Lotus Seven S2 Fuel Tank

[SENC]

And no flow the other way, too?

[TEM]

I have not tried pulling air thought it but blowing air in doesn't go.

[Joe Petty]

The Serck gas tank on my 7 was patched, so I opened up the patch to clean out the varnish from the old fuel.  The bottom of the tank had probably 1/8" thick solid layer of varnish that I broke up and scraped out with a putty knife.

The fuel pickup tube is just a plain piece of tubing that drops down maybe 1/2" from the bottom of the tank.

No filter, No one-way valve...  Just as simple as you can imagine!

When I got the tank all back together, I used 2 packs of motorcycle tank cleaner and sealer.

 

Note- My tank was sitting for over 20 years, so de-gassing was not a problem.

 

Be Careful and Good Luck

[MV8]

12 hours ago, TEM said:

I have one a borescopes but the light source is not strong enough and there is not enough control to get it close enough to see the end of the pipe.

 

I don't have to do anything fancy to soak the clog in the outlet pipe.  I just fill the pipe from outside.  Since it's clogged, the fluid just sits there.  No motion in the clog for two days now.

Place a small sample of the goo you already removed in a container, then test with different acids to find one that will visibly react. If your funnel is not higher than the pipe inlet inside the tank, it won't siphon/flow even if you soften the clog. That's why I suggested inside the tank with the entire pipe below the fluid level.

[MV8]

2 hours ago, Joe Petty said:

The Serck gas tank on my 7 was patched, so I opened up the patch to clean out the varnish from the old fuel.  The bottom of the tank had probably 1/8" thick solid layer of varnish that I broke up and scraped out with a putty knife.

The fuel pickup tube is just a plain piece of tubing that drops down maybe 1/2" from the bottom of the tank.

No filter, No one-way valve...  Just as simple as you can imagine!

When I got the tank all back together, I used 2 packs of motorcycle tank cleaner and sealer.

 

Note- My tank was sitting for over 20 years, so de-gassing was not a problem.

 

Be Careful and Good Luck

Is the pipe attached inside the tank or is it only attached where it passes through the tank wall?

[Joe Petty]

Not sure!

I don't recall reattaching the pipe inside the tank.

I only had to touch up the outlet since I soldered a fitting to the pipe on the outlet.

[MV8]

TEM, have you cleaned out the tank bottom yet? The borescopes typically have a button for taking pics and variable brightness thumbwheel. Maybe post some pics of the tank inside and out? Is it like the S4 but shorter in width to hold about 5 gallons?

 

A new pipe can be brazed in if needed by cutting it out with a rotary file and needle nose pliers to pull it out if not attached inside. A new pipe from 5/16 brake tube can be inserted fully to hit the bottom, pulled out a 1/2 inch, then cut and flared while still straight before bending, then brazing or silver solder to the tank wall. If the hole is too big, fit a washer.

 

I'd be tempted to add a 1-1/2 inch length of 2 inch exhaust tubing to the bottom for a g force defying sump and a brake pipe fitting for the outlet.

 

 

[TEM]

Finally got the tank to an acceptable point.  Over 200 flushes with water and lots of nuts and bolts.  I tried a number of acids and cleaning solutions and none did anything to this stuff.  It's not like varnish, that's easy to clean.  This stuff is like sand when dry, very course and grainy, but turns to red mud when wet.  Spent 4 hours of fill, agitate, and dump.There is a baffle in the tank so you have to clean one side then push all the nuts and bolts to the other side and agitate some more.  Every flush was producing about two tablespoons of mud and that was after the big bowl of junk came out.

The pickup tube is also now clear.

One long, dirty, and painful job complete.  Now on to the next problem area.