Hi guys,
I picked up a copy of your newsletter at the French-Italian car show last week, and have also browsed your very informative web site. I have a 1978 124 spyder that has trouble passing the California smog test due to high CO levels (twice the limit at both 15 and 25mph). The HC and NOX levels are fine. I just rebuilt the carb, and it appears to be in good shape. I noticed in your November 2000 tech tip that some carbs may have had the jets changed, so I looked at mine. The primary has a 125 gas jet and a 170 air jet, and the secondary side has a 140 gas jet and a 170 air jet. Does that sound right? The car supposedly has only 70,000 miles on it, so I don't think the catalytic converter is bad, but the air pump system might be. Can you tell me how I can check it out? Any ideas would be appreciated. Thanks, Kevin

First off, unfortunately I have no experience with the rolling dyno test you obviously are referring to. We still have the idle/2,500 RPM test here in Santa Cruz. I also only have personal experience troubleshooting for this kind of test, and it has been easily five years since I did that!

Always the first things to check are what any good smog technician will obviously check first... The car is in the correct state of tune, valves properly adjusted, no vacuum leaks, and all the installed smog equipment in excellent operational condition. Your feeling that the catalytic converter is not bad I feel might be incorrect. With your mileage, assuming it is the original cat, it is probably bad. Often to get late 70's car to pass today's requirements requires a new cat every few tests!

According to Fiat, your primary main should be 1.25, the idle .5, the e-tube F73, and the air corrector for a CA version of 1.75. If your car is 49-state, make that 1.85. During the test, the secondaries do not come into play, at least here.

The only way I know to test the air injection system is to remove the manifold from the head and using shop compressed air, see if all the passages are clear. The air pump should be pumping air thru it during all times except decelleration. Low flow at low RPM could be causing your cat not to light off at low speeds, especially if it has as many miles on it as you say.

Remember that honest technicians take pride in getting older cars to pass state requirements. All you've got to do is find one of them! Doing smog test preparations on a failed car at home is basically impossible unless you can afford to purchase all the state required equipment for your local test.