Ferguson to20 1948 Gas cap Problems

wfcpain · Sep 25, 2017

The engine on my to20 warms the gasoline in the tank and fumes jet out the vent hole on my gas cap. This takes off the paint on the underside of hood and also pools gas on top near cap. I could put a cap on with no vent hole. What are the reasons for the vent hole? Should i put the non vent hole cap on? Will this build up pressure and release when i open tank, causing a mist? Should i rig up a hose to vent cap and run down to ground? Any other Options?

Determined · Sep 25, 2017

A vent serves 2 functions.

1-It allows pressure from expansion to escape.
As you said the heat from the engine is accelerating the warming and expansion of the fuel.
No vent and you could cause the tank to bulge or rupture, the pressure could cause a line to push off, additionally the higher pressure may be too much for the needle and seat in the carb, this can lead to flooding and or external fuel leakage.

2- It allows air into the tank as the fuel level goes down.
Without a vent you will encounter fuel starvation issues.

Is it still a noticeable problem if you only fill the tank to 3/4 full?

wfcpain · Sep 25, 2017

I had a full tank when I noticed. I think it does it at lower levels too at less extent.
You make good points, I'm with you on them.
I see the original cap had no vent. Some owner before me, must of had a problem
with a no-vent cap, maybe he lost it idk , but I'm thinking there was a issue with it like
the ones you mentioned.

It just seems dangerous to have the hood cavity filled with vapor, enough to pool, next to a
hot engine.

My options were no vent cap or a fitting/vent attached hose, but there is no room between the cap and
hood for a fitting and hose setup.

wfcpain · Sep 25, 2017

I supposed with the full tank, it could have force fuel thru the vent hole. I put a new gasket on the cap. When it was warmed up I could see the vapor jet out the vent hole.

Determined · Sep 25, 2017

(quoted from post at 12:29:03 09/25/17) I supposed with the full tank, it could have force fuel thru the vent hole. I put a new gasket on the cap. When it was warmed up I could see the vapor jet out the vent hole.

My thoughts are you are perciving it as a problem observed after the tractor has been warmed up and shut down.

In actual use there is enough air being moved by the fan and motion of the tractor to quickly disperse the vapour long before it has a chance to build up anywhere.

Additionally if the tractor is being worked as the engine draws fuel it should keep the excess venting down to a minimum.

If you are not taking it out and working it hard all day then just keep the tank around half full, should take care of your concern.

Ferguson to20 1948 Gas cap Problems

wfcpain

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Determined

Well-known Member

wfcpain

New User

wfcpain

New User

Determined

Well-known Member

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