Shut off while driving?

These trucks have problems with the fuel pump, but it can be the ignition module or a main power relay. When the engine stops running, we need to test for spark and see if the fuel pump is working. This can be done when you turn the key on without cranking the engine over, you should hear the fuel pump come on in the tank for about 5 seconds. If so, let's check for spark by checking out this video:

https://youtu.be/baq_aEWNQ0Y

This guide can help as well:

https://www.2carpros.com/articles/car-not-running-advanced

Please go over these guides and report back.

This truck has original low miles. It's had a new fuel pump, pump relay, new throttle body fuel injectors, new ignition module, cap, and rotor. When driving before Christmas, it stalled out. I was able to re-start it after about 10 minutes and drive home. Backing into the garage and idling for 5 minutes, all seemed fine. My latest test was to run it at idle for 1 and 1/2 hours whereby it didn't stall but my idle did not drop down as normal. Also, my temperature gauge stayed low when it should have been higher. It has a larger 'Be -Cool' brand radiator which could be somewhat of a factor, but the outdoor temperature was about 65 degrees. Could any of this factor in my problem, or what could it be?

Wow those are low miles I thought you were kidding in the first post, sweet truck. Old/bad gas comes to mind in a truck this old and not being driven. Did you flush the fuel tank when you replaced the fuel pump?

Let's run the codes to see what comes up, here is a guide to help:

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

Also, when it will not start can you depress the throttle pedal to see if that makes a difference, please?

Hi Ken, yes, the fuel tank was completely drained and rinsed with fresh gas, then drained again before the new fuel pump. Then re-installed and filled with fresh gas. There are no codes in the system except the code 12 which is system normal. I want to add that this truck has an aftermarket distributor from Jeg's Perf. It's very similar to the stock unit. Also has an MSD Digital Multi Spark box and coil. There's a pilot on the MSD box which stays lit when the engine is running. During that 1- and 1/2-hour idle test it was fine. The ignition module is a new AC Delco part. I 've heard some of these can go bad even when new. During that idle test I raced the engine up to near 3,000 RPMs and let off with no problems, but I am baffled as to why my idle didn't settle down and the temperature gauge stayed low. No overheating either. Hope all that helps.

I would remove the MSD Digital Multi Spark box and coil and replace it with stock parts, we have no way of knowing what's going on with aftermarket parts. I would check RockAuto.com for an ACDelco rebuilt distributor with new coil. here is how to install it. Also check the TBI base gasket. Check out the images (below). Please let us know what happens.

Hi Ken, your thoughts of returning to the OEM ignition system is fine and a thought of my own as well. However, by doing that (removing MSD, after market distributor and coil) you'd just be eliminating those parts as the possible cause yet not knowing absolutely if they were. All these parts were on the truck when it cut out. Then after a short period I was able to restart and drive on. Now as I said, my latest test was to run at idle for an hour and a half, and it did not cut out. In my opinion, you really have to run and test with everything intact as was the day it stalled to see if it'd do it again. I can bypass the MSD box very simply by disconnecting from the battery and changing coil connections. That would rule that out. The MSD coil has been on for quite a few years without a problem but can always be a first time. I believe it's something that heated, maybe shorted, then cooled and returned to function again as would a breaker or something. Another test would be to drive it so it's under load, but what if it cuts out and does not restart? Then I'm stuck and need a flatbed so it's hard. I live off a busy main road and not a sub-division where I'd be able to cruise around the block and push it back if it quit. Getting a friend to follow may help, but still not the ultimate solution either. Thank you!

When the engine stalls shut the key off then back on again without cranking the engine over to see if you can hear the fuel pump come on in the fuel tank for about 5 seconds, if so, let's check for spark to help see which system shut down which can help us see what system is failing.

https://youtu.be/baq_aEWNQ0Y

Please go over this guide and report back.