1987Comanche
NAXJA Forum User
- Location
- NC
I replaced the tank in my '90 MJ right after I bought the truck because the OE tank leaked at the seams. Since then I've noticed what seems to be a lot of pressure buildup in the tank. Even when it's cold I'll have a lot of hissing when I open the cap. The tank has 2 rollover valves in the top and I know the vacuum lines aren't kinked. I tried hooking the vacuum pump to the lines and it holds 15" vacuum but that doesn't translate into any type of hissing/sucking noise when I remove the gas cap. I suspect one/both of the vent valves are not working. What else can I do to diagnose this problem??