I can't beleive it, I was getting intermittent Check Engine lights on my '91' XJ. After reading this newsgroup I tried cranking down my gas cap a little more and now no more Check Engine light. The thing I'm wondering is why does the emissions system care if my gas cap isn't completely tight? Is the fuel tank pressurized or something?
-Bill (remove "botizer" to reply via email)
Fumes from the gasoline evaperating in the tank.
JoBo
Yes. There is a pressure sensor in the fuel line to the charcoal cannister. If the vapor pressure is too low it will trigger the check engine light. All modern cars and trucks have sealed gas caps, and have for many years now.
Always check the cap first thing if you get a light and have no code reader handy. It's a relatively common problem.
You may need a new cap assembly if this reoccurs.
John Davies
Better keep looking for the cause of that Check Engine light. A 1991 XJ couldn't care less if you took the gas cap off and threw it away.
Jeep didn't start monitoring the evap system until 1996, when OBD II was implemented.
LOL
I suppose you've seen this sensor, eh?
Sure it does, check out trouble code 31.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT'sbllsht wrote:
The 1991 XJ has no clue if the gas cap is on or off. It has no clue if the evap system is leaking or not. You can post all the trouble codes you want, the fact is, the evap system is not monitored for leaks.
My manual says different. It says to check the hoses and system for leaks when code 31 comes up. That would include the gas cap....
I will believe the book instead off 'bllsht' any time... LOL!
Mike
bllsht wrote:
Your manual is wrong, and so are you.
You were probably watching them pressure test the cap.
Too funny, the book is wrong and the guy who actually fixed the problem by believing the book is wrong and the bull s*it artist is right. LOL!
Mike
bllsht wrote:
Thank heaven. Though that may change in the next couple of years in SE Mich...
Don't believe everything you read in an aftermarket "manual". They are notoriously wrong.
There is no code 31 for a 1991 XJ. No part of the evap/purge system is electronically controlled or monitored.
Believe your "manual" if you like, but facts are facts.
And I'll beleive Mike Romain over any newbie w/the handle bllsht as well.
-Bill (remove "botizer" to reply via email)
The least the anon BS artist should do is hide his adelphia.net origin if he want's to be so anon.
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