Emission Difficulties - 78 GMC K-15 with Aux Tank

[akameriadoc]

Hi All,

I recently got a 1978 GMC K-15 Sierra Grande 5.7L from my parents.They owned it out in California and managed to get it pass emissions.

When I attempted the same out in Arizona it failed on the visual pass due to the vapor canister. Epoxy was used on one of the lines, due to a broken port. This apparently inst allowed in Arizona.

I managed to find another canister at a pick and pull.(5 port instead of 4 port)(probably bad). I still went ahead and got all the hoses connected and went and got it tested again. This time it passed the visual, but failed the actual test.

When it failed the second time on CO emissions at load. It registered a 3.72 out of a possible 3. Before it had been at a .11. It still passed on everything else


Could this be caused by any of the following:
1. Bad vapor canister
2. Hosing run incorrectly

Is there anything else that might have caused the change?

Also can anyone recommend a site or place to purchase a known good vapor canister. Cant seem to find one anywhere.

Any help would be greatly appreciated.

Other Notes:
1. New Engine
2. New Radiator
3. Carb was replaced with stock carb

[cjthompson]

Not sure if this is an approved method or not? I believe my main issue at the time was a defective converter though. I was always able to run it down the road in low gear for a few miles. I'd then pull in a parking lot about a mile away and bump the idle up to about 2000 rpms. It may knock your teeth out when you put it in gear, but I believe it was loading up when I sat in the parking lot. That's how I always got it to pass, may not work for you though...... I agree the problem needs to be fixed, but if you need tags, you need tags.

[akameriadoc]

Originally Posted by cjthompson

Not sure if this is an approved method or not? I believe my main issue at the time was a defective converter though. I was always able to run it down the road in low gear for a few miles. I'd then pull in a parking lot about a mile away and bump the idle up to about 2000 rpms. It may knock your teeth out when you put it in gear, but I believe it was loading up when I sat in the parking lot. That's how I always got it to pass, may not work for you though...... I agree the problem needs to be fixed, but if you need tags, you need tags.

Interesting fix.

Luckily I was able to get a 30 waiver and finally managed to get it fixed. The hoses were not run correctly from the canisters to the engine. Went from a 3.72 to 2.7. So happy it finally passed. Getting the tags later today.