Fuel Tank Pickup Restriction / Suction Side Restriction Diagnosis
When filters and lift pump are proven good but supply pressure remains low, test with an external fuel source and inspect the tank pickup.
Fault Overview
Diagnosis of restriction on the tank pickup or suction side that produces low supply pressure, aeration, or lift-pump overload even when filters are clean.
Engine & Platform Coverage
Symptoms
- •Tank pickup restricted
- •Fuel tank suction restriction
- •Low pressure with clean filters
- •Pickup tube clogged
- •Tank screen blocked
- •Lift pump overloaded
Possible Causes
- 1.Clogged tank pickup screen
- 2.Collapsed or kinked suction line
- 3.Debris in tank
- 4.Failed check valve in pickup
- 5.Incorrect tank sender/pickup assembly
- 6.Wax or contamination buildup
Wiring & Circuit Notes
Not primary. Confirm lift pump electrical performance first so the pump is not falsely condemned.
DVOM Specs & Sensor Tests
Supply pressure remains low despite new filters and a known-good pump. Vacuum gauge on the suction side may show excessive vacuum. Inspection of the pickup screen after tank access.
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 — Confirm Filters and Lift Pump Are Good: Confirm filters are new and lift pump electrical/pressure capability is good. The tank pickup is suspected only after these are proven.
- 2Step 2 — External Supply Test: Measure supply pressure and note if it improves with a known-good external fuel source connected to the inlet. Improvement confirms the restriction is in the tank or suction line.
- 3Step 3 — Check for Excessive Vacuum on Suction Side: Check for excessive vacuum on the suction side with a vacuum gauge. High vacuum confirms restriction upstream of the lift pump.
- 4Step 4 — Inspect Visible Suction Lines: Inspect visible suction lines for kinks or collapse. Flexible lines can collapse under high vacuum.
- 5Step 5 — Access and Inspect Tank Pickup Screen and Tube: Access and inspect tank pickup screen and tube. Running the tank low repeatedly allows debris concentration at the pickup.
- 6Step 6 — Clean or Replace Pickup Assembly: Clean or replace pickup assembly as required. Retest pressure and aeration after repair.
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
Clean or replace tank pickup $150–400; repair or replace suction line $100–250; tank cleaning if heavy contamination $300–700. Total typical $150–700 depending on tank access.
Start Diagnosing This Fault Now
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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.