**Help** Checking Fuel Tank for Holding Pressure.

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Jun 29, 2017
Keaau, HI
Problem: P0440 code about two weeks after re-installing gas tank - possible gas smell around vehicle, but not something strong enough to locate (doesn't seem to be in engine bay or at gas cap). Tank does not seem to be pressurizing (no hiss when removing gas cap - which I believe I normally had before at all removals). I did not replace gaskets on tank when reinstalling pump/fillers/evap, I believe these to be most likely culprit of a leak. Also the small soft line from the evap line to the shutoff valve may have kinked, I forgot to take a photo of the barb position for reinstalling. While hooking it up and fighting the tank into place I remember the bend looking a little tighter than when removing - could this be an issue? Could be gas cap but it is only 2 years old and visual inspection looks fine.

Background: I recently dropped my fuel tank and did a about 70% restoration on the tank and the skid (that had rusted through pretty major). The fuel tank itself was not in great shape after getting into it's clean up. A quick bondo/spray job on the shield turned into weeks of cleaning/painting on the tank and shield. The coating used on the tank seems to get rusted underneath even though in many places the factory sprayed it on thick, seems after age/heat/cracking it allows the metal under it to rust. Cruiser is a 2000' in what I would think is in the top 10% for lacking undercarriage surface rust.. looked super clean when I got it 2 years ago. After multiple treatments of rust remover - pressure washing - disc sanding - rinse repeat, I believe I had a pretty clean surface. I sprayed tank with rust restorer and then bed liner and reinstalled without pressure test :-(. I did not find any pits that looked to be deep enough to perforate tank, but I did not do a complete removal of factory coating (though pretty close). Soft fuel lines were replaced to fuel pump.

Is it possible to do a pressure test on tank from evap line coming from tank or will the cutoff valve block back-flow of pressure from a vacuum gun. Do the fuel lines come into play here at all?
I'd like to rule out the small soft hose that goes from hard line to cutoff valve on top of tank, is this visible/reachable from fuel pump service port - for those of you that opened it?
The FSM says you can add pressure at Evap service port & pinch off a line at the charcoal can and check pressure release at the gas cap, but will it hold pressure enough to check that way?
Part numbers for gas tank gaskets?
How do you test purge solenoid?
Any other help would be great for those of you who have gone into this, I really hope I don't have to drop the tank again - but I'm guessing it is the gaskets.
Thanks Mudders..
Last edited:
If original gasket, almost certain that is a contributing issue.

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