[Diy_efi] fuel tank fittings

[wdsmith]

I'm a bit new to this list but plastic welding and I go back a long, 
long time.
Like a lot of other things, it can be done but I haven't found it quite 
as easy as the infomercials make it look.
I don't want to discourage you but to make you aware that higher 
expectations have farther to fall.

That said, there are two basic ways to repair-weld plastic. Both require 
heat and good heat control.

One sold by Harbor Freight (and many others)  is a hot air torch.  It 
requires a supply of low pressure (around 3 psi I think) supply of 
compressed air which passes through a heating element before exiting  at 
the nozzle.  These work OK after you get the hang of it. It has limited 
heat output so initial heating is rather slow but once you get a 
"puddle" started it is not so bad. You will need a backup or the weld 
bead area will sink in the HAZ.  Material composition is important. The 
best source of filler rod is strips cut from the material you are 
joining.  The process is very similar to O/A welding aluminum without 
the flux.  The parent material must be clean and well-fitted. There is 
little visual clue to the temp of the parent material.

On a side note, I have actually used a small O/A torch to weld 
polyethylene before I bought a hot air torch. It works but you do need 
to give it your full attention.

The second method is really not much more than a small soldering iron 
with a special tip. The special tip is made of brass. It has a flat 
bottom surface shaped much like an old "sad iron."  There is a funneled 
hole on the top side which allows you to feed filler rod through the 
tip.  This type works too and, in some respects, is easier to come to 
terms with.  I have two minor complaints; (1) You are limited to 
manufactured filler material (2) The wattage is a bit low for my liking.

Now, if you have read between the lines, you are probably wondering why 
you can't just grab an old soldering iron 9or a cheap new one) and get busy?

I can't think of any reason.

I also cannot think of any reason you can't experiment on some scrap and 
later modify or make a tip to your own satisfaction.

So, as somebody once said, Give 'em hell, Herbie!  Go get your feet wet 
before spending any substantial money.

Good luck.
wds







Clair Davis wrote:
> Anyway, I would rather buy a plastic welding kit than use that money to buy
> extra plastic tanks if possible.  Of course the plastic welding kit is about
> the same money as a new steel tank that I could weld the appropriate lock
> ring in to.  I already have a MIG in the garage.  Not that I would mind
> justifying the purchase of a new tool, but I've got to be mindful of funds
> at this point.
>