YJ computer problem
madtom
Jeeper
Ran power to temp gauge, motor shut off, now no spark... what did I fry?
YJ computer problem
- Thread starter madtom
- Start date
BusaDave9
Always Off-Roading Jeeper
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- Durango, Crawlarado
- Vehicle(s)
- 1979 Jeep CJ5 with 304 V8, T18 Transmission, Dana 20 Transfer case with TeraLow 3:1 gears, 4.88 axle gears, Detroit Locker up front and Ox Locker in back with 1 piece axle shafts, 36" SuperSwamper SX Tires, Shackle reversal, MileMarker Hydraulic winch, MSD 6A ignition.
A dash mounted electrical temp gauge should simply measure the resistance of the temp sensor in the engine. If that stopped your engine I guess you must have created a short. I assume you removed the gauge and the engine sill didn't start. This gauge should use the switched power that comes on only as the ignition switch is turned on. What else is not working? Does the radio and the rest of the accessories still work? First place to look is the fuses.
madtom
Jeeper
the gauge never did work. It is a dash mounted unit, but it is powered by the factory plastic circuit board because it is a 94. Checked all the fuses, still no spark. Is it possible that the power that I ran into the gauge wire backfed into the computer?
BusaDave9
Always Off-Roading Jeeper
- Posts
- 8,244
- Thanks
- 81
- Location
- Durango, Crawlarado
- Vehicle(s)
- 1979 Jeep CJ5 with 304 V8, T18 Transmission, Dana 20 Transfer case with TeraLow 3:1 gears, 4.88 axle gears, Detroit Locker up front and Ox Locker in back with 1 piece axle shafts, 36" SuperSwamper SX Tires, Shackle reversal, MileMarker Hydraulic winch, MSD 6A ignition.
It's too soon to say its the computer.
Check the voltage on the coil. Not counting the big ignition wire going to the center of the distributor there should be 2 wires going to the coil. One should be marked "+". This should have 12 volts (or at least 8) when the ignition key is on. If this voltage is good then the problem is on the trigger side of the coil. The other wire on the coil may be marked with a "-". This is the trigger side. It should get pulses telling the coil when to make voltage for the spark. This side of the coil should have at least 6 volts as you are cranking the engine. If you don't have 6 volts here then your problem may be the pickup assembly or the computer. The computer give these pulses to the coil but it need the pickup assembly in the distributor to sense the rotating engine. If the pickup assembly is bad you will never get a spark.
Check the voltage on the coil. Not counting the big ignition wire going to the center of the distributor there should be 2 wires going to the coil. One should be marked "+". This should have 12 volts (or at least 8) when the ignition key is on. If this voltage is good then the problem is on the trigger side of the coil. The other wire on the coil may be marked with a "-". This is the trigger side. It should get pulses telling the coil when to make voltage for the spark. This side of the coil should have at least 6 volts as you are cranking the engine. If you don't have 6 volts here then your problem may be the pickup assembly or the computer. The computer give these pulses to the coil but it need the pickup assembly in the distributor to sense the rotating engine. If the pickup assembly is bad you will never get a spark.