Gas tank sending unit??


Junior Member
On my gas tank sending unit there are three fittings on top. two of them go to my fuel pump and the last one just has a little piece of rubber gas line on it. I think that the last one must have gone to the evaporator cannister at some time. It is long gone now.
Can I just block this off? I don't want to get water or anything im my tank. My truck has a 80 cab on it.
1978 Chev 3/4

Chuck Smith

2000 Club Member
You can't block it off. It is the only vent for the fuel tank. You can extend it further if you want, with a longer hose. On the HD Emissions models, and pre-smog trucks, that is the same vent set up they used. In the end of the hose, you put a vent cap. The same type that is used on your front and rear axle vent hoses, and transfer case vent hose. It is a plastic fitting, with a loose cap on it.

You can see one here: