Fuel tank pressure with new charcoal canister (1 Viewer)

[truthdetector]

During the first few starts/runs after engine rebuild, I noticed that pressure would build up in the fuel tank.

So I ordered a new Toyota canister from Partsouq for the 105-series based on info I found on other threads. The next couple of starts were no problem so I figured the issue is resolved.

Now, I have started driving the truck around in order to get some initial break-in miles on it.

Today, I did a quick errand and when I got home there was a noise coming from underneath the car. I got down there and decided it was coming from somewhere around the top of the fuel tank. The noise clearly sounded like something was under pressure and air was slowly coming from somewhere. There was no fuel smell.

So I open the fuel cap and all of the pressure was released.

Anyone have any idea what might be causing this?

Every relevant part is new OEM except the fuel tank itself and the hard lines between the tank and the engine bay. Could I have build-up or blockage in the hard line that goes to the canister?

Or, is there a specific inlet on the top of the 105 canister that needs to receive the tank vent vs. the other one that connects to the intake?

I'm a little paranoid of the fuel tank developing a crack.

 

[60 toy ota]

Could I have build-up or blockage in the hard line that goes to the canister?

Yes. And you don't have a crack if you're getting the whoosh out of the fuel tank, you're just prone to it. You'll know it's cracked when the pressure stops building up. Till you get it figured out, open up the gas cap every 1/8th tank or so in order to keep the pressure from building up too much

 

[truthdetector]

Update:

I disconnected the hose from the hard line by the gas tank and ran compressed air through the hard line from the front. Air would flow through, but it seemed to have more resistance than I would have expected.

So I tied a shop towel to the end of the hard line at the back and then sprayed brake kleen in at the front and blasted it through with compressed air. I repeated this 3 or 4 times.

Low and behold, there was a significant amount of what wound up looking like dirt collected on the rag.

A few times checking after running the engine and there isn't significant tank pressure. I'll still keep checking for a while and if I don't get high pressure in the tank again, I'll consider the issue resolved.

 

[FirstToy]

Update:



Low and behold, there was a significant amount of what wound up looking like dirt collected on the rag.

Today, I did a quick errand and when I got home there was a noise coming from underneath the car. I got down there and decided it was coming from somewhere around the top of the fuel tank. The noise clearly sounded like something was under pressure and air was slowly coming from somewhere. There was no fuel smell.

Was there a significant amount of debris when you changed the fuel sock on the pump? Hard to imagine that much debris getting through into the hose.

It sort of sounds like a bad hose-maybe a tiny split or age, and vacuum is sucking in dirt from the top of the tank. Eventually clogging the line and causing your pressure?

 

[truthdetector]

The original sock was not in bad shape at all.

I guess it was just buildup from age. I’m not saying it was dust or dirt, it just looked like it on the rag.

 

[GBinAZ]

Any chance you can post the part number for the 105 canister?

 

[NorthWA]

Funny to read this because I had this exact same experience. Replaced my OEM canister with a 105 series canister and figured my problem was solved. Opened up the gas cap today and got a high pressure release. Seems I have the same problem or blockage.

 

[truthdetector]

Any chance you can post the part number for the 105 canister?

No problem.

Other threads describe this, but there are four things you need to deal with when converting to the 105 canister:

1. The 105 canister mounts differently and has plastic that needs to be cut off if you want it to fit into the 80-series mounting bands. I used an oscillating tool to get the majority of it off and cleaned it up with a flap wheel on the grinder.
2. Even after you remove the extra plastic described above, you will need longer bolts/nuts to clamp the bands closed because the 105 canister is just a bit wider.
3. One of the inlets on the top is a smaller diameter and the tube coming from the intake will not seal. Some people purchased the 105-series tube to remedy this, but I was able to makeshift a "bushing" out of a rubber cap to fill the void. One from this set, obviously, cut the top off the cap to turn it into a sleeve.
4. The outlet on the bottom does not have an extension on it like the 80, so you will need some extra tubing and clamps to make it reach to your tubing that leads to the frame.

Can't get it in US, I assume because there is no 105 in the US, so I got it from Partsouq.

https://partsouq.com/en/search/all?q=77704-60290

 

[GBinAZ]

Thank you !

 

[manofthewoods]

During the first few starts/runs after engine rebuild, I noticed that pressure would build up in the fuel tank.

So I ordered a new Toyota canister from Partsouq for the 105-series based on info I found on other threads. The next couple of starts were no problem so I figured the issue is resolved.

Now, I have started driving the truck around in order to get some initial break-in miles on it.

Today, I did a quick errand and when I got home there was a noise coming from underneath the car. I got down there and decided it was coming from somewhere around the top of the fuel tank. The noise clearly sounded like something was under pressure and air was slowly coming from somewhere. There was no fuel smell.

So I open the fuel cap and all of the pressure was released.

Anyone have any idea what might be causing this?

Every relevant part is new OEM except the fuel tank itself and the hard lines between the tank and the engine bay. Could I have build-up or blockage in the hard line that goes to the canister?

Or, is there a specific inlet on the top of the 105 canister that needs to receive the tank vent vs. the other one that connects to the intake?

I'm a little paranoid of the fuel tank developing a crack.

Thanks for the information/education, I'm learning stuff. FYI, I went the Autozone VC120 route. Pressure when opening the cap completely disappeared.

 

[truthdetector]

Funny to read this because I had this exact same experience. Replaced my OEM canister with a 105 series canister and figured my problem was solved. Opened up the gas cap today and got a high pressure release. Seems I have the same problem or blockage.

Worth a try to do a brake-kleen roto-rooter routine. Costs nothing if you already have an air compressor and a can of brake-kleen.

 

[BILT4ME]

Y'all realize there is a check valve in the system and the brakleen thing is probably cleaning out the varnish on the check valve, allowing it to vent to the canister like it's supposed to.

Don't forget to buy a new Toyota gas cap as well.

 

[truthdetector]

Y'all realize there is a check valve in the system and the brakleen thing is probably cleaning out the varnish on the check valve, allowing it to vent to the canister like it's supposed to.

Don't forget to buy a new Toyota gas cap as well.

I only brake-kleen'ed the hard tube that runs from front to back. Not the actual canister.