Excessive Cranking Fuel Pressure / Difficult Starting Hot The hard starting problem is caused by a Bosch VP44 injection pump with a damaged diaphragm internally. A torn diaphragm is typically caused from a Bosch VP44 injection pump that was operated at below 10 PSI for an extended period of time. So technically you should replace the Bosch VP44 injection pump to repair the damaged diaphragm but most rig up an oil pressure switch or a starter delay relay.