So I spent 7 years doing a ground up build on a 72 fj40. Me and a buddy installed a 350 with tbi and a man-a-fre 27 gallon fuel cell. I kept having issues with a full tank over pressurizing and pushing past the sending unit. He found a thread somewhere that gave us the idea to drill a small vent hole (-1/8") in the fuel cap. Now if I get on a good incline and near full tank this thing pukes fuel bad out the cap. Anyone encountered these issues?
fuel tank pressure- fj40
- Thread starter 40fever
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
Replace the cap with one that doesn't have a hole. Tee off the overflow line and run a length of hose to a location (outside the passenger compartment) that will be above the level of the tank when on an incline. Put an breather or small filter on the end.
What kind of vent lines is the fuel cell equipped with? I would hook those up to the factory vapor separator, and keep the separator hooked up to the charcoal canister. Hard to beat factory setup on the evap stuff...
yep I did the same with smaller diameter vent holes on both my trucks, my 70 series is fine but my 40 series forces fuel out off angle on a full tank. My 70 series used to vacuum the tank causing cavitation problems and the vent hole I drilled in the cap cured that so I did the same to my 40 series that wasn't causing vacuum issues and ended up with the pressurising and overflowing problem. I drilled smaller holes than your 1/8" hole I started with a 1.5mm drill that broke and ended up using a 2mm or 2.5mm drill.