Cleaned the check valve and no help either. However, finally found the problem. Crankshaft position sensor would not give a signal during start attempt, therefore the ECM would not turn on the VP-44. With no signal during crank, no codes were set because the ECM didn't know the engine was turning. Had taken it to Cummins Mid-South and they didn't have a clue and lightened my pocket book by $225 for nothing. Therefore I looked at the wiring diagrams and description in the repair manual and went straight to the sensor. $35 later it starts great.