SL/R129: Check Engine due to bad gas cap?
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Joined: Feb 2006
Posts: 57
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From: New England
1992 500SL, 1990 Jag XJS V-12 Conv't, 1976 Jag XJ12C, another '76 XJ12C!
Check Engine due to bad gas cap?
When I first got my '92 500 SL I had to go through state emissions inspections. Part of the test is a bench check of the gas cap ability to seal properly. While, my cap failed, and later that day my check engine light came on. The inspector was running the car for a few minutes without the cap on. When I went to buy a generic cap at the auto parts store and I mentioned not beleiving that the OEM cap had actually failed, the first thing the guy at the counter said was "Didn't your check engine light come on?" While, sure enough, I changed the cap, reset the code (by disconnecting the battery) and the light has been off since. Has anybody else experienced this? I noticed in this and some other forums people complaining about intermittent and persistent Check Engine lights, some folks spending a ton of money chasing parts and never resolving the problem. They never mentioned changing gas caps though. 
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Joined: Jul 2007
Posts: 11
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When I first got my '92 500 SL I had to go through state emissions inspections. Part of the test is a bench check of the gas cap ability to seal properly. While, my cap failed, and later that day my check engine light came on. The inspector was running the car for a few minutes without the cap on. When I went to buy a generic cap at the auto parts store and I mentioned not beleiving that the OEM cap had actually failed, the first thing the guy at the counter said was "Didn't your check engine light come on?" While, sure enough, I changed the cap, reset the code (by disconnecting the battery) and the light has been off since. Has anybody else experienced this? I noticed in this and some other forums people complaining about intermittent and persistent Check Engine lights, some folks spending a ton of money chasing parts and never resolving the problem. They never mentioned changing gas caps though.
Good luck. rg
