Fuel Injection System - Diesel: Testing: HPAA
- Remove the HPAA solenoid and, using compressed air, blow through the assembly first from the pump side and then from the outlet side. Air should flow in both directions. Remove the pressure regulator from the solenoid and see if the plunger is free. If the assembly fails either test, replace it.
- To test the solenoid, ground the housing using a jumper lead to the battery negative terminal. Attach another jumper lead to the same battery's positive post and connect this jumper to the solenoid lead terminal. The solenoid plunger should move inward with 12 volts applied and move fully back when jumper is disconnected.