Hi,I have 98 gmc 6.5td that randomly does not want to start at least once a day.Just got truck last winter. It probably sat for a while. Here is what I have done:replaced and relocated pmd, changed lift pump, replaced glow plug relay also put glow plug button in, replaced glow plugs, gave up.brought to diesel mechanic.they tested injection pump and replaced shut off solenoid. It started fine for them.Got truck back ran for few days then same deal. No start. Anyone have any suggestions?