Evap test fail

[redrider90]

So recently my check engine light on my 2002 civic came on. It coded as a high fuel tank pressure sensor high. After a careful evaluation I replaced it with an OEM unit.  CEL immediately went off and I cleared the code and took it for a long ride. After returning I put the OBDII unit on it and ran it through diagnostics. It showed no codes but when I had it test the evap it said said the test failed for a leak. Yet it doesn't throw a code nor does the CEL on the dash light up. I looked on you tube but virtually all videos were about EVAP leaks showing either a P1456 or P1457 code. I do not have a code.
If it had an EVAP leak I would expect CEL to light up and have a code. I do not have a smoke machine. I have thought about using my universal gas sensor to try to find a leak. It is very sensitive to all fumes. But anybody have any ideas out here about what I am facing. This is an older car in great shape but its computer system does not have as many diagnostic functions as say my 2011 Hyundai which will identify all the sensors on the EVAP system.

[guzzisteve]

If you changed all hoses it shouldn't have a leak. Unless too clean means you have a leak.
My 00 Cherokee was throwing evap codes on dash for years, thought it may be the gas cap. couple years ago I had an injector stick open. Fuel rail was total goo. New injectors & fuel additive had me an error twice about too much catalyst. Additive was doing it's job, fuel rail clean AND no more evap errors since.

[redrider90]

Thanks for the reply. BTW it has been sitting there for a couple of days and I opening the gas cap and it made a whopping sound. Seems like it was holding vacuum. I don't get that part.

[guzzisteve]

I think the fuel vapors cool at night, getting smaller it creates a vacuum. Doesn't sound like a leak does it. My cat was stolen in IL, so I haven't one of those, but still an O2 and it works. The fuel additive I use is DurAlt. I cleaned up my other 4.0 motors with it. Where all the plugs were not same color before and after a pint or so they were identical. Only stuff I've found that does what it says. Harley shops sell it as their fuel conditioner.

[redrider90]

What's worse is it just now threw the original code at me for a high fuel tank pressure sensor at me. WTF
I put the new one on and the CEL went away before I even cleared the code. I drove it 50 miles and put gas in it and shut it on an off a dozen times and let it sit 2 days and it throws the code. I checked the connections before I even bought an OEM unit.

[Stretch]

Those EVAP codes can be awful

I had one on my '04 Honda Element.
I could smell gas after a fillup - but no
one could find the leak. So, I rode it around like that for
most of a year. Then one day I was filling it up, and as it was
getting full, gas started pouring out underneath the car!

AHA - A CLUE!!!   

Turns out the filler pipe from the cap to the tank had developed
a pinhole from rust. It wasn't obvious until it became a BIG hole.
Enough to throw a code at first, but not enough to be obvious.

Check yours and see how manky it is.

                                    -Stretch

[RinkRat II]

      Gas Cap??  Some O'reillys and Auto Zone will test for free.

      Paul B

[nc43bsa]

Some of the OBD-II codes have to be detected several key-on/key-off cycles before it will set and turn on the CEL.  That's why you can drive away from the gas station with the fuel cap hanging from the tether and the light won't come on, but if you keep starting/stopping the engine all day with the cap loose, it will.

My 1999 Buick has shown a P0442 code (small EVAP leak) for a few years now.  I replaced the cap, since I think it was the original one, but the code came back.  Since the car is now over 20 years old, and no longer subject to the state emission test, I'm ignoring the CEL.  I don't have a smoke machine, and the going rate for a CEL diag is $100.

[s1120]

Some of the OBD-II codes have to be detected several key-on/key-off cycles before it will set and turn on the CEL.  That's why you can drive away from the gas station with the fuel cap hanging from the tether and the light won't come on, but if you keep starting/stopping the engine all day with the cap loose, it will.

My 1999 Buick has shown a P0442 code (small EVAP leak) for a few years now.  I replaced the cap, since I think it was the original one, but the code came back.  Since the car is now over 20 years old, and no longer subject to the state emission test, I'm ignoring the CEL.  I don't have a smoke machine, and the going rate for a CEL diag is $100.

This..  It might not have set the code yet. Most systems run the test during set conditions, and it will have to fail a set number of times. I would just run it and see what happens.