SPN 1347 FMI 5 — Fuel Pump / Fuel Delivery Control Circuit Open
Fuel delivery control open is an electrical command-path diagnosis first. No-start after pump connector left unplugged and intermittent open at relay bases are the most documented patterns. The FSM enforces command-and-power proof before pump replacement.
Fault Overview
SPN 1347 FMI 5 is a fuel pump or fuel delivery control circuit open or low-current class fault depending on OEM mapping. Open control wire, failed relay coil, blown fuse, unplugged pump connector, and failed pump motor open are the primary causes. No-start after pump connector left unplugged and intermittent open at relay bases are documented patterns. Replacing the supply pump before verifying command voltage and power feed is the most documented misdiagnosis pattern.
Engine & Platform Coverage
Symptoms
- •Fuel pump circuit open
- •Lift pump not running
- •Fuel delivery control open
- •No-start fuel pump electrical
- •Hard start after filter service
Possible Causes
- 1.Open control wire — open control wire producing no command path to pump
- 2.Failed relay coil — failed relay coil producing no pump command
- 3.Blown fuse — blown fuse producing no power to pump circuit
- 4.Unplugged pump connector — unplugged pump connector producing open circuit
- 5.Failed pump motor open — failed pump motor internal open producing open circuit
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
4 steps locked behind Technician Mode- 1Step 1 — Verify Command Present: Verify command voltage is present during key-on, prime, and run events. No-start after pump connector left unplugged is a documented pattern — always inspect the pump connector and circuit after any recent filter service. Confirm the ECM is commanding the pump.
- 2Step 2 — Check Fuse and Relay Feed: Check the fuse and relay feed. Inspect the pump connector, relay base, fuse and junction power feeds, and ground studs. A blown fuse or failed relay coil producing no pump command requires fuse or relay replacement.
- 3Step 3 — Voltage at Pump Under Command: Measure voltage at the pump under command. Confirm command voltage is present at the pump connector during key-on prime. A voltage fault at the pump under command confirms a power feed or relay fault.
- 4Step 4 — Ground Integrity: Verify ground integrity at the pump circuit. A ground fault producing no pump operation requires ground circuit repair. Measure voltage drop on the pump ground circuit.
- 5Step 5 — Pump Replace Only If Power and Ground Are Good: Replace the pump only if power and ground are confirmed good. A pump replaced without power and ground proof may replace a good pump into a circuit fault that will fail the new pump.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
1 steps locked- 1Replace relay or fuse if relay or fuse fault is confirmed.
- 2Repair harness if open circuit is confirmed.
- 3Replace supply pump if power and ground are confirmed good and pump fails ($150–$600+ typical).
Unlock full diagnostic steps, DVOM tests, and repair procedures.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
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.
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Summary
Fuel delivery control open is an electrical command-path diagnosis first. The AI Diesel Tech FSM enforces command-and-power proof before pump replacement.