DIY : Draining the gas tank - Methods to empty fuel tank
 

Hello,

When I decided to switch to E85 from RON98, I wanted to completely empty my fuel tank. I tried 3 different methods, here is my feedback.


Important note: be extremely carreful when you deal with gasoline as it is a highly flammable product. Always work on a cold engine and avoid any kind of hotspot and flame. You take your own responsabilities...


1. First method, old school : Siphon the gas out with a hose from the filler neck.
--> Forget about this method. It is simply impossible, whatever is the lengh or the diameter of the hose you want to use, you will never be able to reach the surface of the fuel in the tank.

2. Second method, the hard way : Access the fuel from the top of the tank.
Have a look at the following video. At 1:50 you will see how you can access inside the fuel tank from the top, by removing the fuel pump.
This method will take time, you will mess around with the black sticky sealant, drop fuel in your car, and finally you will not be able to siphon out all the fuel from the tank. Bad idea.
https://www.youtube.com/watch?v=Wc8goq7vXLIhttp://

3. Third method, the official method : easy and fast !
This official method is briefly mentioned in the BRZ Service Manual page PM-33. You can find the PDF document here : http://www.ft86club.com/forums/showthread.php?t=8374

You will need:
- Phillips screwdriver
- 8mm (5/16) outer diameter pipe, 2 inch long or more.
- 8mm (5/16) inner diameter hose, 4 feet long.
- a fuel container
- Laptop with Techstream software


a) - Cold engine, ignition off. Pop up the hood, find the fuel lines that feed the injectors, and disconnect the one visible in the picture below with the screwdriver. Be prepared to capture few drops of fuel with a cloth.

https://i41.servimg.com/u/f41/16/50/82/85/tuto110.jpg


b) - Connect the 5/16 pipe with the fuel line, and connect the pipe to the 5/16 hose. Then insert the hose in the appropriate container. And that's it for the hardware part !

https://i41.servimg.com/u/f41/16/50/82/85/img_2010.jpg


https://i41.servimg.com/u/f41/16/50/82/85/img_2011.jpg


c) - Now on the software part, start Techstream, plug the cable in OBD port and put ignition ON (DO NOT start engine). When ignition is ON, the fuel pump will run during few seconds only, so a small amount of gasoline will flow in the container via the hose you just installed.
The goal of the procedure is to take control of the fuel pump with techstream, to turn the pump ON and pump out all the gas from the tank into the container. Easy.


d) - In Techstream, click on "Connect to Vehicle"

https://i41.servimg.com/u/f41/16/50/82/85/tuto210.jpg


e) - Then click "NEXT" to confirm the connection

https://i41.servimg.com/u/f41/16/50/82/85/tuto310.jpg


f) - On the "All ECU" page, select the "Engine" ECU, and click onto the green arrow to continue.

https://i41.servimg.com/u/f41/16/50/82/85/tuto410.jpg


g) - Click on "Active Test" to open the test list and select "Control the Fuel Pump / Speed" and press "OK" to continue.

https://i41.servimg.com/u/f41/16/50/82/85/tuto510.jpg


h) - Start the fuel pump by clicking on the appropriate arrow, the fuel will flow down into your container. The pressure is not so high so that it is safe (watch out for leakage anyway) and the flow is quite decent so that you will empty the tank quickly. The flow will decrease as the amount of fuel is minimum in the tank. Let the pump run until no fuel at all is flowing from the hose. Then simply turn of the fuel pump clicking on the second arrow. DONE.

https://i41.servimg.com/u/f41/16/50/82/85/tuto610.jpg


i) - Exit Techstream and turn ignition OFF. Plug back and secure the fuel line to feed the injector.

https://i41.servimg.com/u/f41/16/50/82/85/710.jpg


By doing this way, I really believe only few traces of fuel are left in the tank.


I'll be glad if this DIY is usefull to somebody someday.
Drive safe.
:burnrubber:

I just got a copy of Techstream and going to try this out.
I put 6 gallons of E85 in my BRZ in Orlando and about 5 miles up the road my engine light turned. My Delicious iPhone app then said E70. knew it was bad E85!!! Really pissed off. Have at least 10 gallons in the tank. Hopefully there will be no problem with my fuel filter of injectors sine I only drove 15 miles home
I will let you know how it goes.

This is great. I'm rebuilding my BRZ that I wrecked over a year ago finally and trying to get the old E85 out. I've had Techstream for years on my laptop, only ever used it to change dealer settings like seatbelt chimes and such lol, had no idea the old free version I had was capable of this, but it worked. Thanks!

I went thru the same process and tried all those methods as well. I ended up disconnecting a fuel line and using the fuel pump too. I dont have techstream so I jump 12 volts directly to the pump using the hot wire coming from the pump controller module.

I just drained the fuel by running the car in accessories position with a fuel line attached to the feed. The pump ran, and the fuel eventually stopped after pulling 4.5 gallons out. I assumed the tank was empty, but it was not. I could only fill up 9-9.5 gallons of gas. There is probably 3-4 gallons left in the car. I am assuming the fuel is on the passenger side of the tank. My guess is the siphon didn't work to bring fuel over to the other side.

For disclosure: I have a K24 swap (shouldn't matter); I have eliminated the Fuel Pump ECU (shouldn't matter); I have eliminated one of the fuel lines (shouldn't matter); I shortened the purge line, which is now vented to atmosphere (shouldn't matter); the car was somewhere around half a tank; the car was sitting for 6 months.

You say the fuel pump will only run for a few seconds. I'm guessing this is because the Fuel Pump ECU determines the fuel pump only needs to run for a few seconds to build pressure because the car is not started. I believe the Fuel Pump ECU steps up voltage depending on the algorithm. In my case, the fuel pump just ran constantly up to the moment when fuel stopped flowing after ten minutes or so and 4-5 gallons later, and then I shut things down. When I filled up and put the accessories on, I heard the fuel pump kick on, and it was loud, and I heard fuel flowing, but then I assumed the pump continued to build pressure until the regulator told the fuel pump to stop flowing or to slow down to maintain pressure. I don't know.

The question is why didn't the fuel pump drain the tank entirely? Does the passenger side get pulled via the fuel pump, or does the right side fill the left side using some type of Venturi effect or something?

If you're talking about pump E85, it's actually well within the norm of expected Ethanol Content. Pumps can supply 51-84%

FWIW - My gas station puts out anywhere around E75-82. Rarely, if ever will you get E85 from a nozzle.

Can confirm that a car with the stock engine/fuel system does not keep the fuel pump running for more than a second or two on ignition power. Sounds like something you changed with your swap made what you did possible.

How can I confirm something for a stock car if I modified my car?

I can tell you what I think, and I think the system will keep draining until the pump side is drained; the car can't siphon gas to the other side of the tank most likely. Try it and see.

Funny just drained mine as fuel has been in there 5+ years. That said, I bypassed the fuel pump controller, so it turns on with the ignition. Basically, disconnect the red and green wires from the FP Controller and wire them together (yellow in diagram). I did wire an inertia switch so it'll remove power after a big hit. Turn on key, fuel comes out.

Apologies to necro this thread but how do I bypass the pump relay to keep it on? After extensive searching I've been unable to even find where the pump relay is located.

For those of you in the same challenge. Solution I found was to power the two pins shown below with 12v power from the cig lighter. To get to the plug for the fuel relay you have to pull the interior plastics in the passenger side rear area. A bit of a hassle, but worked like a charm.

Follow this guide at your own risk.

https://i.imgur.com/Vll8ntu.jpg

No need for any of this.

Just move the 30A PDI fuse
Disconnect supply line, it will keep cyling once the ACC (KEY) ON

So no need to bypassed the fuel pump controller so it turns on with the ignition?


And no need for the techstream software? It's expensive!

How much gas did you have?


Thanks!

Correct.
Do exactly as I instructed above...it takes a little longer because it cycles the power every couple seconds but with a 13 gallon tank...it's not that big of a deal to wait a little longer.
Not sure why it matters how much I had in the tank but I had my tank full...

I did not have to drain all of it, just enough to relieve the pressure off the tank so that when the cover is removed, it does not leak out of the top.