91 5.2 will not start

[gnemac]

91 5.2 dakota died on way home from work. Has not started since. Have replaced coil, distributor cap, rotor, pickup assembly in distributor. Checked wiring harness for bad splices they are all ok. This particular truck does not have a crank sensor on it. I have power going to coil but nothing coming out of the tower. Any help would be much appreciated

[jdl]

With the engine cranking, the two primary terminals at the coil, should have voltage? The primary terminals are the two small terminals. There should be a pulse on the negative terminal, with the engine cranking?

[gnemac]

Originally Posted by gnemac

91 5.2 dakota died on way home from work. Has not started since. Have replaced coil, distributor cap, rotor, pickup assembly in distributor. Checked wiring harness for bad splices they are all ok. This particular truck does not have a crank sensor on it. I have power going to coil but nothing coming out of the tower. Any help would be much appreciated

I have power on the positive side of the coil, on the negative side it stays lit it does not blink or pulse

[rhandwor]

You have a pickup in the distributor which fires the coil. If you used a 12volt test light and it doesn't blink when cranking on the coil neg. replace the pickup. If you remove the distributor use white out and make a mark where the rotor tip is on the dist. This makes it easier when putting back in.

[jdl]

My info seems to show, the ground side of the coil is controlled by the computer. Is there a hall switch in the distributor?

Were there any trouble codes?

[rhandwor]

The hall switch sends a signal to the dist.

[jdl]

Maybe I'm looking at the wrong diagram, but the signal from the hall switch goes to the computer.

The computer uses that signal for the rpm signal. The fact that there is voltage to the coil with the engine cranking, tells me, the computer does see an rpm signal.

Maybe I'm looking at the wrong diagram, it wouldn't be the first time.

[rhandwor]

I see a ref. pickup,6volt input,sensor return. The only way a coil will work on D.C. is if it is grounded monentarily. This is why the utility company uses A.C. voltage so then can use transformers. I just noticed you replaced the pickup.
Use a volt meter and check for the 6 volt input voltage to the pickup org. wire.
Use a volt meter and check for reference pulse you should get 1/2 voltage appx. 2.5volt. or use a logic probe.
Before I would try another pcm I would ohm the wires from the dist. to the pcm and from the pcm to the coil.
I would check the ground wires and fuses,and any relays.
The only the computer can fire the coil is if it gets reference so it knows what plug to fire. As it uses 3 wires it also monitors rpm.

[gnemac]

The error codes are code 34 and code42. I have changed the relays around in the black box but it did not make any difference

[jdl]

The diagram I was looking at shows the ground for the coil goes to the computer. The computer switches the coil ground.

If there is constant voltage on the coil ground with the engine cranking, the computer isn't switching the ground for some reason. If I'm looking for a signal on the coil ground, with the engine cranking, I look for an rpm signal, yes, a testlite should work.

It is my understanding that the computer will not ground the ASD relay unless it receives an rpm signal, the rpm signal comes from the hall switch. I need to add, when I look for a signal from the hall switch, I look for an rpm signal. One of the things that receives voltage from the ASD relay is the coil. The poster said that there was constant voltage to the coil primary terminals during the cranking cycle. That tells me, the computer does see a signal from the hall switch, if there was no signal from the hall switch, there would be no voltage to the coil during the cranking event. There is a prime circuit, with the key in the on position, no crank, there may be voltage at the coil for a second or two, but I discount that in this case, because I want to see an rpm signal, you have to crank it to get an rpm signal.

I AM UNDERSTANDING THE POSTER AS SAYING, THAT ALL DURING THE CRANKING EVENT, THERE IS VOLTAGE AT THE COIL.

As far as the codes, I'd erase those. Then give the engine a good crank and see if any codes come back? If one of the codes points to a relay, you have to check the relay circuits before suspecting the relay.

[rhandwor]

When you put the pickup in the distributor their is a rotor with eight tips. Sometimes you have to use a brass feeler gage and set the gap so they will work correctly. Were you very careful to put it in correctly. Did you remember to put the pin in the dist. gear. If you were able to install it without pulling the dist. check that it is rotating as some year dodges used a fibre gear and they have a habit of stripping out.

[jdl]

If there is a pick-up coil in the distributor, then there is no hall switch.

My info shows a hall switch, I guess I'm looking at the wrong info.

[rhandwor]

I think the hall switch is for the 4 cylinder not the 8 cylinder.

[gnemac]

When I replaced the pickup assembly(the part that looks like you turn it upside down and it is held in place with 2 screws) I did not have to pull the distributor. I did pull the distributor to check the gear on the bottom and it was ok. How do I go about erasing the codes? You guys are great in helping me to try and get this thing back on the road. Thanks

[rhandwor]

If you don't have a scan tool disconnecting the battery negative cable for 3 minutes should erase the codes.
Since you apparently have it running what did you find it might help somebody else.