Somebody I know has a 96 6.5 turbo with hard starting problems.It cranks for a while then starts but runs rough,push on the accelerator pedal and it smooths out.cold or hot same thing. At Highway speeds it stumbles.He says driver changed few months ago.Would it be the pump or something else?

Need to know if there are any codes involved first. Check lift pump operation. Make sure you have a clean fuel filter.

New PMD pump mounted, or remote mounted? If remote mounted, is it above the manifold or a REAL remote away from engine heat?

There are some hard start tips to check in FAQs as well as how to check for codes

did not say about any codes.He did change IP(used) and used same driver on it.Would a bad lift pump cause these symptoms:(hard starting,rough idle till accellerator pushed,bucking on highway,black smoke)?He insists the driver is good.Mechanics told him it is the pump.Since he swapped pumps with a used one what are the chances of the used pump having the same symptoms?Oh yea the driver is pump mounted.

Hit the FAQs and do trouble shooting there 1st let us know what you find out and we will go further, owning a 6.5 will require some effort on your part, it's simple and complex at same time, we can shotgun you a list of possibilites and guess wrong, a wrong guess can cost you big bucks so do yourself & us a favor and try FAQs suggestions 1st. Dealer screwed a member in this thread http://www.dieselplace.com/forum/showthread.php?t=38475 by guessing at a problem rather than doing step by step trouble shooting efforet, which starts with reading diagnostic codes then proceding, how to read codes is also in FAQs. You are an OBD I truck by the way

Thanks TD.I told the guy to check the driver on injection pump and if the lift pump is working.When I hear from him I will post his results.He is hell bent on it beeing the IP though.We wiil see!!

Invite your buddy to stop by here for a visit, PMD often can be the problem, but lots of preliminary troubleshooting required 1st before swapping out PMD