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Thread: Evap pressure fail during emissions test

  1. #1
    LX User G. White's Avatar
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    Evap pressure fail during emissions test

    Passed the sniffer test with flying colors, however I failed the evap pressure test. Has anyone had any experience with this?

    The only components that were disturbed since the last emissions test was the fuel pump and sending unit. New Honda pump in original box (perhaps the last in existence) and a j/y sending unit from a low mile accord. Could it be a seal issue???

    Background info...had car parked out in the Arizona heat for the last 6 months. I would occasionally go out and start it. One of the things I would do beforehand is loosen the fuel cap and relieve the pressure from the tank (that swooshing sound) before getting in and cranking it over. The fuel tank has always held pressure just fine (during fill-ups and such).

    Recently, including today (emissions test day) that hasn't been the case...no swooshing...no pressure.

    I'm pretty sure they kinda disable the charcoal canister by clamping it off and performing the test. They clamped something off, I just couldn't see what from the penalty box they had me sitting in.

    The service manual mentions a 2 way valve as part of the evap system, and mentions how to test it with a vac gauge. Same with the canister...I'll test them if it comes to it.

    Just hoping that someone has some insight on this before I drop fuel tanks and get knee deep into this thing.

    Thanks everyone.



  2. #2

    Dr_Snooz's Avatar
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    Re: Evap pressure fail during emissions test

    Double check your work on the fuel pump and sending unit (through the hatches in the floor, not by dropping the tank). Most likely that seal has a problem. If that all checks out, I'd move on to checking the rubber hoses between the tank and the canister. I'd drop the tank as a very, very, very last resort (and only when the tank is nearly empty, of course). In AZ, there isn't much going to happen to that tank unless you've been rock crawling.

    FWIW, the way the shops check for leaks is to blow smoke into the system and see where it comes out. You could possibly pressurize it with a compressor and listen for the hissing if you felt like getting creative.
    Dr_Snooz

    "I like to take hammers, and just break stuff, just break stuff." - Beavis


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    LX User G. White's Avatar
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    Re: Evap pressure fail during emissions test

    Thanks Snooz!
    Yeah...I'm pretty sure both the sender o-ring and the fuel pump (lock ring seal?) were old. My car sat in a field baking to death in this heat all summer long. That pressure had to go somewhere.

    For what it's worth, the small section of lines I can see with the fuel tank installed look to be in good condition and aren't dry rotted.

    That brings me to my next question...has anyone found a suitable substitute for our evap canisters? They are somewhere between difficult and impossible to find. (There are a couple used ones, but who knows with used parts.) The 4th gen canisters look similar, but I'm just not sure. I'll do my due diligence and put a vacuum gauge on my canister as per the FSM and see if it's within spec. I'll report back with the results.

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    LX User G. White's Avatar
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    Re: Evap pressure fail during emissions test

    So I spent part of the morning making a DIY smoke machine to help me find my evap pressure leak. Once I had it all sealed properly, I hooked one end to my air compressor with around 5 psi and the other end I stuck down the filler neck. I packed it well with nitrile gloves and went into the trunk to pop off the cover plates for the sending unit and fuel pump.

    There was a strong fuel odor present until everything aired out a bit, but no evidence of fuel. Maybe the seals we were discussing?

    No smoke to be found anywhere except around where I had packed the gloves into the filler neck.

    The car was off (not running) and I had the bottom hose on the evap canister clamped off. Am I doing this right or am I missing something? When I was done troubleshooting for the afternoon, I stuck the smokey end of the hose up the tailpipe and once again packed around it with gloves. I found a couple of exhaust leaks (rusted holes) in the tailpipe forward of the muffler that produced smoke, so my machine isn't a total failure.

    I guess tomorrows job will be tracing the line that goes from the tank to the canister and looking at it up close, as well as ordering the fuel pump gasket and sender o-ring.

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    Dr_Snooz's Avatar
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    Re: Evap pressure fail during emissions test

    The fuel smell is indicative. I'm not sure what pressure the smog tech uses but it could be more than 5 psi.

    There's nothing special about the canister. It's just a plastic jar full of charcoal with some tubes on top. They all work the same way, so find something that fits and go with it. FWIW, if your car doesn't have a fresh gas smell when it sits around, the charcoal can is probably fine. You have a smell coming from the tank already so fix that first. Canisters don't fail often.
    Dr_Snooz

    "I like to take hammers, and just break stuff, just break stuff." - Beavis


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    LX User G. White's Avatar
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    Re: Evap pressure fail during emissions test

    Snooz, you're right...That's exactly what the evap pressure test is geared towards- gas fumes so I will let my nose be my guide.

    In hindsight, I think I was wasting my time with the smoke machine because they are mostly used to find the large leaks and not the very small ones.

    I'm going to drop the tank and replace the rubber hoses with ethanol friendly stuff. My car sat with a 1/4 tank of year old fuel in the heat and I would bet dollars to donuts that the ethanol took its toll on things.

    I'll have better access to the fuel pump and sending unit and can ensure I get a good seal when replacing those gaskets. There are few components, the two-way valve (which opens and allows fumes to go to the canister) and the fuel cut-off valve and liquid vapor separator (that keep liquid fuel from entering the two-way valve) that I need to troubleshoot and inspect.

    Now to drain that 7 gallons of fuel that I put in the car for the emissions test........

  7. #7
    LX User G. White's Avatar
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    Re: Evap pressure fail during emissions test

    Today the tank got dropped like it's hot. I didn't find anything destroyed, but did find a couple things. First off, the o-ring for the sending unit looked like it didn't seat properly and got a little smashed on one side when I installed it last. Secondly, the section of black fuel line going to the fuel pump was breaking down. There are only two locations that use that type of hose (the other being a small section of the return line next to the high pressure line that enters the car) and that hose was beginning to break down.

    I think my vacuum gauge is junk because it doesn't hold pressure no matter what I do to it. I didn't have the chance to check the two-way valve...that will be tomorrows chore when I replace the fuel lines.

    -img_0953-png -img_0954-png -img_0957-png
    Last edited by G. White; 09-22-2019 at 06:40 PM.

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    LX User G. White's Avatar
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    Re: Evap pressure fail during emissions test

    Today, I passed the evap pressure test...here's what I learned along the way. The hoses and fuel sending unit gasket may have contributed to my previous failure, but I think the real problem was the two-way valve that rests on a bracket next to the fuel pump...That's where the fuel smell was coming from when I removed the left access cover.

    I had to find a pressure gauge that not only created vacuum, but was also able to produce pressure. Like I stated before, my cheap gauge was absolute garbage and this gave me an excuse to buy a much better one. As per the FSM, I needed vacuum and pressure to properly test the two-way valve. My valve held vacuum but steadily leaked down when pressure was applied. I submerged my valve in the bathroom sink and found out that the seal on the housing was shot. Of course they don't make them anymore, so I ended up sealing the perimeter with black sealant. Once that dried, I checked it again and discovered the tiny vent on the valve leaked pressure. I'm not sure if that is the way that it is supposed to function, but I wasn't taking any chances and I sealed that too.

    Everything got put back together with new hoses and clamps and the car fired right up. Most importantly, when I removed the gas cap, the tank had pressure again. As a bonus, my idle was much smoother.

    So, in conclusion I may have turned my two-way valve into a one way and might have to keep an eye out for vapor lock...but the forty miles that I drove today was thankfully uneventful. I can celebrate because I passed emissions and can enjoy this car for another two years.

    I know this was a long-winded, uninteresting thread that will probably get buried in the archives. If it can help just one person in the future and keep another of these wonderful cars from being squeezed in the crusher then my time was not wasted.

    Now on to other things like the play in my steering and brakes that don't make me feel all that confident when applied..........
    Last edited by G. White; 09-30-2019 at 11:29 AM.

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    Re: Evap pressure fail during emissions test

    Quote Originally Posted by G. White View Post
    Now on to other things like the play in my steering and brakes that don't make me feel all that confident when applied..........
    OMG. It's like I wrote this myself!

    Glad you got it all working again.
    Dr_Snooz

    "I like to take hammers, and just break stuff, just break stuff." - Beavis


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    LX User G. White's Avatar
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    Re: Evap pressure fail during emissions test

    Quote Originally Posted by Dr_Snooz View Post
    OMG. It's like I wrote this myself!

    Glad you got it all working again.
    Thanks Snooz....we practically have the same car...probably same problems too!

    -img_0863-jpg

  11. #11

    Dr_Snooz's Avatar
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    Re: Evap pressure fail during emissions test

    LOL. Seems so. You need to give me your drop, or I need to give you my rims. You can keep your problems though.
    Dr_Snooz

    "I like to take hammers, and just break stuff, just break stuff." - Beavis


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