Went through emissions today with my 83' GS 12A, with the carb leaned out and a new catalytic converter, properly working air pump system. the carb is relatively new and in proper working order. All of the rats nest is fully in tact with no holes or dry rotting. The car failed emissions on hydrocarbons and no's. The car passed flawlessly
the previous year. I basically need to find out if replacing the fuel pump with a direct O.E.M pump would cause the car to fail on hydrocarbons due to the correct fuel delivery. If anyone has experienced this before A helpfull tip would be greatly appreciated. Oh, the car has 172k on the original block.

Thanks

 

Can you post all of the emissions numbers, including CO, CO2, HC, and NO?

This will help in diagnosing the problem.

RXDad

 

That and elaborate on what you meant by "leaned out carb". If you lean it out too much you'll fail HC easy due to misfires at idle dumping fuel into the exhaust unburned.

Using a replacment pump wouldn't cause the problem.

Vernon