I own a 94 GMC with 265000 miles. The 6.5L is giving me problems. Can anyone help? It started out stalling going down the road. Then started to not start all the time. If you waited about 5 min or so and tried again it would usaully start up. Now it is not always starting after waiting and stalling out again after starting and not wanting to start up right away again. Is this a fuel problem or Electrical? It also runs a little rough at times.

Sounds like a PMD issue.
Can you give us more info about you truck or fill out the diagnostic list?

try this first start it and when it dies pull the fuel filter and see if it has enough fuel in it mine did same thing so i ran a toggle switch to my electric fuel pump on frame i turn it on before i start truck let it fill the filter up and leave it on till you shut engine off try this as a step to see if that is your problem it is not a permanent fix but it buys you time to figure out what is going on especially if you use truck daily.

Run the Diagnostic checklist and post the full results on here. Also update your signature so we know what you are working on!
Thanks,

That many miles,, could need injectors, have you replaced the fuel filter latley? Where is your PMD mounted, on the injection pump? Under what conditions does it "run a little rough"??

Look in the post above mine, and click on:
GM 6.5 FAQ's
6.5 Diag checklist
and Welcome new forum member.

these area's will point you to some info, that you need to read and then fill out
to answer some questions, So We can Help you out!! Also scroll up top to USERCP
go in there and Fill out a Sig. with info on your truck and any mods you might have done.
You WILL get help here but we need more info from you. :)

Welcome to the DieselPlace!!

Try pouring some room temp water over the IP when she is in a no start condition.........if she starts, It has been said IP is on it's way out.

That cools down the PMD, which is the problem. Probably NOT the IP itself going out, just that dang little black box gets too hot, and the transistors break contact with the circuit board.