Emission Difficulties - 78 GMC K-15 with Aux Tank

Akameriadoc · January 5, 2016

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 a visual pass on 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 vapor 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.

This time it failed on CO emissions at load. 3.72 out of a possible 3. Before it had been at a .11. It still managed to pass 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

THORX4 · January 21, 2016

3.72 and you need a 3 try some "guaranteed to pass" http://www.oreillyauto.com/site/c/detail/CRC6/05063.oap works everytime. As for canisters do a search on used auto parts or use this link. Any place that has them will be listed. Alsio check ebay.http://www.car-part.com