looking for some help here. I inherited my fathers 1986 f-250 with 6.9 i.d.i., I have been having what I think is an air intrusion problem. I put a new injector seal kit with the new o rings and plastic cups on top of injectors that carry return fuel to tank because I knot iced d a couple wear a little damp looking. I bled the lines got it running, seems to run great drove for about 30 miles ran good nothing unusual put in garage, tried to restart a couple hours later and same problem, starts runs for about 10 seconds and shuts down, if I rebleed lines and fill filter it will run fine again until shut off then won’t start again or run for afew seconds and die. I put a piece of plastic tubing from last injector on drivers that goes back to tank and another piece fromfirst injector front pass. Side to filter housing,I watch the tubing at idle I don’t see any air bubbles, if I run up on fast idle I can see some very small air bubles in the line to the filter thats all.
I also notice if I push the staiter valve in after cranking to bleed it don’t seem to have much pressure there, how much should I have?
little back round on truck 86 dad was original owner has only 65,000 miles has had excellent care all it’s life, just a lot of seal type issues from sitting a lot of it’s life
been thinking about bypassing old manual lift pump with an electrical pump tank and old lft pump, can I stub off lines from old pump and just leave it on block, or do I need to make a blockoff plate and completely remove it?
Any help is appreciated
thanks

If the diafram has a crack in it, will it be able to keep up the injection pump when its running?
I did buy the Mr gasket pump so I’m glad you said that.
I will go that route, I just wasn’t looking forward to changing the stock pump looks likeit could be a real pain to get that rear bolt guess I’ll hope for the best.
dad would’ve wanted it stock anyway
Thanks again