My '76 XJ12C is having cold start difficulty. I first thought it might be related to the AAV, but when removed I discovered it was open as it was cold, and of course because it was in my hand, I heated up the bulb to see if it would move. I used a heat gun for the inaccurate quick check and indeed the valve closed quickly/easily.
My next thought is the water temperature sensor for the ECU. I can’t find my books because I moved and have many boxes of books unopened, but I know there is a chart with a range of resistance as temperature changes. So I thought, probably easier to just purchase a new one. I believe the part number is C42166, but I can’t find them. Is there a substitute Bosch part number or Jag part number?
I found on the jetronic.org website that the Bosch part number for the ECU water temperature sensor for D Jetronic is 0 280 130 014 or Lucas 0 280 130 025.
This evening, I took my ohm meter and the two pins measured 2.8k ohm across. That is in range for the 68F of the engine/garage.
I’m questioning why my engine is suffering from hard starting. I have 30 psi fuel pressure and my AAV is open, so I thought maybe the water temperature sensor was failing, but it looks correct for current cold engine. Next, I measured the ohms on the 23rd pin at the ECU which corresponds with the water sensor and it was 2.8k ohms so the harness isn’t the trouble.
Maybe I should have started a thread topic on V12 hard starting.