Fuel Drain Valve / Separator Drain Circuit or Mechanical Fault
Always verify drain valve operation and sealing when performing WIF drains or aeration diagnosis.
Fault Overview
Mechanical or circuit faults related to the water separator drain valve that prevent proper draining or allow continuous leakage or air entry.
Engine & Platform Coverage
Symptoms
- •Fuel drain valve stuck
- •Separator drain leak
- •WIF drain valve fault
- •Automatic drain fault
- •Drain valve causing aeration
Possible Causes
- 1.Stuck open or closed drain valve
- 2.Damaged drain valve O-ring
- 3.Automatic drain solenoid circuit fault
- 4.Debris blocking the valve
- 5.Cracked drain fitting
Wiring & Circuit Notes
If equipped with an electric or automatic drain, inspect the solenoid circuit for open, short, or voltage faults.
DVOM Specs & Sensor Tests
Visual operation of the drain. Electric drain solenoid resistance and voltage when commanded. Aeration test if the valve is suspected of leaking air on the suction side.
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
5 steps locked behind Technician Mode- 1Step 1 — Operate the Drain and Observe: Operate the drain and observe flow and sealing. Confirm the valve opens fully and seals completely when closed.
- 2Step 2 — Inspect for External Leakage or Damage: Inspect for external leakage or damage at the valve body and fitting.
- 3Step 3 — Test Electric Drain Solenoid: If equipped with an electric or automatic drain, measure solenoid voltage and resistance when commanded.
- 4Step 4 — Perform Aeration Test: Perform aeration test if suction-side leak is possible from the drain valve. Drain valves left partially open are a common source of aeration after servicing.
- 5Step 5 — Clean or Replace the Valve and Seals: Clean or replace the valve and seals. Verify the valve seals completely after service.
- 6Step 6 — Verify WIF Function After Service: Verify WIF function after service. Confirm the sensor reads correctly with the drain valve closed.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
Typical Repair Costs
Replace drain valve and seals $30–100; repair automatic drain circuit $50–150; clean debris $20–50. Total typical $30–180.
Start Diagnosing This Fault Now
AI Diesel Tech walks you through every evidence gate in the correct order. Choose the plan that fits your shop.
Related Systems
Related Fault Codes
Related Sensor Locations
AI Diesel Tech — The Technician's Diagnostic Engine
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Summary
Use the AI Diesel Tech diagnostic engine to run this code through a structured, evidence-gated sequence and get a confirmed root cause before any parts are replaced.