Lotus Seven S2 Fuel Tank

[TEM]

Does anyone know what's at the end of the fuel tank pickup line?  My tube is plugged but don't know if there is a screen at the end or just an open pipe.

 

I'm trying to clean out the tank.  The 1970's fuel has been drained but there is a ton of stuff in there.  It sounds like a large bean bag sliding around when I tilt the tank side to side.  a flashlight in the filler reveals a large pile of black stuff sliding around on the residual fuel.  I'm not sure how to get all this out when the filler neck sits about an inch and a half into the tank.  There is a small hole in the filler neck but all this junk is not going to fit through it.  Yet another fun (and filthy) Lotus project.

[IamScotticus]

is there enough hole to get a small wet vac hose in?

Assuming the volatile fumes are gone, I think repeated water suctions could get it out.

[TEM]

This is the fuel line connection so no way to connect a vac line to it, or at least not easily.  Strange thing is that I can push a wire through the line into the tank (I think) but I can not blow through the line.  It's like there is a check valve in there.

[TEM]

I cleaned a staggering amount of crap out of the tank.

[fastg]

Wow, that is a staggering amount of crap, good job that will save you from problems down the road.

 

Graham

[TEM]

And it's all nonferrous so I have no idea what it is.  It clogged up my large funnel like mud.  The color wasn't brown or black but a very burgundy red.

 

[theDreamer]

My guess would be the remains of fuel cell like foam to keep fuel from sloshing about. You say the gas was from the seventies? Even quality bladder foams don’t last much more than 10-15 years.

[7Westfield]

32 minutes ago, theDreamer said:

My guess would be the remains of fuel cell like foam to keep fuel from sloshing about. You say the gas was from the seventies? Even quality bladder foams don’t last much more than 10-15 years.

 

probably right on the foam   when I bought my supervee, the foam was all in the bottom of the bladder--2" of really nasty chocolate pudding

[MV8]

FOR STEEL TANK ONLY, I'd use a lot of lye and water to sit, then flush, then strong phosphorous if there is rust. Muriatic would do both at the same time but very strong, nasty stuff that can burn and blind you. It's good there is a stand pipe in the neck to help prevent overfill/provide expansion space. Usually, there is a small hole in the side of the pipe just inside the top of the tank but there may not be on these.

You can make a finger strainer to supplement the filter(s). Use galvanized or copper mesh (hardware cloth if you can find it small enough) to make it easier to solder the edges. Roll it 3/4 od x 3 inch and solder the end and most of the side seam, then squeeze the end down to the pickup tube od to solder or hose clamp on with an inch hanging off the end. Stainless can be soldered but it takes treatment with an acid for the solder will wet.

Edited December 3, 2023 by MV8

[7Westfield]

If it's an aluminum tank, be very careful with lye, it will attack the aluminum

 

Edited December 3, 2023 by 7Westfield

[TEM]

This is the original 1963 fuel tank.  I don't think there was any foam or bladders installed.  I have never seen any in my other Lotus' either.

[MV8]

The foam is something people add for racing instead of a custom tank with baffles or other methods to ensure the fuel pump pickup tube stays submerged in fuel when cornering.

 

 

[TEM]

Not sure how you would get foam and a bladder in the tank without cutting it open.

 

There is a stand pipe in the tank as you mentioned including the small hole.  The stand pipe is great to prevent overflowing the tank but creates a real pain when trying to get junk out of the tank or all the nuts and bolt I dropped in to aid in cleaning.  My arms hurt from all the up and down shaking needed to hop all the stuff over the pipe lip.

[MV8]

The foam is soft when new, and can be squeezed in. It doesn't have to be one piece of foam. I am not a fan of foam in the tank. Use a magnet duct taped around a stick or ruler to get the hardware out. If you don't have a small pressure washer, consider taking the tank to the car wash after soaking for a day to soften things up. Radiator repair shops had tanks they would also use for fuel tank cleaning but I think they are all gone now.

 

 

[TEM]

Yeah, I had my old tanks cleaned at a radiator shop many years ago but can't find any here in Toledo.  I'm sure there are shops in the Detroit area but I have been successful in the past with self cleaning.  so, I'll give this one a go and see where it takes me.

 

But I still don't know what's at the end of the pickup pipe and why I can't blow through it.  A wire down the pipe hits something hard.  It maybe the bottom of the tank but I don't have a mirror small enough to get through the filler neck.

[toldfield]

My steel tank, 1982 S-3, was a mess.  The SoCal dealer ordered me a new aluminum tank and did not charge me shipping as they had it put in container with a larger order.

[MV8]

You could fill the tank with a sufficient amount of some acid (like drain cleaner), position the tank so the fuel pipe inlet (inside) and outlet are both below the acid level inside, just above a plastic basin where it won't splash when it becomes unclogged, and let it sit a few days, waiting to see if it will leak out (desired result). Wash it out, then use a small air compressor and rubber tip nozzle to blow into the outlet pipe and wash again.

 

The pipe can be replaced or a new fitting added to the bottom by someone who has experience brazing and welding on used fuel tanks (I do).

 

Here is a fellow building a new tank for an S4 (starts around 5:50. Hard to find any pics of any steel tanks).

 

Edited December 5, 2023 by MV8

[SENC]

@TEM - you may be already aware, but borescope cameras have become quite good and quite cheap.  I bought one that connects to my phone a year or so ago for around $40 as I recall, and have used it numerous times since on car and home (in-wall) projects.  

[MV8]

There are many names for the borescopes, endiscopes, etc. Make sure the focal length is at least a couple inches at a minimum. Some are made for a shorter length to where you can't see anything in focus unless it is extremely close to the lens.

[TEM]

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.