i have a 1990 D250 12 valve cummins and i was wanting to turn my injection pump up a little but i cant get the darn screws off that hold the star wheel cover on. im afraid ill end up breaking the heads off the screws. theyve never been taken off. any tips or tricks on getting them off?

 

Vice grip the heck out of them and then go to Home Depot and get Allen head screws for it or 10mm bolts.

 

if this is the part, then here's what i would do, with a small punch smack each screw on the head pretty hard !
that should do it, you will be surprised on how well it works!!!!!!
http://landroverfaq.com/albums/VE/pompe.jpg

 

I've done something similar to John, I used a long, thin bar to get to mine (3rd gen vs 2nd gen) and hit them with a hammer on all sides- I hit the bar while it was on the side of the screw. This breaks the bond between the screw and the housing.

Good luck, this gave me a lot of hate until I got them out. Twisted a good handful of T25s too...