[HO455]

Sometimes the simplest things take too much time to deal with. For instance fuel caps. The fuel cap that came with the WMB was a pretty well scratched up chrome unit. I replaced it with a nice locking aftermarket unit. Fast forward to today. I fixed the fuel pickup and that seemed to help the fuel leak, but I could still smell fuel after taking right turns at speed with more than 2/3 tank of gas. I couldn't really find any leaks at the cap but it didn't really fit very tight. To prove the theory I filled the tank to about 3/4's andI swapped the new cap with the old one (which fits tighter). After a couple of test turns with no fuel smell I knew had found the the source of the smell. So the next morning headed across town and about 8 miles later the truck wouldn't idle anymore. The only way I could keep it running was by working the throttle. Nothing seemed wrong under the hood. All the vacuum hoses were hooked up, fuel pressure was fine, the choke wasn't closed. I turned the idle up but it seemed to be surging slightly. I then remembered I had swapped the cap the night before. I grabbed the cap and turned it and heard a big whooshing sound. The engine idle speed jumped up. I turned the idle back down and everything was back to normal. It seems that the old cap is nonvented. The fuel fill isn't in the best condition and it may not allowed the nonvented cap to seal. (Photo 1 is how it is now). When it was in the shop I did some work on the fill and I think that may have allowed the old cap to seal properly when I reinstalled it.
The new cap has a questionable set up to pull the cap's seal down against the fill. The red arrow points to a thin tab that wants to grab the fill but it is too flexible to pull the seal down and it just bends. The green arrow points to a much more robust tab that is too far away to allow the cap to be pulled down and seal.I ended up removing the thin plate, pounding the thick plate flat and grinding the tabs shorter. But that it made it too tight to turn, so I had to give the tabs some angle in order to get it to work.