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Overheard a fleet manager say he checks the fuel cap seal on every PM

He said a bad seal can cause a vacuum leak that messes with the fuel system, not just spill fuel. I started checking them with a bit of grease on the gasket to see the contact pattern. Anyone have a better way to test them without the fancy smoke machine?
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2 Comments
rosep87
rosep871mo ago
Ever actually had a CEL from a bad cap on a modern truck?
2
blake_cooper
Huh. I mean, I guess a bad seal could cause some weirdness, but a full-on vacuum leak from a fuel cap? Feels like one of those things that sounds real important but in practice probably just means a check engine light that goes away when you tighten it.
1