New to diesels

[Meli]

Hi, new to this site and I am the owner of an inherited 99 GMC 2500 Suburban 6.5 turbo. When I got it it started dying while I was driving. Did some research with my son who is helping me with the truck and we figured pmd. So, I got a new black pmd (it had a grey one before), got it installed and it's not starting. It acts like it wants to but is just not happening. When I turn the key on I can hear the glow plugs come on and I wait for the little light to shut off but once it does it pops back on and just goes of and on like something may be up with the battery? Then I try to start and it'll turn over and act like it's going to start and then just dies. Any input will be appreciated - thanks.

[Yukon6.2]

I have the same Sub which was abandoned by the owner,who died a few years later.
He had spent a bunch of time trying to get it to run as well.Long convoluted story.
After i heard he had died his son called about it,i told him the bill owing on it prior to the death and he said keep it.
The catalytic converter was plugged solid,it would just start and die,once i undid the converter it fired up and ran great.This one had been driven till it couldn't run anymore. The soot the came out of the exhaust made a huge mess in my shop so do it outside.