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What is a failed gas cap functional test?

Tiny
MICHAELPC
  • MEMBER
  • 1987 HONDA CRX
  • 190,000 MILES
I have a 1987 Honda CRX and it wont pass smog. I believe that it is because of a failed gas cap and I was hoping someone could tell me what causes a gas cap to fail a functional test
Tuesday, September 13th, 2011 AT 3:33 AM

13 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
They are designed to vent pressure at a certain point. If they release too soon or late, it will fail.
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Tuesday, September 13th, 2011 AT 3:41 AM
Tiny
MICHAELPC
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  • 7 POSTS
So would buying a new gas cap fix the problem and would my car then pass?
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Tuesday, September 13th, 2011 AT 3:45 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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That I can't answer. If they said the only problem is the cap, it should. However, there could be a leak in the EVAP system. The cap is the cheapest try at this point. If there is still a leak, I recommend having the system fogged to identify where a leak is located.
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Tuesday, September 13th, 2011 AT 3:47 AM
Tiny
MICHAELPC
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  • 7 POSTS
I have the failed smog test results here and the only thing that didnt pass the second test was the EGR functional. It doesnt say fail, it just says N/A. Is that a costly fix?
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Tuesday, September 13th, 2011 AT 3:56 AM
Tiny
MICHAELPC
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The notes say: "failed test:emissions are too high, gross polluter, nox at both speeds. Whatever that means. Is there any way to tell what the problem could be?
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Tuesday, September 13th, 2011 AT 3:58 AM
Tiny
JACOBANDNICKOLAS
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NA means not aplicable. Perhaps that test isn't needed where you live.
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Tuesday, September 13th, 2011 AT 3:58 AM
Tiny
MICHAELPC
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So the comprehensive visual test passed, the functional check passed, but the emissions test says gross polluter and that I believe is why it failed the smog. Is repairing the vehicle to pass smog a pricey fix you think?
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Tuesday, September 13th, 2011 AT 4:02 AM
Tiny
JACOBANDNICKOLAS
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It really matters what it needs. I need to know what part has failed. Since you mentioned the gas cap, I am assuming you have en EVAP leak. That can be as simple as a rubber hose that is off or damaged, or require part replacement that can get costly. Were they anymore specific about the problem?
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Tuesday, September 13th, 2011 AT 4:06 AM
Tiny
MICHAELPC
  • MEMBER
  • 7 POSTS
No I dont see anything. Everything passed, but the measurement results are almost twice as high as the gross polluter limits. It really doesnt say jack unfortunetly and I dont know what to do. Im really broke and I need to get this fixed asap.
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Tuesday, September 13th, 2011 AT 4:14 AM
Tiny
JACOBANDNICKOLAS
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Can you contact the tech that checked it and ask for more specifics? I would be better able to help that way.
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Tuesday, September 13th, 2011 AT 4:16 AM
Tiny
MICHAELPC
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I can try to contact him tommorrow, the test was taken on 4/25/2011 so hopefully he'll remember and be able to tell me something. Thanks for help man and I'll get back to you when I find out more. Thanks again
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Tuesday, September 13th, 2011 AT 4:18 AM
Tiny
JACOBANDNICKOLAS
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I look for your email.
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Tuesday, September 13th, 2011 AT 4:20 AM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
Just to add this one here in california they test the gas cap off the car on a fuel cap tester machine on both thr obd1 and the obd2 cars. Also on the obd1 cars like yours that dont have on board diagnostics they do a nitrogen leak test by pinching off the canister line and pressure testing your evap system with a nitrogen cart. Sounds like you failed for two reasons bad gas cap not holding pressure and for too high of emissions gross polluter. Here in california if you get tagged as a gross polluter you have to go to whats called a referee station which is state run and operated.I would guess that very well could be the same in your state as well.I would ask the person that tested you.
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Tuesday, September 13th, 2011 AT 4:33 AM

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