Fuel Evap Test FAILED

[jadppe]

I just got back from Smog shop (California) and passed everything but Fuel Evap Test. I got a 78 FI. And the way I understand it is they pressurize the fuel system and look for leaks. He says there is a big one but has no idea where. I have noticed when I fill up with gas that I smell it in the cabin if I fill it all the way.

So would I be correct in thinking it has to do with filler neck? I don't smell gas in the engine compartment usually so I'm doubting it's a leak in the evap system.

Also I see in some diagrams that there is a tee off (more like V) to a smaller tube off the filler neck that I believe must be part of evap system. Do I have one of those in my 78?

Thanx in advance

Joshua
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Currently trying to fix up a 78 sunroof bus. 3rd bus in my life...2 late bay westies previously.

[soniq]

look in the engine compartment and over to the left under the spare tire wheel well. hiding up behind that is a little connection where the fuel hose will usually be cracked/leaking, and often gets missed when replacing the rest of the fuel lines.

when I had gas smells at every fill up, this was the source.

[SGKent]

if you have not been through the evap system you will have to. The bus system will never pressurize because the side that feeds it air is always open. However if you have a big leak it could be the cap, the neck, the hose from the filler to the tank, the o-ring around the fuel sender, any of the hoses connecting evap lines to the tank, the hose under the spare tire or the hoses in the back of the bus where it connects to the canister. It can also be a evap bulb or line in the vents rotted out. Your mission if you accept it is to find where. When they test my 1977 they only test the cap. And the Blau caps leak even when new so they usually work around that one as it is also a problem with the design of the test gear for that year car. I think the blue or yellow adapter is too small or something like that when they test the cap and my understanding is it has been reported to CARB for VW's and Mercedes which use the same colored adapter.

[jadppe]

Thanks gentlemen. So when they do the test, they leave the cap on? I do have the German locking gas cap from bus depot. Hard to tell if it seals. I'd be psyched if it was just that but a little pissed cuz I just took out the filler neck through the pie plate hole because I was sure it was the filler neck but when I tested it I couldn't blow air thru it with my hand on the other end. No leaks there or at the other rubber tube that joins the hard pipe to the tank.

I passed smog 2 years ago except he said my gas cap wasn't sealing and he sold me a cap that made it work. Could it be he saw the newer cap and didn't question the seal or is there a separate test for the cap vs the evap system? I think atwell had a video on how they do the test. I'll check that out.

I did feel the short tube under the spare tire well and it seems intact and doesn't smell of gass but hard to tell without removing it. Charcoal canister is all hooked up and tubes seem fine. I'll check again.

Also. Is there a way to check the pressure yourself? Or just gotta check every hose?
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Currently trying to fix up a 78 sunroof bus. 3rd bus in my life...2 late bay westies previously.

[SGKent]

There should be two metal lines just forward of the rear license plate light hanging down. You can join them together with a tee and put a little vacuum on them with a hand vacuum pump. It takes about 10 minutes of pumping and the tank will creak as you remove air and it starts to collapse. Only pull a tiny amount of vacuum until you see the needle move then wait a few minutes and see if it holds. I would NOT use compressed air cause you might blow a hose off or pop a fuel line and spray fuel. It will take less pumps on the vacuum pump if the tank is near full. If that holds a vacuum then the system is sealed. The canister has 3 connections. One is to the air box, one is to the two metal lines and a tee and the other on a 1978 goes to the 1-2 cylinder tin. The cylinder tin blows air through the canister to purge it when the air box is drawing air. That hose to the tin is ALWAYS open. This means that if someone tried to test for a vacuum leak by sucking on the tank filler, air would travel up through the tin, into that hose, into the canister, into the vapor lines and out the filler neck, looking like a vacuum leak. One the other hand they do expect the gas cap to seal so use the one the guy gave you when you go into test.

[larrydeville]

The smog teck will pinch off the small line that goes from the cannister to the tee connecting the small metal vapor lines close to the engine rear door. The cannister and hoses to the air box are not part of the test. A adaptor fitting is installed replacing the gas cap so the evap testor can gently pressurize the tank with nitrogen and teast for leak. The cap is tested by itself. My non locking cap will fit on one of the adaptors on the cap testor. My 77 camper needed the filler neck rubber section replaced and the tee going to the cannister....now all ok....The smoke machine is great for finding the leaks...Visual...flashlight and look for gas stains.....Thx...Larry

[Desertbusman]

Stick the hose from the outlet of you shop vac on to the filler opening. Use a spray bottle with soapy sudsy water. Check everywhere looking for bubbles.

That might be a quick and easy way to find the leak causing it to not pass. But you really need to lower your engine a bit, pull the firewall and start replacing all the hoses on the fill neck and all the vapor recovery vent lines and connectors. I helped a friend a bit doing his and it's a bitch.
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71 Superbug
71 Westy

[GeorgeO.]

I had to reseal my gas tank which required me to take apart the fill neck hose. Well the straps that held it in place were loose. Good thing that rust came out of fuel filter or else I never would of found it. So check your hose and good luck.

[Millennium Falcon]

[skills@eurocarsplus]

[Desertbusman]

Chicken No need for inert gas. I doubt you, your engine, or your tank normally breathe it. Now my vac hose is about 20 feet long so the vac isn't anywhere near the tank. Should I fill my bus with inert gas next time I vac it?
Naturally you would want the vac blowing before you stick the hose in the filler.

Use compressed air if you want to have an experience. I doubt any of us have a regulator or gauge to keep it or 2 psi. I gave a couple shots only with my air nozzle and the flat bug tank went round.
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71 Superbug
71 Westy

[SGKent]

I had this vacuum once hooked up to something similar but smaller and some fumes from a carb cleaner got sucked in. The sparks from the brushes............... well at any rate I don't own the vacuum anymore. In fact I should have known better cause I cleaned skill saw bearings once with a cleaner like WD-40, fired it up 5 minutes later and the skill saw fan inside the motor and the brushes made it into a flame thrower - about 3' followed by a poof as I let the trigger go. It still works. Don't think I would try a vacuum on a fuel tank.

BTW - all these folks running around with smoke testers. I guess the recession is over. Most are $750 to $1500.

[skills@eurocarsplus]

well do as you wish. i know you love manuals, so read this

http://www2.otctools.com/otctools.com/newcatalog/products/107360_E.pdf


the inert (nitrogen) gas is to keep everyone safe as possible. but whatever. if you want to have a shop vac hooked to any part of the fuel system, i applaud you for being the next Darwin Award winner.

yea, it's a 1,500 tool. but it is what it is in my line of work. also works killer for checking for oil leaks before you start an engine.
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[SGKent]

[skills@eurocarsplus]

SG, if you had a bunch of friends you could charge a small fee to help offset the cost i would totally reccomend one. it's uses are endless.

i agree most can't justify the expense. i have some pretty expensive tools that only get used on rare occasions. i look at it this way, it's not about need, it's about have

FWIW, my lift...delivered was about 100.00 less than the smoke machine
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[jadppe]

OK, putting that filler neck back on was no picnic but the things I checked were:

#1, 7 and 6 and all were fine. The fuel sender cap felt solid. BTW, I do have the hole cut out above fuel sender.

Now because of the hole in metal above the tank and the smell of gas INSIDE the cabin (not in engine compartment), I would guess it would have to be either the tank itself or the #12 above and the #24's around it. Then all the other things in that area that I checked yesterday.

Does that sound right for gas smell inside the bus? There's no way for fumes from the engine compartment to get into the cabin, right?

I am going to replace all the rubber hose pieces in the system (except for the filler neck stuff). Can I get that stuff at a FLAPS? I don't quite understand the sizing on Atwell's site 7X2.5mm? Is that 2.5mm hole diameter and 7mm outside diameter?
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Currently trying to fix up a 78 sunroof bus. 3rd bus in my life...2 late bay westies previously.

[Air_Cooled_Nut]

Using a vacuum, be it shop vac or house-hold unit, isn't a good idea because of the plastic hose. Air rushing over the plastic can cause a charge to build up -- remember the trick of rubbing a balloon on a shirt then holding the balloon over someone's head with long hair? With gasoline vapor it just takes a spark...
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Toby http://www.aircoolednut.com/
Did I mention that I'm an original Darksider?
'72 VW Squareback, 2007cc, GB 5-speed, rag top; '76 VW Riviera Penthouse Sundowner 2.0L; 2015 Audi S5 Cabby w/Stage II APR; '06 Ducati Sport Classic 1000; '14 Ducati Diavel Strada
The First Invasion

[tootype2crazy]

I had a strong gas smell and it turned out my sender wasn't seated correctly. Since you have the hole, check that.
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air-cooled or nothing for me
1978 Sunroof Deluxe Bus (daily driver)
1978 Transporter (mom's, making into a camper)
1970 Single Cab 2.1 turbo/EFI 6 Rib, 78 front beam, vanagon backing plates on rear (project)
2001 GTI VR6 (wife's)

[SGKent]

there is an o-ring around the sender on late bays and as I recall a gasket on early bays. The 0-rings crack and leak with age.

[williamM]