The crankshaft position sensor behind the right cylinder head was used along with the camshaft position sensor in the distributor on 1992 models, but both sensors are listed for 1990 and 1991 models too. Go figure.
There were actually two different designs, but those were for 1989 models. Both were in the distributor. One used just two wires. That was a magnetic coil similar to what was used way back to 1972 on Dodges. The other was a three-wire. That was the Hall Effect switch. It needs a ground and a power wire for the internal circuitry, and the third wire for the signal pulses.
In 1992 they went to the sensor behind the right cylinder head. All of those were three-wire Hall Effect sensors. If there is not one on your engine, that would agree with Wrenchtech and Mitchell-On-Demand, but not my source for looking up parts. My comment about needing the spacer was wrong too. That only applied to the front-wheel-drive cars and minivans with the 3.3L engine. This one for the 318 is just bolted in with two bolts. No adjustment is needed.
There were different versions of this system too. With most of these crank sensors there was still another three-wire Hall Effect sensor in the distributor, but they called that the camshaft position sensor. The flywheels had groups of four notches, or cutouts that were detected by the crank sensor. There were three of those groups for the V-6 3.9L and four groups for the V-8 engines. The camshaft sensor told the Engine Computer when a piston was coming up on top dead center, but the crank sensor's information was much more precise. The distributor was needed to send the spark to the right cylinder.
In later years they used a different number of notches in one of the groups on the flywheel, and the computer used that to identify which pistons were coming to top dead center, so no distributor was needed. Those engines used an ignition coil pack instead of a single coil.
The Hall Effect switch design in the distributor shown for 1990 models is similar to what was used in the distributors of the 2.2L and 2.5L front-wheel-drive engines, and those had a very high failure rate. If you installed a used distributor, it wouldn't surprise me if it has an intermittent or dead sensor.
It seems it was necessary to add even more confusion to the story when it comes to troubleshooting this system. You need to start by checking if the automatic shutdown relay is turning on. That is easiest to do by measuring the voltage at either injector, either smaller wire on the back of the alternator, or the twelve volt feed wire for the ignition coil. Those are the dark green / black wires anywhere under the hood, except for the ignition coil. There it is the gray wire. Use a test light since most digital voltmeters do not respond fast enough. You should see twelve volts there for one second after turning on the ignition switch, then it will go back to zero volts. You might hear the fuel pump run for that one second too.
What is important is that twelve volts must come back during engine cranking. If you never see twelve volts at the coil, we have to look at the twelve volt supply and the relay circuits. If you do have twelve volts for one second, that proves the circuitry is okay and the computer has control of the relay. If the voltage does not come back during cranking, that is when the distributor pickup assembly is in question. Let me know what you find.
Monday, September 26th, 2016 AT 6:27 PM