A while back, my '88 Formula failed a smog test here in California, because it failed the EVAP test. The smog guy told me that 99% of the time it was just because the gas cap was bad. I ran out and bought a new gas cap but the evap test still failed. Can someone tell me what is being tested here? Is it just a test that the fuel system is closed? I have a smoke machine, where should I connect it. I have the factory manual but I can't find any mention of the evap system even there is clearly an evap canister. Any advice would be appreciated
The test detects vacuum leaks in the vapor recovery system. Yes the cap is the easiest fix, but the system has hard plastic lines and flexible rubber vacuum lines that often Crack and leak. I recommend getting a vacuum diagram for the evap system. You can then trace the system. Even a bad fuel pump sending unit "O ring" at the top of the fuel tank can leak and fail you.
The system is the fuel tank, the filler neck/cap, and the evap canister/purge valve. You can connect a smoke machine at either end - the filler or the purge valve. As Rick suggested, the leak could be at the tank in which case a smoke test may not show the leak, but it's certainly a good place to start. If you haven't, be sure all the rubber parts in the engine bay are in good shape. A leak at the valve is probably the most likely to happen and the easiest to find & fix.
87-88 Evap has a few things to look for leaks besides iffy cap... "Fiero type" Canister and purge valve is not included on the pressure test because the test should require the operator to pinch the vent line at the canister because the "dumb" canister never close the line to air.
Problems will happen when: The operator fails to seal that vent line. Old hard "rubber" hose makes this easy to happen or operator is using worn out pinch tool. Often all is possible. I remove the vent grill to give them easier access to the line because they won't and uses the tool at odd angles that fail to seal. Main Fuel tank is leaking air Vent line is leaking air. line is in two sections... main tank to aux tank, aux tank to canisters. Aux tank inside right rear "fender" is leaking air. Fill and vent tube set is leaking air. Fill ports have it's own vent.
Yes, Easy way is a smoke test on the fuel system. Only other way is pull parts out and look and that eats a lot of time/money.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
I had the same problem so i pulled the tank, wanted to anyway cause i bought a new sending unit from the fiero store , i replace every line looks like a new car , plus what i did is i pluged the vent line at the tank sending unit when i went to smog it and it passed lol, when i got home i upluged it . I live in trinity county/ shasta lake < were the carr fire was> you onle have to smog your car once in a life as long as you own it here, but LA county sucks for smog because i grew up ther until 2015 P.S if you need any evap parts i can get them , ther are about 5 fieros here at the local pick u pull
[This message has been edited by tazome (edited 01-19-2019).]
Thanks for all the great suggestions. I was just about to hook up my smoke machine when I noticed that almost every rubber hose in the engine compartment had totally disintegrated. I don't want to jump to conclusions, but I think this may be related to my problem. So I am now replacing every one of them. Luckily, it appears that the hard plastic lines are OK. The hoses that I am having the most trouble with are those near the cruise control actuator. That is because I do not have a diagram to show how they were routed before they turned to dust. Does such a diagram exist?
When I got my car smogged in San Jose, the guy had a separate gas cap tester that tested the cap off the car, that would tell you if it's the cap for sure, surprised he didn't have one.
When I got my car smogged in San Jose, the guy had a separate gas cap tester that tested the cap off the car, that would tell you if it's the cap for sure, surprised he didn't have one.
Yeah, I'm baffled about this too. Discrete gas cap testing is required unless you have an oddball car where no adapter exists (like an Alfa Romeo Milano). Pretty darned sure the Fiero is not such a car. I don't know why the tech suggested it could be the cap - his testing should have ruled that out. Although, maybe the cap testing only works one way - vacuum or pressure. I've never looked into it.
When I got my car smogged in San Jose, the guy had a separate gas cap tester that tested the cap off the car, that would tell you if it's the cap for sure, surprised he didn't have one.
Now that you mention it, I have seen the same thing. I wonder why it happened that way. The other possibility is that senility has kicked in and I am not remembering it right. The test was more than 9 months ago.
Just block Cruise Con vac line until you pass E-test. CC Vac lines are likely not only thing bad... can and valve under servo and servo itself are often leak problems.
I think you block a T port near CC "Brick" in 1 vac hard line to EVAP can valve.
[This message has been edited by theogre (edited 01-21-2019).]
My 87 failed evap last year because the fuel tank wouldn't hold pressure. The weld that held the evap line to the sending unit let loose. Bought a new sender, now I pass smog but my fuel gauge is horribly inaccurate lol.
I don't know why the tech suggested it could be the cap - his testing should have ruled that out. Although, maybe the cap testing only works one way - vacuum or pressure. I've never looked into it.
