If your car suddenly died with no fuel, no boost, and now won’t turn over, here’s a quick diagnostic breakdown you can follow, especially considering your setup on Project Black Pearl (2005 WRX with VF22 turbo and custom mods):
🧠 Top Potential Causes Based on Symptoms
- Fuel System Failure
Symptoms: Sputtering, no gas delivery.
Check:
Is the fuel pump priming? (Key to ON, listen for 2–3 second hum)
Could the Walbro 255 pump be disconnected, blown fuse, or dead?
Any loose connections or clogged fuel filter?
- Ignition/Electrical Issue
Symptoms: No spark, engine won’t turn over.
Check:
Battery: Fully dead battery = no crank. Try jump-starting.
Main grounds: Check engine bay grounding points and battery cables.
Check for blown main relay or fuel pump relay.
If you have coil pack conversion: check ignition harness plug.
- Timing Belt Failure (Catastrophic)
Symptoms: Sputter → stall → won’t turn over properly (or sounds weird).
Check:
Listen during crank: If it spins very freely or too fast = no compression.
Remove a timing cover bolt and peek at the belt if visible.
If it’s snapped, DO NOT keep cranking — risk of valve damage.
- ECU or Tune-related Fail
Symptoms: Car dies suddenly with no warning, won’t crank, electrical seems dead.
Check:
Verify no ROM corruption or flash failure if recently tuned (especially via Tactrix).
Any grounding faults or short circuits near ECU?
- Boost Hose / Vacuum Line Catastrophe
Symptoms: Might cause stalling but shouldn’t prevent crank.
Check:
If the turbo inlet collapsed (cheap ones can do this) — inspect for blockage.
Boost leak alone doesn’t usually prevent cranking, but can cause sudden loss of power.
🔧 Quick Action Plan
Step Task Tool Needed
1 Check battery voltage Multimeter
2 Listen for fuel pump Ear / scan tool
3 Check CEL / ECU light on key ON Dash indicators
4 Attempt OBD2 scan Tactrix / ELM327
5 Check fuses (under dash and hood) Visual / fuse puller
6 Pull a spark plug and check for spark/fuel smell Spark plug socket
7 Check oil cap area for visible timing belt tension Flashlight
🔥 Critical Alert
If engine cranks extremely fast or sounds “whirry” without the usual compression strokes:
STOP cranking.
May be timing belt failure. Compression test or visual inspection needed before further attempts.
📋 Log It
Document:
Last known running state
All mods installed (especially anything in last 1–2 weeks)
Weather and temperature
When it last had fuel, oil, or service
Would you like a diagnostic checklist sheet or mobile-friendly version to print or store in your glovebox/phone?
Let me know how far you get, and I can help isolate it further with more detail from your findings.
Absolutely — here’s the continuation of the rapid fuel starvation diagnosis, specifically tailored for your 2005 WRX Project Black Pearl:
🔌 1. Direct Fuel Pump Power Test (Confirm Pump Function)
If you haven’t already done this, here’s how:
✅ From Rear Seat Access:
- Remove the rear seat bottom (lift from front edge).
- Unscrew the fuel pump access panel (driver side).
- Expose the fuel pump harness.
- Use a fused jumper wire from the battery:
- Connect 12V to the pump power pin (often white/black or red)
- Ground to chassis or black wire
- Listen closely — the pump should hum immediately.
| Result | Meaning |
|---|---|
| ✅ Pump hums | Pump is functional. Problem is ECU signal or relay wiring. |
| ❌ No sound | Fuel pump is dead OR ground/power circuit is open. |
⚠️ 2. If Pump Only Runs When Jumped
Then the ECU is not commanding the pump, which happens in only a few cases:
| Root Cause | Effect |
|---|---|
| 🟥 Crank Position Sensor failed or unplugged | ECU doesn’t detect engine movement = no spark, no fuel |
| 🟥 ECU in fail-safe (oil starvation logic) | Some ROMs or base maps cut fuel/spark if oil pressure = 0 |
| 🟥 Relay not getting 12V trigger | Starter signal path, main relay, or ignition source failure |
| 🟥 Blown fuel pump fuse or faulty relay | No power to pump, even if ECU wants to send it |
🔎 3. Confirm Crank Signal (ECU Sees RPM)
Use Tactrix + RomRaider logger or any OBD2 app (Torque Pro, etc).
Watch RPM while cranking:
| Result | Meaning |
|---|---|
| ✅ RPM rises while cranking (even 100–200) | Crank signal good — ECU knows engine is spinning |
| ❌ RPM = 0 during crank | CKP sensor failure — the ECU doesn’t trigger fuel/spark |
This is the single biggest trigger of fuel starvation with an otherwise healthy system.
🧰 What To Do Based on Test Results
| Symptom | Fix |
|---|---|
| Pump works when jumped, not via key | ✅ Replace or re-seat crank sensor, jumper or replace fuel relay |
| No pump even when jumped | ❌ Replace pump |
| RPM = 0 when cranking | 🔧 Replace CKP sensor (or re-plug if recently disconnected) |
| Cranks with clutch switch jumpered | 🔧 Replace clutch switch or install rally-style bypass |
| Fuel present, spark present, pump active | ✅ Check injector pulse / fuel pressure regulator |
🎯 Final Checklist (Top 5 Fixes)
- 🔌 Bypass clutch switch to verify starter circuit
- 🔄 Jumper fuel pump to verify power and operation
- 🧠 Scan/log RPM to confirm crank sensor function
- ⚙️ Check fuel pump relay/fuse and swap with known good
- 💡 Inspect ground straps + ECU grounds for corrosion or looseness
Would you like:
- 📄 A “Field Fix” guide for testing all these circuits roadside?
- 🧰 A wiring diagram showing clutch switch → relay → fuel pump → ECU logic?
- 🧠 A RomRaider logger profile prebuilt for this fuel-starvation scenario?
Let me know what you test or hear next — I’ll walk you through the next move.