Hi!
The check engine light won't stay off, is on continuously (no
flashing).

4x4 Chevrolet Blazer '96, regularlly rustproofed.

The fuel line developped a leak a foot in front of the rear wheel, on
top of the frame (about the only spot where rustproofing didn't seem
to reach.

I removed the drive shaft, then the tank (and  broke the darn fuel
pump spigot because the clip was stuck with dirt, ouch, a 500$+
replacement), then spliced both fuel lines.

I replaced everything back in place, seemingly correctly.

A few days later, the check engine light came on.  Diagnostic code:
Vapor System, small leak (friend of mine has a scanner, I don't
remember the exact numerical code)

I cursed.  I must have mis-installed some line.

I removed the driveshaft then then the tank again.

I checked
- the sensor
- all splices in the fuel and vent lines
- the gasket of the fuel pump
- tank filler neck  hose and filler cap
- I plugged and pressurized the tank, checked it for leaks: no leaks
whatsoever
- I replaced a piece of vent tube that was slightly rusted.

Everything I could see or think of is fine and dandy.

The darn check engine light keeps coming up with the same code.

Anyone has any ideas about it?