Fuel Tank Pressure

[vandamja 6]

I have a 1967 1067 that I use to mow about 1.5 acres with. I have had the tractor for four years and have been using it this entire time.

The last few times that I have mowed the engine has started to run a little bit rough after about an hour of mowing. The last time it did this I stopped the tractor, shut off the engine and started to unscrew the gas cap. There was so much pressure in the tank it literally blew the cap about 12 inches in the air.

I am guessing that the gas cap should be venting this pressure, and for some reason has started to not do so, but I thought I would see if anyone else has had this happen. The other item of note is that the tractors hood does just barely come in contact with the top of the cap. This has been the case the entire time that I have owned it, but I never had the pressurization issue.

Thanks in advance for any help you can give.

[rickv1957 75]

:thumbs: Sounds like your cap is not venting,repair or replace,Rick

[Roger from southern Iowa 1]

I agree with Rick.

:thumbs:

[W9JAB 156]

Rick nailed it!

[Save Old Iron 1,571]

If there is a replacement cap on the tank, some caps have a vent mechanism that allows air into the tank (allows air in to refill void left by consumed fuel) but for environmentally friendly reasons, will not allow pressurized fuel vapor to escape from the tank and pollute dear mother earth.

Unless your tank gets very hot from exposure to the sun or engine heat, I find that much pressure pretty scary.

If its the original cap - check the vent hole as stated above. If its a replacement cap with a one way "valve" in the cap - think about going back to the original design cap.

[jpmcleod 4]

I agree with Rick and Old Iron. I had the same problem and could actually watch the plastic gas tank being sucked in from fuel pressure. Drilled a real small hole on the gas cap, no more problem.