How to drain fuel tank

Mustang5L5 · May 31, 2009

I'm getting ready to fire my car up. It hasn't run in 6 years. I've gone through it and changed pretty much every fluid and cleaned up everything i can think of prior to cranking. I've even replaced the fuel lines tank to engine with brand new stuff.

I have yet to prime the pump. Reason being the fuel in the tank is 6 years old. I added stabil, but not sure how it would act if i tried to start it.

I want to drain the tank (half a tank) and add fresh gas. So how do i do it? I beleive the filler neck is an anti-siphon design??? Or is it not??

Or should i fill the tank with fresh gas, mix it up well and then try to start it?

68stang351 · May 31, 2009

There may be a better way, but one of the first things that comes to my mind is taking your fuel line loose, and having a helper turn the key for the pump to prime and let the pump pump it all out into your catch container.

I've done that before on another vehicle, but not on a Mustang, so there may be a better way.

Mustang5L5 · May 31, 2009

The thing is, the pump will only prime for a second and then stop. I'd have to keep cycling the key or jump out something to continuously run the pump. I also don't have a battery for the car yet....so no power

I do have a 190 LPH pump to install, so i was thinking of just biting the bullet, dropping the tank now and changine out the fuel pump and siphoning the tank while I was there.

I really didn't want to do that now though. I just want the old gas out.

Beasty306GT · May 31, 2009

drop the tank..isnt that hard...then u can tottaly drain it and por 15 under the spare tire well... just get a buddy to help drop it using a jack also

tim281 · May 31, 2009

There should be a fuel pump test switch around or in the same connector you do the code checking self test. If you jumper the +12V at this connector to the fuel pump test line, then you will turn on the pump continuously until you pull the jumper wire.
I did this on a Grand National about 1 year ago. I just connected a hose to the shrader fitting on the fuel rail then jumpered the pump test wire. Drained all of the fuel from the tank in a couple minutes. Real ez, just have enough fuel cells to remove the fuel or transfer the fuel into another vehicle once it is full.

LiquidGT · May 31, 2009

Those $2 siphon pumps work faster than you think. The fuel pump self test jumper is a good idea too.

My buddy got an el-cheapo external fuel pump, a length of hose, and some wire with alligator clips... and we drained the tank in his truck like that.

BK_CAULEY · May 31, 2009

water hose and siphon it.

Domindart · May 31, 2009

Ya, take a hose and siphon it, wont sucking it out work?

You dont have to get every drop out, just most of it, I started my car up after a while too and I didnt even worry about the old fuel. It DID run like **** though, so I went to the store and put in new gas and no prob .

As far as priming the engine, its good to do, but I didnt really prime it. Just started the car up.

NotchAbove · May 31, 2009

You can 100% siphon it out. I've done it, and its fast. (There is no real way to get it all out, but you can get more of it.)

ID89GT · Jun 1, 2009

You could also just the relay to keep the pump running.

HISSIN50 · Jun 1, 2009

I would not want to run all the crap in the bottom of the tank through the pump unless you're going to replace it anyhow (and if so, just drop the tank and manually dump the gas).

Mustang5L5 · Jun 1, 2009

SickSix said:
drop the tank..isnt that hard...then u can tottaly drain it and por 15 under the spare tire well... just get a buddy to help drop it using a jack also

That's why i don't want to drop the tank now. I'm out of POR-15. So i'll need to order some up as well as a new tank filler gasket (they always rip) and i was thinking of using POR-15 gas tank sealant inside the tank.

So that's why i just want to drain the fuel now. I have a HUGE project planned just for the fuel tank area.

So you can siphon gas from these cars? I was under the impression they had an anti-siphon filler neck.

I'll do that then.

BK_CAULEY · Jun 1, 2009

just done try iy with a flimsy hose. i promise you you CAN do it. ive siphoned gas out of my cars plenty of times.

strtrcr50 · Jun 1, 2009

tim281 said:
There should be a fuel pump test switch around or in the same connector you do the code checking self test. If you jumper the +12V at this connector to the fuel pump test line, then you will turn on the pump continuously until you pull the jumper wire.
I did this on a Grand National about 1 year ago. I just connected a hose to the shrader fitting on the fuel rail then jumpered the pump test wire. Drained all of the fuel from the tank in a couple minutes. Real ez, just have enough fuel cells to remove the fuel or transfer the fuel into another vehicle once it is full.

This... Jump the fuel pump at the test connector while having a line unhooked and going into a bucket. But IIRC, you don't jumper to 12 v.
On edit, courtesy of JIRichker.

NotchAbove · Jun 1, 2009

If you jumper the relay any junk in the tank is going to run thru your pump and possible clog your pump and sock. Just get a siphon.

Mustang5L5 · Jun 1, 2009

car has no battery yet

I've got a spihon pump...gonna try that first

How to drain fuel tank

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How to drain fuel tank

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