At the suggestion of someone on the Chevy forums, I replaced the K2500’s coolant temperature sensor. There are actually two: one in the intake manifold (the one I replaced) which feeds data to the computer, and one in the driver’s side head (which does nothing more than run the temperature gauge on the dashboard).
It made no difference, unfortunately. The engine runs the same and the SES light is still on.
While I was working on that, I took the air filter housing off and looked at the injectors’ spray patterns with a bright light and while the engine was running. Instead of a fine mist, the injectors are dribbling fuel down the bores. I could actually see individual drops of gas running down the throttle body walls. So no wonder why the engine’s running so rich. It’s time to replace the injectors.
I charged the air conditioner, too. Unfortunately, that made no difference; the compressor clutch seems to be disconnected, and I can’t find where the connector is. Without it, the AC’s not going to do anything. And to top it off, once I shut down the engine I could hear the refrigerant leaking back out of the system somewhere near the consensor. So I’ll need to fix that before I try to recharge it again.
Also, I suppose I should pull a vacuum before I try to charge it again. Who knows what moisture there is in there.
I successfully added refrigerant to the Ram, too. Formerly the compressor was cycling on and off and it wasn’t blowing as cool as I wanted. Now it’s staying on constantly and the low side pressure was staying at about 40 PSI. High side was approaching 350 PSI, but it was also a hundred degrees outside when I was working on it.
I ordered two fuel injectors from Rock Auto, which include hardware (presumably, O-rings and gaskets).