For 12 years I’ve owned this ‘76 12C but the car is rarely driven. I’ve been giving it some attention the last few weeks and it occurs to me it has slowly (over years) become more difficult to get running when cold. The engine cranks fine, fires a little and then quits. Next turn of the key fires a few more times than before, but won’t stay running. About the 4 or 5th try, the engine keeps running, but it is best described as, “slowly comes alive to a 700-800 rpm.’ The idle isn’t too rough, but not smooth either. The car starts quicker when fully warmed up.
The first items investigated on the list include the components which add enrichment and air needed when cold (cold, in Dallas, the air temperature in April/May is anywhere from 50F - 80F.)
AAV - I pulled the AAV thinking it was stuck closed. Nope, fully open. Tested while in hand in water and it fully closed rather easily.
Water Temperature Sensor - I removed the ECU connection clip in the trunk to test the harness wiring and the temperature sensor. At 68F, the ohms reported was 2.8K, fairly close to expected per chart. Certainly a close enough signal for the ECU to add fuel.
Fuel Pressure - I have a permanently mounted fuel pressure gauge which tees off one of the cold start injectors. Turning on the ignition, the pump runs for a few seconds, turns off waiting for cranking. The gauge reads 29-30 psi which is correct.
So what’s next? While the ECU connector is acceptable, I ran down the list of devices and various pins to check for correct signals. Everything reported properly.
I did vacuum simple test also the MAP Sensor to ensure it holds a vacuum and it does.
So now it is time to turn to ignition.
I pulled the 12 spark plugs and they all looked very similar - tarnish to dark brown. All gaps still at .035”. Not many miles on the plugs and the plug leads (wires). I cleaned up the plugs, chased the threads, a little anti seize, and put the plugs back in.
As I stood with a beer and gazed at the engine deep in thought. It occurs to me that this engine doesn’t “jump” to life like other engines. Makes me think I’ve had some kind of ignition retardation creep over the years. (As if the distributor isn’t tight to the engine)
Even when it started better a few years ago, it didn’t run at 1,100 rpm while the AAV was open and then calm down to 750 as it warmed up. Makes me think I have retarded timing.
So I pulled off the distributor cap to check the rotor and cap. A little corrosion but I sure have seen a lot worse. (Years ago I converted to the Lumenition system)
I tested the vacuum advance, and it wasn’t responding. No vacuum pull at all. So I’ll order a new one.
I’m thinking I have to pull the distributor to replace the vacuum advance, but stopped for a break. I removed the trigger board. It looks rather corroded or something on the downward facing side. See photo - anyone seen this before? Is it a problem?
Any chance of replacing the vacuum advance without pulling the distributor? I see about 1/8” of a split pin sticking up - holding it in place?