I'll try to cover several related bases here:
1. the lack of a MIL/CEL light does not mean there are no codes stored; it just means any stored codes are likely not critical (ex. if you pull your viscous heater relay a relay open code is stored but it does not trigger the MIL light)
2. codes are stored until they are cleared. Codes are cleared by a code reader with the delete code function OR codes may clear on their own if the reason for the code goes away (ex. if your torque converter leaks down due to the filter problem mentioned and you crank up, shift into gear and drive away as soon as the transmission "clunks" into gear you will get about 150' at which point there is a significant engine/transmission shudder and the engine stalls often with a MIL; that MIL will clear if you complete like 3 more starts without the stall problem).
3. the temporary fix to torque converter leak down after the KJ has been sitting for ca. 8hrs is to crank up, shift into neutral (no fluid is pumped in park), bring the idle up to 1,000rpm for like 10 seconds, drop idle back to normal, shift into gear and drive like normal. The long term fix is to service the transmission (be sure to use ATF+4) and replace both filters (I favor WIX - whatever you do don't buy any OEM filters over ebay or other such non-dealer web site). NOTE: even filters with a good check valve can get to the point where the check valve no longer works properly. FYI if you are at 80K and it's been more than 50K since the TC fix was done then you are overdue for tranny service which IMHO should be done every 50K. Bottom line is if your #3 failure to engage occures at first crankup after the KJ has been sitting for a while then service the tranny. Any dealer with 1/2 a brain should have done that when you took it in as there is a TSB out on this intermittent problem which Chrysler products have had for decades.
4. items 1 and 2 sound fuel related and the starting point for those problems is the fuel head/filter. If you have the 1st gen OEM filter head it needs to be replace IMMEDIATELY regardless of whether or not it's the cause of these problems as the fuel heater element on the 1st gen head is very prone to burning out and leaking fuel. On the 1st gen fuel head the 2 electric plugs toward the top of the head are of noticably different sizes (one on the driver side, heater plug, is smaller) as opposed to the 2nd gen head where the plugs are the same size and the heater one typically is blue (see
http://www.greendieselengineering.com/f ... st/76.page). Shop around a bit for the 2n gen head and wiring pigtail as prices vary (Steve White had a decent price not too long ago) and be aware that the new head comes with a new filter installed.
See my post about 2/3rds of the way down the page at
viewtopic.php?f=5&t=60953&p=676662&hilit=fuel#p676662 for how to change out the filter head. It's no big deal to do yourself.