Anyone pressure test a fuel tank before? For P0440 troubleshooting

[fourfive]

As part of troubleshooting my Evap system to figure out where my P0440 code is coming from, the FSM states to check the "airtightness" of the fuel tank by adding .58psi to the fuel tank through the Evap line hose (after unplugging it from the charcoal canister) to see if the fuel tank can hold .58psi for 1 minute. I don't have access to compressed air but would one of those portable air compressors used to inflate tires work for this?

So far my charcoal canister & VSV for pressure switching valve (located on the charcoal canister...at least for 2001-2002) passed all the pressure, vacuum, & voltage tests recommended by the FSM.

 

[fourfive]

Was just thinking that a portable air compressor wouldn't be the best option since my 4runner would have to be running for the air compressor to work.

Also forgot that my brother in law has an air compressor so will see how testing the fuel tank pressure will work next weekend.

 

[pauldub]

An air mattress pump would probably be better. You only need 1/2 psi. Somehow you'll need a valve to close it off so you can see if it holds the pressure. I guess you'll need a low pressure gauge too.

 

[LittleCaesar]

That isn't very much air pressure. I have a digital gauge that works in 1/2 increments.

I know through the years on the forum, though I haven't seen any lately, that with 2002s and the 440 code, it usually was the canister that needed replacement.

Keep us abreast.

 

[fourfive]

An air mattress pump would probably be better. You only need 1/2 psi. Somehow you'll need a valve to close it off so you can see if it holds the pressure. I guess you'll need a low pressure gauge too.

I was thinking of using a mattress or bike tire pump...guess it wouldn't take too many pumps to fill the tank to .58psi.

 

[fourfive]

That isn't very much air pressure. I have a digital gauge that works in 1/2 increments.

I know through the years on the forum, though I haven't seen any lately, that with 2002s and the 440 code, it usually was the canister that needed replacement.

Keep us abreast.

I was hoping my canister would test bad since that would be easier then messing with the gas tank but my charcoal canister passed all the tests that the FSM suggested.

If my gas tank fails the pressure test, that would mean my overfill check valve located on top of the tank would need changing. Will definitely follow up with my findings.

Anyone know where to buy an air pressure regulator that has 1/2 psi increments? Checked on amazon and didn't see anything that went that low.

 

[stir_fry_boy]

Did you try the soapy water trick for the top of the tank?

 

[LittleCaesar]

Here you go. Not exactly like mine but close. The nice ones (found in paint shops and the like) go for $800+ easy:
https://www.amazon.com/Max-Value-Ha..._43?ie=UTF8&psc=1&refRID=TQAAT5Y3AC0Y43VJKGEC

 

[TheDurk]

If I had to do it, I'd try finding a way to adapt my radiator pressure tester. The connection would not be that hard. The gauge is a little high range for 1/2 psi, but I think you could almost go by feel.

 

[fourfive]

Did you try the soapy water trick for the top of the tank?

Not yet because I'm trying to figure out how to pressurize the tank first to see if there is an actual issue. But in the event i have to lower the gas tank I will be doing the soapy water test to check for leaks.

If I had to do it, I'd try finding a way to adapt my radiator pressure tester. The connection would not be that hard. The gauge is a little high range for 1/2 psi, but I think you could almost go by feel.

I initially tried using my mityvac hand pump that i use for brake bleeding but after pumping for a few minutes with no change in the pressure gauge thought that maybe my dinky little hand pump my not be "strong" enough to pressurize my gas tank to .58psi. Either that or maybe it means that my tank actually has a leak somewhere since I couldn't build any pressure when using my hand pump?