This might not be the right forum to post this question but I thought maybe someone might be able to help me out. My wife's 96 Voyager 3.0 liter quit running while driving down the road the other day, after a 15 minute cool down it started and made it about 1/2 mile and shutdown again. The coil wasn't throwing any spark so I thought it was probably a coil going bad or a pickup in the distributor so I swapped them out and still had the same problem with it shutting down during a drive. Setting still the thing will idle fine for any length of time without stopping so I figured maybe there's a wiring harness problem and with movement a circuit opens up. So with the engine running a grabbed the rear harness and moved it around which caused an intermitten cutout. OK, so now I thought all I need to do is open up this harness and find out what wire is damaged. Now I've got the harness opened up from the area behind the engine to the underhood fuse box and can't find anything wrong. With a testlight I'm not getting any power going to the coil other than a brief flash when the key turns to the on position, nothing in the run position and nothing in the crank position. Now I'm starting to second guess the wiring harness problem and think it may be a computer problem or a connection at that end of the harness. There's a whole lotta wires in that harness. Any suggestions? Fuses are all good and I've swapped relays around to verify it wasn't a bad relay. Should there be power going to the coil with the key in the run position? Does the computer control the power to the coil? I might have it scanned but I don't think it's going to pinpoint the problem. Any help or troubleshooting ideas would be greatly appreciated. Bob

Doc here,

FIRST off, USE a DVOM...not a test lamp..a lamp won't show computerized voltages..or any thing much less than 12 volts..Computer signals are 5 volts or less and are not hard grounded.

Check the automatic shut down relay, substitute it for a known good relay.

Check the module, it may be thermal..according to the schematic it looks to be part of the distributer / Coil assembly on the 3.0.

Do a code check.

Doc

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Thanks Doc! I got her up and running again today, crank sensor was bad. I didn't realize this model had a crank sensor since I seen a pickup in the distributor but was told that was only for cam timing. Runs like million bucks again. The scan tool wouldn't pickup the defective sensor.

'96 Dodge may use an 8 volt refrence

you would need a lab scope or an osciliscope to diagnose that. common problem with Mopar's, is the no start/ crank sensor condition. reason is, ignition will not spark until a crank signal is detected. no signal, no spark

Doc here,

The internal buss system on a computer is + and - 5 volts for signal/Buffer, and + and - 12 volts for power to the mother board. The buffer/Drivers run off a industry standard - 5 volt regulator as well as the ROM/RAM/MPU/Serial buss system. CMOS/HMOS Architecture is designed industry wide to run at these voltages, with a small window of margin.

The way to tell for sure is pull the computer cover, and on one or the other sides of the case will exist a heat sink with 3 or more 3 tab regulators affixed to it. look at the last 2 digits of the regulators, that will tell you the voltage, If it is an 05 , it is 5 volt (+ or - ) regulator, if it is a 12, it is a 12 volt + or _ regulator. These power the buffer/Drivers for the sensory input from the real world, and convert it into terms the serial buss can deal with.


GM COMPUTER

Doc

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Doc here,

Crank sensors are usually the #2 problem after a module on spark loss..I test the module first because it's easy to get at..

To test the Crank sensor, use a DVOM set to R X 1, calibrated to "000", across the plug and pass a simple magnet over it..if it is working, it will "Jump" on the meter scale every time the magnet passes over the switch..

All the crank sender is , is a simple SPST switch that opens or closes every time a magnet passes in front of it..the magnet pulls (or pushes) a mechanical devise that in turn activates the switch. The switch contacts usually burn out on these.

Doc

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yes i kno industry standard is 5v refrence, but there are some vehicles made by mopar that use an 8 volt refrence, obd 11 may not use it, idk but I did diagnose a crank sensor on a '95 jeep with a 2.5 4cyl, the sensor had 8 volt refrence (and dvom was reading 8 volt, but no change= bad sensor ), as the manual said it did. it was a no start condition. sensor fixed it.

most newer chrysler vehicles use a 8 volts ref. voltage on crank and cam signals

Doc here,

From the 1996 Plymouth Voyager Manual:



I have REBUILT many of these GM and Other computers AT the motherboard COMPONENT level for years..basic architecture (The CHIP-SET ) is based on a +/- 5 Volt buss, The Serial buss is based upon the window of a -5, +5 Voltage as well as the quad drivers..(they Drive the sensors, and provide buffering to the address lines of the computer buss.) I/O.

Mopar May have an 8 volt system in some of the newer vehicles out..Since I don't rebuild too awful many Mopar computers per annum, I can honestly say I have YET to run across one..OF the MOPAR computers I have rebuilt, They have all been 5 volt buss..If they are running 8 volt architecture in new models, this might be a proprietary Chip-set and sensors..AND are probably Way more expensive to repair/replace (the only game in town.) than it's predecessors.

Doc

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as far as i have seen in the field ,,chrysler and jeep are the only ones using 8 volts for cam and crank sensors. all other sensors on chrysler vehicles are 5 volts.

5 volt ref. crank works hard consedering the location 96 regal same problem fixed it

yeah, I don't know which years or which models of chrysler/ jeep use the 8 volt refrence, but I know on a 1995 Wrangler 2.5l 4cyl, the CKP sensor uses an 8 volt refrence. the throttle position sensor was 5v refrence.