I have a 99 Sport, standard cab 3.9l w/5sp. It has 143k miles and has been relatively trouble free. About 2 months ago, it started to just stop. It turns over with no problem but won't start, like the fuel pump stopped working and 10 or 20 minutes later it would just start and run, like there was no problem. Since then, I have changed the fuel pump, removing and cleaning the tank, replaced the ignition switch on the column, replaced the rotor and dist cap (very needed) and, seemingly unrelated, the water pump/thermostat and next the belt tensioner (needed). I live in a heavy salt air environment and only use the truck twice a week. I start in the cooler morning, drive 15 mi and the truck is in the hot sun for 4-5 hours before the return trip where it invariably just stops. I set a timer for 10 minutes and it usually restarts, sometimes longer. it tends to do this 2-3 times during the 15 mile return trip but never first trip. To me, it is heat related but what causes the fuel not to be pumped? What shuts off that system? I have noticed a nobus in the odometer box and an amber check engine light. Allow me to add that I disconnected the horn wires when it just went off and was told about the expensive switch on the steering wheel. Any advice from the experienced??

 

I'm thinking PCM the computer or a wiring problem

Check the connections to the PCM look for an oil residue on the wires this is a problem that happens oil in the PCM connections

Un plug the battery pull each connection and Clean the PCM connections with the proper electrical cleaner spray see what happens


Like this stuff http://www.carkitsonline.com/product/?id=1117990 or this stuff http://www.all-spec.com/products/D5S...Fa1_QgoddywAzQ

Do you notice any weird running problems? like bucking weird idling

 

yep, what he said.

That the horn was going off on it's own AND the no-bus message, both separately big red flags, point directly to electronics problem.

 

Can you pull any problem codes?

 

While changing out the belt tensioner, I noticed the coil flaking apart and will replace it next. Thank You all for your input and I will try to get a code reader plugged in. There are no other outward signs of problems. In fact, with the parts that have been changed the DAK runs smooth and quiet. Will check the electrical connections on the PCM.

 

Coil flaking apart could be a problem

I will also ad have you pulled/replaced the sparkplugs?

If it is the coil that means the coil was getting cooked and that usually means a very wide sparkplug Gap.

But with your other problems I'm thinking you may have more than one problem