Crankshaft position sensor

Tiny
ARTIST723
  • MEMBER
  • 1990 DODGE RAMCHARGER
  • 5.2L
  • V8
  • 4WD
  • AUTOMATIC
  • 126,000 MILES
My truck with 318/ 5.2 would stall out at times and within a few seconds I could restart it. Then it started to cough a little on my way home from work, and finally just shut off all together. So I found out it was not getting spark. So I replaced the distributor, coil, shut off sensors spark plugs wires cap and rotor. Now the only thing I can think of is the crankshaft position sensor, but I cannot locate it. Everywhere I search this information says it should be on the passenger side top at the bell housing, but it is not there. I called the dealership and they ran the VIN number, and said it should be part of the distributor, but all the parts stores say that it is separate. Where to look next?
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Monday, September 26th, 2016 AT 3:17 PM

3 Replies

Tiny
CARADIODOC
  • EXPERT
It is indeed in the top of the bell housing right behind the right cylinder head. It has three wires. It has a very critical air gap that is set by a thick paper spacer glued to the end, or a thin plastic rib molded on the end. With either of those, be sure to push the sensor in as far as it will go, then tighten the bolt.
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Monday, September 26th, 2016 AT 3:39 PM
Tiny
WRENCHTECH
  • EXPERT
Hi Doc, Alldata says it is in fact in the distributor. It uses a hall effect sensor to do the job of the Crank sensor.
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Monday, September 26th, 2016 AT 4:28 PM
Tiny
CARADIODOC
  • EXPERT
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.
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Monday, September 26th, 2016 AT 6:27 PM

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