Mack DM stalling (fuel problem?)

[Lucky dogg]

I have a 1995 mack DM.  It is an oil and gas service rig.  The mack motor runs the service unit body also.  Recently, I sent the mack to a local mack garage bc it had a loss of power and was stalling.  They told me it was the charge air cooler and fixed the air compressor unload valves.  This did not solve the issue and they had it over a week.  The truck starts and runs.  It idles fine, does not have a miss, and the service unit seemed fine also.  We drive it down the road and it acts like its out of fuel and stalls.  It takes several cranks to get it back started also.  As time progresses it is getting worse and worse.  I had the crew do the normal (changed fuel filters, air filter, check battery cables, checked fuel tank cap, pick up tube in tank, ect).  We need this rig to run bc unlike a normal semi, my 3 guys who work on the rig daily go with out a check when its broke.  It is an econodyn.  Fuel linkages are manual and does not appear to have a computer on the frame.  Please help as we are not sending it back to mack unless it is absolutely necessary.  Thanks all!