hello, was looking into a 95 GMC 3500. has 270k on the engine but has hd lot of engine work and suspension work. truck sounds maintained but is being retired. the seller mentioned tht it needs a new injector pump (mechanic told him)because it doesnt want to start sometimes when cold and also has trouble after 30-40mph. i was planning on possibly looking at the truck because its fairly cheap and clean. problem is that its about 45 mins away and i would have to drive it home if i decide to. the seller wasnt too specific what exactly it was doing at 30-40mph besides just "having trouble"
i work on cars for a living so i can spot a trans issue, but im not familiar with diesels. I have read through all the tests that i can do to make sure its a good engine and to determine other issues.
i am just wondering could the pump cause a similar issue? and are there any tests i could do to see if thats what it needs when i go to look at it this weekend? he mentioned something about the pmd still being under the manifold and mentioned that he was told its best to move them (says it gets worse when hot). i just need to know how i can determine the issue while im there, rather not buy a truck that needs a massive overhaul

 

If the PMD is still under the manifold you can pretty much count on it being bad as for the IP you wont know until you have a new PMD and a relocate kit.

 

Might help to have the timing set properly on the IP as well?
Air leaks in the fuel lines and lift pump issues also contribute to poor performance.
Oil pressure switches often fail and cause inoperable fuel lift pump issues since the IOPS powers the electric LP while the engine runs.
Look on youtube for LP relay jumping procedure to make the LP runs continuously while you test drive it to identify a LP power problem.