Well.....if adjusting the timing does not work....Let's check voltage. Do you have a volt meter? Let the jeep cool down. Connect the volt meter to the battery, red (+) to positive and black (-) to negative on the battery. Record voltage. You will need a helper or if you have long enough leads to streach into the cab so you can see what happens. Start the jeep and record how much the voltage dips, it should return to 13-14 volts. Then turn the head lights on while watching the volt meter, it should dip and return to ~13-14 volts, record, turn the brights on and record, turn the heater motor on high and record. Now with all this running watch the meter, does the voltage stay at 13-14 volts steady or does it start to drop off. Watch for 5 minutes. Record your findings. Do you know the amp rating of your alternator?
Go for your 30 minute drive during the day without the lights or blower on. Come home leave the engine running, hook up your meter to the battery and watch the voltage, is it steady? Again turn the lights on, then the brights, then the blower in one minute increments. Record your findings.
Shut the engine off. Try and start and watch the voltage. Does it dip and how far. We are trying to isolate the problem. Alternator, Battery, Soenoid, Cables, Grounds. Thats assuming something mecanical is not binding up . Record each finding and and save for now. Write down observations.
post your results.
80 CJ7 5.0 Dual Exhaust, T176, D300, D30 w/ true trac, AMC 20 w/ ARB 4.56 gears, York OBA, Hydroboost