You gotta have 12 volts too to the injector. I'm not familiar with your specific engine, but I can share how 99 percent of these systems work.
12 volts to run the injectors, ignition coil(s), and fuel pump or pump relay comes from a main relay. Chrysler calls that the automatic shutdown (ASD) relay. It can also be called the fuel injection relay, ignition relay, or something like that. The Engine Computer turns that relay on when it sees engine rotation, (cranking or running), and it knows that by the pulses it gets from the crankshaft position sensor and the camshaft position sensor, (which could be inside the distributor.
This is done for safety reasons. If a fuel line gets ruptured in a crash, the fuel pump would dump raw fuel onto the ground creating a serious fire hazard. With a leaking fuel line there can't be any fuel pressure. With no pressure, the engine can't run. With a stalled engine, there's no pulses from those two sensors, so the computer turns the relay off which turns off the fuel pump, along with other circuits.
That means you have to check for the 12 volts feeding an injector while cranking the engine. Chrysler also turns the ASD relay on for one second after turning on the ignition switch, and before you crank the engine, to insure fuel pressure is up for starting. A lot of GM models turned the pump on with a tap on the oil pressure sending unit. It was the same principle. If the engine stalled, there would be no oil pressure so the fuel pump would turn off.
Getting that 12 volts to the injector is the first half of the story. Next, the computer turns the ground wire on and off to pulse the injector. The amount of time of each pulse is very precisely controlled and adjusted. I've never actually examined the "duty cycle", but as a guess, I'd suggest 30 percent is normal. That means the injector is pulsed on for 30 percent of the time, and off for 70 percent. Your ground wire is holding it on for 100 percent of the time.
If you have spark, the cam and crank sensors should be working, but this is where there can be major differences in how the systems work. Most engines will have no spark or injector pulses if the signal is missing from either sensor. Some engines will continue to run on one sensor when the other one fails, but it won't or may not restart after the engine is stopped. Some engines will run with one failed sensor but at reduced power.
Friday, September 26th, 2014 AT 4:57 PM