There is a leak in my fuel line halfway between the firewall and the main pump.I was hoping that it was the low pressure metallic return line because I know how to fix that, having done it already on a 1986 240 usin clamps and a length of rubber fuel line.

Unfortunately I fear that it is the high pressure line. When the engine and the pumps are running, the drip rate reaches drops per minute and the fuel seems to come from a greenish plasticky line. I thought ,if there is avery small hole, that it could be fixed without shrinking the line too much by running a soldering iron on it to melt the plastic and close the hole.

Before taking any heat to this area, I want to drain all the fuel from the line preferably by gravity, coat it with a soap solution and then run compressed air in it to get the fumes out and see where the hole is (as one does with a inner tube puncture ). I am likely to be working in my driveway which is sloped. Where should I disconnect the high pressure line to drain it. By experience I know that that it may be tricky to do it at the main pump end. Where could I do it at the front end - in the engine compartment with the least risk of damaging anything.?
If my method is not good what do you suggest?
Any advice or comment will be welcomed.