75 Series 1FZ-F Gas tank venting help

[DrRock]

All, I have a 1992 FZJ75 with the 1FZ-F engine and I am experiencing a fuel tank venting issue as indicated by a whoosh when I open the cap (feels like the tank is under vacuum, not pressure). I've replaced the fuel tank cap with a brand new OEM one and the problem persists. Can anyone point me in the direction of a manual with the fuel tank venting diagram so I can diagnose further? I'm hoping it is something simple or maybe the charcoal cannister needs replacement? Any advice or guidance would be greatly appreciated.

Cheers, James

 

[snapdragon]

Use original petrol tank cap.
There is a vent hose under the vehicle next to the tank, it breaks off front the frame and clogs, check that.
Also check all vent hoses to charcoal canisters.

 

[jblueridge]

My old diesel has a bewildering array of tube clusters to accomplish venting and keep fuel in if vehicle is upside down. New replacement tubes came as a pre assembled set.

 

[DrRock]

Thanks guys, I’ll take a look in front of the tank and go from there.

Cheers, James

 

[coldtaco]

On the diesels I have/had there is a little one way valve/filter about half way up the fill tube, looks like a small gas engine fuel filter. Pain to get to. Don’t know if the gas version has this also

 

[davegonz]

Clogged up charcoal canister? Do you still have one?

 

[DrRock]

Clogged up charcoal canister? Do you still have one?

Hello Dave, Yes, engine compartment is like a time capsule, 100% original except for a rebuild on the factory carb. I'm going to take a look once the garage gets above 32F and I get over this fever that was probably caused by working in said garage when it was 8F outside

 

[DenCo40]

Hello Dave, Yes, engine compartment is like a time capsule, 100% original except for a rebuild on the factory carb. I'm going to take a look once the garage gets above 32F and I get over this fever that was probably caused by working in said garage when it was 8F outside

Did you ever figure out why you were getting pressure/vac in your tank? I have a 1FZ GCC (1994 FZJ75 Troopy) that has the same issue. Sometimes my gas cap is difficult to remove even with a new gas cap.

 

[davegonz]

Here's the generic GM fuel vapor canister I retrofitted. I don't have the gas cap pressure issue or gas smell.

Amazon.com: ZONFANT Vapor Canister Compatible With Buick Cadillac Chevy GMC Oldsmobile Pontiac Vehicle 1971-1995 Skylark Skyhawk, DeVille Eldorado, Caprice Camaro, Jimmy S15, Grand Prix LeMans, Replace#911-261 : Automotive

Buy ZONFANT Vapor Canister Compatible With Buick Cadillac Chevy GMC Oldsmobile Pontiac Vehicle 1971-1995 Skylark Skyhawk, DeVille Eldorado, Caprice Camaro, Jimmy S15, Grand Prix LeMans, Replace#911-261: Vapor Canisters - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[javelinadave]

I'm having the same issue and need to figure this out too.

 

[DrRock]

Hello All, I haven't made any progress on this yet except to identify that the 1FZ-F has the same check valve near the fuel filler. Once I can get the truck out I will take this out and inspect. Below is the illustration from the 1FZ manual for reference. Thanks for the tip @coldtaco

 

[javelinadave]

Do you agree it’s PN 9091710020?

 

[DrRock]

Do you agree it’s PN 9091710020?

Yes, agree!

 

[RHINO]

you cant build much vacuum if your gas cap is functioning. heres something to try, disco the vacuum line from the engine and cap the nipple, go for a decent drive and see what happens when you remove the cap again. you SHOULD have a slight pressure.

that check valve is there to keep liquid fuel out of the canister line, specifically when you fill the tank and fuel runs up the neck to shut off the pump handle, thats also why theres a little "catch can" on the neck and other lines connecting. anyway when it fails its entirely possible to pull that fuel into the canister purge system. yours might be stuck open and ALWAYS getting vacuum from the engine, add a cap thats not venting and bam, vacuum in the system.

for folks with pressure in the system its the oposite, the expanding fuel vapors and resulting pressure isnt being drawn through the canister so pressure is allowed to build.

look on the bright side, you know your system is still sealed properly.