94 3.0 caravan, no spark, no codes

[jerrydc]

No output from the coil. Coil primary is 12v at key on and crank, but immediately drops off to 0. No codes present from key on and off. The coil primary wire is good back to the computer, so it's not the harness. Is there any other possibility other than the computer? It was running fine and just quit rolling down the road. Thanks for any suggestions. jerrydc

[Stevo2]

Originally Posted by jerrydc

No output from the coil. Coil primary is 12v at key on and crank, but immediately drops off to 0. No codes present from key on and off. The coil primary wire is good back to the computer, so it's not the harness. Is there any other possibility other than the computer? It was running fine and just quit rolling down the road. Thanks for any suggestions. jerrydc

Bad Crankshaft or Camshaft Position Sensor?

[jerrydc]

No cam or crankshaft sensors on th 3.0, and they should set a code if there was.

[moparman58]

You might want to search the threads for coil problems. Vaguely remember reading about a wire that runs to the coil that goes under the air box and chafes, eventually grounding out. Sorry I don't remember better, but the little grey cells don't work so great any more and I haven't had that particular problem.

[jerrydc]

tHE WIRES TO THE COIL ARE FINE. Someone else has suggested the ASD rely or the optical sensor in the distributer. The rely was fine but I'm still checking the sensor.
Thanks.

[Stevo2]

Originally Posted by jerrydc

No cam or crankshaft sensors on th 3.0, and they should set a code if there was.

The optical sensor may go bad and not set a code. The computer does not always set a code when something is wrong. We that have been in the business for a while refer to the sensor in general terms of Cam or Crank Sensor.

Now, pull the negative battery cable off to allow the codes to clear, try to restart and check and see if a Code 11 comes up. If it does, the Cam/Crank/Optical/Hall Effect/etc. sensor is bad.

Code 11 will NOT set unless you properly clear all error codes. This is a hidden feature of Chryslers computer. One that most people don't understand because it doesn't make any real sense. Once the computer stores the first pulse in memory it will never look to store the pulse again. The computer will however shut the ASD relay down if it does not see a pulse from the sensor. Once you completely clear memory the computer will once again look to store the pulse, if it sees it, it gets stored...if it does not see it, it posts a Code 11.

Code 11* No crank reference signal No distributor reference signal detected during engine cranking.

* Malfunction Indicator Lamp (MIL), (previously called the Check Engine Lamp), will not be illuminated at all times when this Diagnostic Trouble Code (DTC) is set. Cycle ignition key or use scan tool to access trouble code. SEE HOW TO EXTRACT DIAGNOSTIC TROUBLE CODES .

Sensor Description and Operation

LOCATION

Housed in distributor.

PURPOSE

The Powertrain Control Module (PCM) uses this input to determine engine speed and crankshaft position, and adjusts ignition timing, fuel injection, and idle speed accordingly.

OPERATION

Pick-up generates pulses when slots pass between Light Emitting Diodes (LED's) and photo diodes.

THEORY

A disk, with 2 sets of slots, spins at half engine speed, between two LED/photo diode pairs (optical sensors).

The outer or "high data rate", slots pass through the corresponding sensor at a rate of 1 slot per 2 degrees of crankshaft rotation.

The inner, or "low data rate", set of 6 slots, correspond to top-dead-center for each piston.

The "high data rate" signal is used to control ignition timing for engine speeds up to 1200 RPM, because during cranking and at idle, engine speed changes with the firing pulse of each cylinder.

Above 1200 rpm, speed changes due to individual firing pulses are negligible. Therefore the "Low data rate" slots are used to time fuel injection and ignition at engine speeds above 1200 RPM.

If the PCM does not detect input from the pick-up, the PCM de-activates the ASD and fuel pump relays, interrupting power to the fuel pump, injectors, coil, and oxygen sensor heater, preventing fuel injection and ignition, (a no start condition).

[jerrydc]

I found the problem when I was checking into the optical sensor. The distributer shaft sheared. This engine was from a salvage yard and only had a few miles on it since being installed. when it sheared. Unfortunately the base of the distributer also broke off in the block, a real pain to remove. The next challenge, once I get it all out will be properly timing the replacement distributer.