Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1985 Chevrolet Impala 5.0 HFACTORY OEM SERVICE PROCEDURE
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.
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.