'77 911 Fuel Tank Repair - What's That Donut Inside?

[Avanti]

I just picked up a 77 911S that has been sitting for 18 years. The fuel tank has some rust so I am getting it cleaned or boiled out if possible. I took it to two radiator shops today for repair. One shop recognized the tank right away as a Porsche tank but had never seen the brown plastic donut looking thing inside. He said he had repaired a lot of Porsche tanks but had never seen one of these. He said he couldn't boil the tank because the heat it would damage the donut. If he could do it, a boil out and reline of the tank would cost $575.00. Ouch!

The other shop I went to said the donut was a filter similar to what older Datsun. Z cars had. Due to heat during the boiling process, the donut would have to be removed to boil the tank. But he said it didn't matter because the filter or whatever the donut is probably doesn't work anymore. He said he was going to get a screwdriver to break up the donut, remove it in pieces, boil the tank and reline it, plus weld a small hole. Total repair cost would be $215.00.

And the cheaper shop is in a better neighborhood.

But, what is the donut thing and is it necessary?

Thanks!

[pete3799]

Cleaning a Fuel Tank without damaging Plastic Swirl Pot

[Avanti]

Pete, thank you for the link.

I am very afraid of having the tank coated. Theoretically they are good but the issue is the tank has to be perfectly clean.

I'm going with the access hole.

So I assume the swirl pot is to keep the fuel from sloshing around?

[CountD]

Don't waste your time with this tank. It will be NOTHING but a headache. You trying to save a couple hundred here is not worth it at all. Buy a new tank here at Pelican and be done with it at $400 or so. The fuel system on a CIS 911 is the one of the most important parts of the car in keeping it healthy and reliable. Your tank is smoked. Mine was in a '75 for twenty years and had the same issues. Boiling it is not worth it. Sealing it will only lead to more headaches. Boiling it will not get all the rust out and if not sealed, will only keep rusting. Put the money down now and save yourself from dealing with it in the immediate future.

PS. And the swirl pot is there to keep the engine from fuel starvation when driven hard, especially in corners, etc. The new tank will not have it. But it's better than salvaging an old tank that will be nothing but trouble.

[E Sully]

Wihrl pot is very important in fuel injected cars. Coating is not a good idea.
CIS Gas Tank

[allaircooled]

Originally Posted by CountD

...

PS. And the swirl pot is there to keep the engine from fuel starvation when driven hard, especially in corners, etc. The new tank will not have it. But it's better than salvaging an old tank that will be nothing but trouble.

I bought a new tank from Pelican and it had the swirl pot. Made of metal instead of plastic.

[sugarwood]

Are the replacement tanks considered to have a good fit ?
Any known issues with the replacement tanks?
Do you just leave the tank unpainted?

[allaircooled]

Originally Posted by sugarwood

Are the replacement tanks considered to have a good fit ?
Any known issues with the replacement tanks?
Do you just leave the tank unpainted?

I have heard of some having a problem with the filler neck not lined up correctly. I did not have this problem. I did however, had a problem with the screw in filter on the bottom of the tank. The socket where the filter screws into wasn't centered up perfectly with the hole. So I had to dremel some of the tank to allow the filter to screw in without tearing up the gasket.

I painted my tank with wurth stone guard, but found out the hard way that the stone guard isn't fuel proof so I will have to repaint it at some point.