Smart Relay Design for Fuel Pumps
Thought for 5 sec
I’ll create a new boosted-controller project brief and a Flux new-project link, keeping it separate from the existing relay design and focused on the 16 V / 25 A boosted architecture.
Worked for 1 min 54 sec
Work done
- Created a new separate Flux project: Automotive Smart Boosted Fuel Pump Controller 16V.
- Created a downloadable project brief: automotive-smart-boosted-fuel-pump-controller-16v-project-brief.md.
- Started an architecture thread in the new project: Boosted 16V Controller Architecture Plan.
Key architecture captured
- This is a 400 W-class boosted fuel pump controller, not a simple relay revision.
- Recommended mapping: FSCM 10 V = 10 V output, FSCM 14 V+ = 16 V output, linear between.
- Preserves: 0 V off, 10 V floor, 25 A pump current limit, thermal derating, red/blue LEDs, and 5-second buzzer.
- Adds: regulated boost stage, input-current limiting, boost overvoltage/regulation fault detection, and connector/thermal review.
Next steps
Open the new project thread and continue from the architecture plan. The first engineering decision is whether to use a single-phase or multiphase synchronous boost converter, because 16 V at 25 A is a ~400 W power stage.
Plan topology and parts
Compare boost topologies
Select controller IC
Define connector strategy
Create state machine
Run design review
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Ask about this doc
Test Plan Comprehensiveness Review and Walbro 525 Load Addendum
Summary
The existing J1 checklist, full relay validation plan, and test report template are a strong validation foundation, but they are not yet fully comprehensive for production-level signoff of the Automotive Smart Fuel Pump Controller. The main gap is that the plan needs a dedicated high-current fuel-pump load-emulation section using either a real pump, a programmable electronic load, or a motor/pump emulator that represents a Walbro 525-style load profile.
The official TI Automotive/Walbro F90000285 flow-curve data indicates that a Walbro 525/Hellcat-type pump can draw roughly 19 A around 40 psi at 13.5 V, rising toward approximately 25 A to 26 A at very high pressure. Therefore, the relay validation plan must explicitly test realistic pump operating points from approximately 15 A through 25 A, plus overload attempts above the controller's 25 A limit.
Comprehensiveness Assessment
What the current plans cover well
- J1 connector pinout and field-interface checks.
- Battery qualification and undervoltage behavior.
- Signal-following behavior across multiple FSCM analog command levels.
- Startup, shutdown, and brownout cases.
- Current limit and overcurrent behavior.
- Thermal derating and recovery behavior.
- Red/blue LED and 5-second buzzer fault behavior.
- Dynamic/transient metrics including rise time, overshoot, settling, and ripple.
- Environmental and mechanical validation categories.
- Test reporting structure.
What must be added for full relay validation
- Explicit Walbro 525-style high-current pump load simulation.
- Real pump validation, not only resistive/electronic load testing.
- Startup inrush characterization with realistic pump motor behavior.
- Back-pressure / fuel-pressure-equivalent current profiles.
- Long-duration thermal soak at 15 A, 20 A, and 25 A.
- Current-limit behavior above 25 A using a controlled overload profile.
- Pump open-load, locked-rotor, stalled pump, and intermittent harness tests.
- Supply droop during inrush and brownout recovery while the pump is running.
- EMI/noise observation during high-current PWM switching.
Required Load Simulation Strategy
Load types to use
Table
| Load type | Purpose | Required? |
|---|---|---|
| Programmable electronic load | Controlled DC current sweeps and repeatable limit testing | Yes |
| Real Walbro 525 / F90000285 or equivalent pump | Real motor inrush, commutation noise, hydraulic load behavior | Yes |
| Pump plus fluid loop or safe test fluid fixture | Realistic pressure/load curve validation | Strongly recommended |
| Motor emulator / inductive load | Repeatable PWM and transient stress without fuel handling | Recommended |
| Resistive load bank | Thermal and wiring stress baseline | Useful, but not sufficient alone |
Walbro 525-Style Load Points
Use the pump manufacturer's published flow/current data as the basis for test planning. For a Walbro 525 / TI Automotive F90000285-style pump, representative current draw is approximately:
Table
| Approximate operating condition | Expected current range | Test objective |
|---|---|---|
| Low pressure / free-flow region | 16 A to 18 A | Verify normal operation below heavy load |
| Typical EFI pressure around 40 psi | About 18.5 A to 19 A at 13.5 V | Validate common real-world operating point |
| Moderate high pressure 60 psi to 80 psi | About 20 A to 22 A | Validate sustained high-load operation |
| High pressure 90 psi to 110 psi | About 23 A to 25 A | Validate operation near controller limit |
| Extreme/high-pressure region | About 25 A to 26 A | Validate current limiting and derate response |
Additional Test Scenarios to Add
Pump load and signal-follow matrix
Table
| Test ID | Battery input | FSCM command | Pump/load condition | Expected behavior |
|---|---|---|---|---|
| WL-01 | 14.0 V | 0 V | Real pump connected | Pump off, no false start |
| WL-02 | 14.0 V | 1 V startup/prime command | Real pump connected | Soft-start/floor policy applies only if startup is qualified |
| WL-03 | 14.0 V | 10 V | Real pump at typical load | Pump output targets 10 V if current/thermal limits allow |
| WL-04 | 14.0 V | 12 V | Real pump at 40 psi equivalent | Output follows 12 V command |
| WL-05 | 14.0 V | 14 V | Real pump at 40 psi to 80 psi equivalent | Output follows/clamps to available battery |
| WL-06 | 14.0 V | 16 V | Real pump at high pressure | Output clamps to available battery ceiling |
| WL-07 | 11.9 V | 10 V | Real pump connected | Output inhibited, no 10 V floor synthesis |
| WL-08 | 14.0 V | falling 16 V to 10 V | Real pump connected | Output tracks downward smoothly |
| WL-09 | 14.0 V | noisy 0 V to 2 V | Real pump connected | No false startup or chatter |
| WL-10 | 14.0 V | valid command | Current forced above 25 A | Current limiting/derating asserts |
Pump motor transient tests
Table
| Test ID | Scenario | Measurement | Expected result |
|---|---|---|---|
| PM-01 | Cold pump startup | Inrush current, output voltage, gate waveform | No damaging surge or uncontrolled overshoot |
| PM-02 | Hot restart | Inrush and restart time | No latch-up or false fault |
| PM-03 | Rapid key cycling | Output state, fault flags | Predictable restart, no chatter |
| PM-04 | Pump disconnected while commanded | Output, current sense, red LED, buzzer | Open-load/dead-pump indication |
| PM-05 | Pump reconnected during command | Recovery behavior | Controlled recovery, no destructive transient |
| PM-06 | Stalled/locked rotor equivalent | Current limit and thermal response | Current constrained, fault/derate behavior active |
Thermal and endurance with Walbro 525-equivalent load
Table
| Test ID | Load point | Duration | Expected result |
|---|---|---|---|
| TE-01 | 15 A | 1 hour | Stable operation, no fault unless thermal threshold reached |
| TE-02 | 20 A | 1 hour | Stable operation, thermal trend recorded |
| TE-03 | 25 A | 30 minutes minimum | Current limit boundary verified, hotspot data recorded |
| TE-04 | 15 A to 25 A cycling | 2 to 4 hours | No intermittent failures, no connector heating issue |
| TE-05 | Real pump in enclosure | 4 to 8 hours | Validate real installed thermal behavior |
Fault indication validation under real pump load
Table
| Test ID | Fault condition | Audible alert | Visual indication | Expected behavior |
|---|---|---|---|---|
| FI-WL-01 | Undervoltage during pump operation | 5 seconds | Red fault pattern | Pump output inhibited/managed |
| FI-WL-02 | Open pump while commanded | 5 seconds | Red fault pattern | Dead/open-load indication |
| FI-WL-03 | Thermal derate while loaded | 5 seconds first event | Red thermal pattern, blue derated status if implemented | Output derates and recovers |
| FI-WL-04 | Overcurrent above 25 A | 5 seconds first event | Red current-limit pattern | Output constrained |
| FI-WL-05 | Persistent fault | Stops after 5 seconds | Red continues until clear | No continuous annoying alarm |
Key Measurements to Add
Table
| Measurement | Why it matters |
|---|---|
| Real pump inrush current | Confirms soft-start protects pump/controller |
| Current at 40 psi equivalent | Validates typical Walbro 525 operating point |
| Current at 60 psi to 80 psi equivalent | Validates high-load operation |
| Current at high-pressure/current-limit region | Confirms 25 A limit behavior |
| MOSFET temperature | Verifies power-stage thermal margin |
| Shunt temperature | Verifies R5 dissipation and layout |
| Connector temperature at J1 | Validates Deutsch DTP path and harness interface |
| Output voltage ripple | Checks PWM/control stability |
| FSCM input noise immunity | Confirms no false starts or chatter |
| Battery dip during pump startup | Verifies undervoltage behavior under inrush |
Conclusion
The existing test plans are good but should be treated as a baseline, not final DV/PV coverage. To fully test the relay across real use cases and edge cases, the validation set must explicitly include Walbro 525-style load emulation, real pump testing, pressure-equivalent load points, inrush characterization, and long-duration thermal validation at 15 A to 25 A.
Recommended Action
Update the existing full relay validation plan by adding a dedicated section titled:
"Walbro 525 / High-Current Fuel Pump Load Simulation and Real Pump Validation"
This section should include the load matrix, pump transient tests, endurance schedule, and real-pump fault behavior tests listed above.
Summary
Comprehensiveness Assessment
What the current plans cover well
What must be added for full relay validation
Required Load Simulation Strategy
Load types to use
Walbro 525-Style Load Points
Additional Test Scenarios to Add
Pump load and signal-follow matrix
Pump motor transient tests
Thermal and endurance with Walbro 525-equivalent load
Fault indication validation under real pump load
Key Measurements to Add
Conclusion
Recommended Action
