Just wondering, why is there a negative pressure in the fuel tank? I hear air rush in as I remove the fuel cap. I thought there was something wrong with the vent in the cap, so I washed it in soapy water, took the valve apart. It looks to be working just as it was designed. So why would they want to have a negative pressure in the fuel tank? No operational problem, except that the tank is slightly sucked in from all these years of a vacuum in the tank. Ideas? Bill B
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2003rubiblue
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- Jun 15, 2013
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I have two thoughts real quick: Is there a breather off the tank somewhere else that is clogged up? The other is it can't be too bad unless you have fuel starvation issues.
reaperman
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- Dec 18, 2011
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I've noticed this on several different bobcats and always wondered why also. My diesel pickup truck is the same way. So I figure it is what it is everything seems to run properly.
Pretty sure you need a new cap if you are getting a vacuum in the tank. New cap wouldn't cost all that much. I have never found a vacuum either on the skidsteer tank or the pickup. On a gas powered car if the cap isn't sealed you get a check engine light but that's a different system. New Dodge trucks don't have a fuel cap I guess.
There is a little spring loaded poppet valve in the cap that lets air in when the vacuum gets to a certain point. I took it all apart and it's all clean and working. I never have a fuel starvation problem, just curious as to why it works that way. Maybe an OSHA thing so there are no fuel fumes? Bill B
