'99 3.9, it will occasionally (once a week or so) die on me, no pattern to it, sometimes just for a few seconds, sometimes long enough that it completely quits and wont start again for a good while. When it does this, I don't get a check engine light, no fault codes, everything appears completely normal, but the engine just cuts out. Doesn't make any sense. Any ideas?

New cap, rotor, plugs about a year ago. Probably not that.

 

Hows the fuel pump? Can you hear it turn on when this problem happens? When mine went out my truck just had no power and was barely running. Then it wouldnt start after I shut it off then later that day it started up and was fine but died again later that day.

 

I suspected the fuel pump, but I'm not sure how to check it. Just listen for it running?

 

When your problem happens listen for it. You can also check your fuel pressure it might show signs of being weak. Most garages will check it for free since it takes 5 min to do.

 

Check your computer connection at the firewall.That's what was wrong with mine,no more problems.

 

I would think that if it's the fuel pump it would bog down like it's running out of gas (which it is). If it just dies like turning off a switch, it sounds electrical.

 

Well it's in right now getting all new brake lines, but I didn't really want to ask the brake place to do troubleshooting like this. Now that y'all mention it, it doesn't bog down, it just quits. Ill start by re-racking all the computer connections and go from there.

 

Sounds like it may be a loose or corroided ground wire. Check and clean all the ground connections under the hood especially the one on the passenger side fender well.

 

I said firewall,I meant pass side fender.I put zip ties on my connectors cause i guess they were coming loose and the truck would die out.No more Problem truck runs great now.