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Spent a fair amount of time with a multi-meter today attempting to diagnose the health of the D-Jet on my '72 142.
The symptoms: Very difficult cold starting, car eventually smooths out when you give it enough gas, and will idle smoothly once warm.
The preliminaries: Plugs, points, spark plug wires all changed for new, new cap, rotor and condenser. All vacuum and fuel injection hoses changed for new. Fuel pressure checked and is spot on. Engine timing, dwell and idle all set within recommended ranges.
Cold start injector: Pulled it and it is not leaking and operates properly when starter is cranked. Curiously, cold start injector also worked on cold engine when temperature sensor by thermostat was disconnected (does this signify a bad temperature sensor?)
Throttle switch: Listened for clicks when manually operating the throttle. Never got a full 20 clicks. Typically got 18 clicks (although would get 19 clicks one out of every 10 tries). Any thoughts on how to adjust the switch to generate the full 20 clicks?
ECU: Pulled the plug and went through the dianostic using the excellent Phil Singher guide at V Classics. Everything was within normal spec (trigger points, pressure sensor, temperature sensor 2, temperature sensor 1) EXCEPT pin 5, where multi-meter showed a completely open circuit. Per the wiring diagram in my Haynes manual, pin 5 operates the injector on cylinder no. 4. A completely open circuit would mean that injector no. 4 would be squirting fuel constantly, wouldn't it? (the car certainly doesn't sound as if it's running on three cylinders). Wiring to injectors on cylinders 1 and 2 was degraded and I repaired it, but I couldn't see any evidence of frayed or broken wiring on the injector for cylinder 4).
Any way to check the operation of the injectors other than pulling the entire fuel rail?
Any thoughts on what this all means? Anything else I should be checking?
Thanks for the help!
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