ADVICE on- Emptying / Cleaning an AE86 Fuel Tank ???

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Does anyone, have any idea how I can clean/empty an AE86 fueltank without taking the fuel tank off, as I have some rubbish stuck in there. Which maybe the cause of the car missing???

A friend told me that I can empty it by jacking it up, and unscrewing a cap from the bottom?? but god knows if that is true???
Can someone please help.

[XJS]

You can make it empty it if you remove that cap, but you can't clean it that way. We've a specialist who do this kind of jobs with old motorcycle fueltanks. First, he fill it a bit with pebbly sand, and shake it for a day on a special shaker machine. Then, fill with cleaning acid, shake, draw, fill, shake, draw cycles repeated. Finally, apply some fuel tank restorer (that some kind of coating which is fuelproof, antirust, whatever) and shake it for a couple of hours to get the material everywhere inside.

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should quite a complicated and long process..