Fuel Tank Pressure test
 

Anyone know or recommend the pressure to test the fuel tank for leaks?
I failed the Evap/Pressure test for Smog cert in California. I ordered new gaskets for the lower filler neck, evap outlet, fuel pump and sending unit covers. I also am getting new filler neck hose and vent hose. Have replaced the rubber evap and return lines as well. But I would like to pressure the test the tank itself and make sure there are no leaks at the seams or pinholes. Though there is no fuel leakage evident, since I have the tank out I want to be sure. At the same time don't want to over-pressurize it. Any info is appreciated.

Edit - I should have mentioned this on a 1994 4runner 3.0l 4x4.

1/2 psi http://www.bar.ca.gov/80_BARResource...s/LPFETFAQ.pdf (#39)

The "maximum" allowed for manual testing (at least as done with a EVAP testing machine) is 20" of water, which is less than 1 psi. http://www.bar.ca.gov/80_BARResource...2007-08-13.pdf

In other words, you're not going to be using your regular 100psi shop air. (In fact, Evap testers use nitrogen rather than air to reduce the explosion hazard.)

The actual test is a leakage rate, but I think it depends on temperature, so I can't help you there.

If you find out more, let us know.

Good luck!

Thanks for the reply. I appreciate it.

Toyota Tech says 1 psi for a vessel pressure test.
I just flushed the tank, opened everything so all the vapors can escape. Tomorrow I'll blast some air through it to make sure all the vapors are gone, seal it up, set it in a vat of water and weigh it down so it stays submerged, and pressurize it to look for air bubbles leaking. Not an ideal test, but damn if I can find a gauge that will read below 5 psi. So I have a shut off valve ready to inline. Just going to have to be really easy on the air.

Be prepared to add plenty of weight. It takes 144 lbs to hold an 18 gallon tank full of air completely submerged in water.

rather then a pressure test do the opposite and pull a vacuum it is easy to see if it holds .

Any simple vacuum pump most always has a gauge.

If it holds pressure it will also hold a vacuum and a whole lot safer

For all the work i would have just put a new tank in but my labor rates are expensive.

*** I doubt it would take much work to fabricate an adapter to use a coolant pressure tester whole lot safer then hitting your tank with shop air.

Besides you can just watch to see it hold pressure as well.

I like wyoming9's vacuum idea; the simple vacuum pump will never pull enough vacuum to accidentally crush the tank.

But you still have to find the leak (if there is one). Personally, I'd just get an old spray bottle and fill it with soapy water. Pump up the tank with a bicycle pump (gently now; 1 psi is the max you want).

But these are all good ideas; let us know which one works!

is the truck a keeper? if so... since you already have the tank out, just clean it and coat it, no testing.