Cleaning a Fuel Tank without damaging Plastic Swirl Pot

[matt gineo]

I just purchase a 1976 Targa that had been sitting for close to twenty years. One of the many issues I had to address was the gunked up fuel tank.
A couple of weeks ago I asked fellow Pelicans for advice about cleaning a very dirty, varnish coated fuel tank. Some very good advice I received was NOT TO HAVE IT BOILED OUT AT A RADIATOR SHOP AS THE CHEMICALS WILL DESTROY THE PLASTIC SWIRL POT! I wasn't able to get much advice about cleaning the tank.

Make 100% certain that there are no gas fumes in the tank before cutting the hole!!
I decided that there was no way it could be cleaned without getting my arm inside the tank to scrape, scrub etc. I cut a 6 inch hole in the top of the tank which allowed me to access the entire interior of the tank. I then fabricated a 6 inch access plate so I can reseal it and get back inside the tank should it have to be cleaned again.
(access plate is sitting on top of the tank in the photo)


This is how I cleaned the tank.

I took the photos before the interior of the tank was completely clean. It is now spotless inside and out.

1. There was approx 1/2" of sludge, varnish goop in bottom of tank. I Removed drain plug with screen filter and placed it in a pot of Simple Green degreaser overnight, The very delicate screen was covered in varnish and I din't want use use an acidic cleaner fearing that it would destroy the screen filter. The next day I removed the drain plug/screen and it was perfectly clean.
2. Flushed the tank with high pressure water to remove any loose dirt, rust, crud etc.
3. Sprayed interior of tank with Gunk Degreaser, let stand for 1 hour then used a plastic putty knife to scrape as much junk as I could off the tank wall.
4. Flushed again with high pressure water.
5. Reached into tank and removed top of plastic swirl pot. The inside of the swirl pot was full of crud. There is no way the pot could have been cleaned out unless
it was opened up. Used wire brush and carb cleaner to clean inside of pot. Then sprayed with high pressure air to remove crud inside of pot.
6. Dumped Simple Green degreaser in the tank sloshed it around for awhile then let it sit overnight. The next day I stuck my arm inside the tank (with the simple green cleaner still in the tank) using a coarse scotchbrite pad I thoroughly scrubbed the entire interior of the tank. Dumped out the simple Green and flushed with high pressure water. By this time the tank was fairly clean.
7. Used a wire brush, scotchbrite pads and sandpaper to remove surface rust then flushed again with water and dried with a heat gun and high pressure air hose.
8. Dumped 2 quarts of Permatex Rust Remover Gel into tank and brushed all interior surfaces, let sit for 24 hours.
9. Flushed with high pressure water and dried with a heat gun and high pressure air hose then wiped interior with Acetone.
10. Dumped in 1/2 quart of OSPHO rust converter to neutralize any small traces of rust that remained in the tank. Sloshed it around to cover all interior surfaces then let it dry overnight. OSPHO converts any rust in the tank to a rock hard surface. I decided not to coat the inside of the tank with epoxy, POR15 etc. because of the horror stories I heard about coatings flaking off and clogging fuel components. Any coatings would also clog the swirl pot.
11. After the OSPHO dried I replaced the top on the Swirl Pot and sprayed the interior of the Tank with PB Blaster to prevent flash rusting until I could reinstall the tank and fill it with gas.

Now onto the next project, Fuel Pump, FD, WUR, Injectors etc!

[Targalid]

Nice job! Hopefully you won't need to use your new access hatch again.

[matt gineo]

Thanks Targalid, I don't think I'll have to use the access plate again because the car won't be sitting in one place too long, I plan on driving it a lot!

[mcaterino]

What fun! Nice, thorough and careful job, and great documentation for folks in the future.

Mike

[porwolf]

Matt, I think you nailed the tank refurbishing issue!!! I looked a many threads here but they did not convinced me that each of the offered solutions really guaranteed a thorough, safe, and lasting solution for gunked-up tanks. You actually were able to work on and inspect the inside during each step and insure effectiveness. Maybe sombody could offer a cover kit like yours for everybody else who faces in the same foulded-up tank predicament.

[matt gineo]

Thanks Powolf, We fabricate and install these access plates on marine diesel fuel tanks. Marine diesel fuel has a tendency to grow algae and all kinds of crud that messes up fuel systems. I never thought about selling the plates to Porsche owners but if anyone wants one send me a PM and I'll be glad to sell them. One thing I didn't mention in my post, pretty common sense but make 100% certain that there are no gas fumes in the tank before cutting the hole!!

[porwolf]

Good point about the gas fumes in the tank! How much are your access plates?

[matt gineo]

Porwolf, the access plates are made of stainless steel and take a while to build. I can sell you one for $90.

[matt gineo]

Just finished welding the patch and installed the stainless steel access plate in case I need to get into the tank again.

[porwolf]

Matt, I think you are a genius. That must be the most efficient and durable tank cleaning solution that I have seen. If my tank acts up that is the way I want to go. I just feel you need a good access to the inside, otherwise you are never sure what the situation is there.

[matt gineo]

Thanks Porwolf, I start putting the fuel system back together tomorrow, new injectors, new fuel accumulator, new fuel pump and relay, rebuilt WUR and Fuel distributor and of course clean fuel tank.
Hopefully I'll be driving the car later this week!

[porwolf]

With you preparations I am sure you will. And, I love your Targa colors!

[matt gineo]

Thanks Porwolf, I'll let you know how I make out.

[RWebb]

re #5 - "Reached into tank and removed top of plastic swirl pot."


Does the top just lift off? Or did you have to release some sort of fasteners?

[matt gineo]

Originally Posted by RWebb

re #5 - "Reached into tank and removed top of plastic swirl pot."


Does the top just lift off? Or did you have to release some sort of fasteners?

There are 3 steel spring clips with barbs that are easily pried off with a small screwdriver.

The inside of the swirl pot was full of crud and there is no way to clean it without removing the top.

[chauser]

I'm working on a 73.5 tank at the moment.
Marine clean has gotten the varnish ar tar out of the tank, but there may be some in swirl pot yet. I've got minor surface rust and am debating if I should open it up as you have, or if there is an alternative rust treatment that does not involve acids, or POR15 treatment.

What is the diameter of your access cover? I'm estimating 4".
No problems pulling top off swirl pot and replacing with 1 hand in tank?
What did you paint exterior with?

Nice job.

[matt gineo]

Charles

The first hole I cut in the tank was 8 inches dia. which was plenty big enough to get my arm in to clean the inside of the tank and to remove the top of the swirl pot. The stainless steel access plate I installed is 6 inches dia. I can't tell you if the inside of your tank is full of crud but mine sure was. After spending lots of time and $$$ replacing most of my CIS components I'm glad I opened it up to clean it out! The way I look at it is, you're screwed unless you have good clean fuel.

I used 3M rubberized spray coating to coat the exterior of my tank. I know it's not original gray but I don't plan to enter my car in any concours competitions.

I chose not to coat the interior of my tank because I was afraid it would eventually come off and clog up my fuel system. After I finished cleaning the inside of the tank I sprayed it with fogging oil to prevent any flash rusting. I installed the tank the next day and immediately filled the tank up with fuel and chevron techron fuel treatment..

Don't use any caustic cleaners, it will melt the plastic swirl pot!

[Grady Clay]

Matt,

Excellent project and thread.
Thank you.

Are there more images of the ‘swirl pot’?

Best,
Grady

[matt gineo]

Originally Posted by Grady Clay

Matt,

Excellent project and thread.
Thank you.

Are there more images of the ‘swirl pot’?

Best,
Grady

Thanks Grady,

I think I have more pics, if not I'll simply remove the access plate and take some more.

Matt

[chauser]

Matt

Thanks for the feedback. It looks like I've got the earlier tank that accepts a full-sized spare. I can fit a ~ 6" hole, but it will be tight.
The marine clean really did a good job removing the varnish and sludge precipitated on the bottom of the tank. I think I will proceed and open it up to deal w/ some minor rust on the top (inside) of the tank, and to check inside the swirl pot.