the fuel pump activates, there is spark at a plug I tested, there is positive voltage at the injector I tested. But there is NO ground path to the injector. Therefor of course they don’t activate and the car wont start. I checked out a shop manual from the public library and my understanding is that the crank and camshaft position sensors when working send through the ASD relay the positive voltages to these actuators, so I am thinking the crank and can position sensors are not at fualt. This leads me to think the PCM is at fault or the harness to the injectors. Can you help me with the ground path to the injectors. Or how do I determine what is not happening to EXCLUDE a ground path to the injectors. I used both a digital voltmeter and a noid light to determine that there is no ground path while cranking the engine. 1999 300 m
On your 1999 Chrysler 300m, when the ignition switch is ON, there is always voltage at the fuel injectors — that’s the positive path. The ground path goes to the engine computer (PCM). The PCM makes the ON connection, to the chassis ground, to energize the fuel injector for each spray. The PCM opens the ground path to stop the spray. When the engine is running, this on and off happens many time each second.
The PCM controls the fuel injectors. The camshaft position sensor, and crankshaft position sensor, send their signals to the PCM. Without a signal from one (maybe, both) sensors, the fuel injectors won’t be energized by the PCM.
The ASD Relay controls power (12 volts) to the PCM. Without power, the PCM wouldn’t produce spark, either.
As hellokit sez, it could still be the crank/cam sensors. They need to be tested.
appreciate your fast reply greatly ! I am still perplexed a bit as my shop manual says verbatim the folowing :
IF THE PCM RECEIVES THE CAMSHAFT POSITION SENSOR AND CRANKSHAFT POSITION SENSOR SIGNALS, IT ENERGIZES THE ASD RELAY AND FUEL PUMP RELAY. IF THE PCM DOES NOT RECEIVE BOTH SIGNALS WITHIN APPROXIMINATELY ONE SECOND, IT WILL NOT ENERGIZE THE ASD RELAY AND THE FUEL PUMP RELAY. THE ASD RELAY AND FUEL PUMP RELAY SUPPLY BATTERY VOLTAGE TO THE FUEL PUMP,IGNITION COIL AND HEATED OXYGEN SENSORS. (does battery votage mean positive voltage … I do have that ) it appears that if the asd relay works that the crank and cam position sensors must be also … what am I missing.
I am really appreciative that I am talking to someone. I can take the crankshaft sensor out easily or at least check the voltages at the harness connection. The cam sensor involves removing the intake plenum which I’d like to avoid. I think I should be ablle to stick some paper clips in the back of the connectors to check reference volts etc. What say you