fuel filter, put it into a container of your choice, turn the key. Done.

Funny trick I learned, but it wasn't funny at the time. If you're MAF, unplug the MAF sensor, unhook the battery, put the key in the ignition and turn it to the on position. It'll continuously pump until the remaining energy in the system is all used up, or until you hook up the MAF sensor or battery again.

I was shocked when it happened to me. I was doing a motor pull, the battery was removed from the car, the fuel lines were unhooked and hanging out. For whatever reason, the key was in the ignition in the on position. I guess I forgot to remove it at the time. I unplugged the MAF sensor and immediately the fuel pump kicked on and stayed on, spewing tons of fuel all over the place, despite the battery being 10 feet away. I plugged the line with my finger, but I couldn't had no idea why, or how, it was pumping, so I didn't know what to do. I grabbed the closest container and shoved it under the line, but a solid gallon, at least, had already spilled out. After I cleaned up the mess and turned the key off, I began experimenting. It had been the combination of the key in and on, the MAF unplugged and the battery disconnected that did it. To this day, I still don't understand how that works. :lol:
 

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2015 WRX STI WRB
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8,417 Posts
another way is taking your cover off the fuel pump assembly and disconnecting the harness plug and hooking up a battery to the two power terminals for the pump itself. connect rubber hose to hard line and viola!
 

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2001 Miata SE
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571 Posts
Discussion Starter · #6 ·
I thought by moving the key to key on engine off, the fuel pump would only prime, like it does normally.

Does it continuously pump because it doesn't see fuel pressure climbing? (when the feed/pressure line is removed)
 

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2000 Impreza RS <Red>
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1,197 Posts
I'm pretty sure "Priming" just means that it turns on to build fuel pressure.

As far as I know, as long as the key is in the ignition position, the fuel pump gets 12V.
 
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