2012 Chevrolet Express 4500 Crank No Start Issue at 320,000 Miles

Crank/no start on a 2012 Express 4500 with 320k miles — most likely, you're looking at a fuel delivery issue or a crankshaft position sensor failure. High mileage makes fuel pump failure a top suspect, but sensor failures are common too. If you get no RPM signal on the scanner during crank, lean toward the sensor. If you have RPM but no fuel pressure, it's the pump.

Most likely culprits

• Fuel pump module — High mileage, common failure, especially if you don't hear it prime or have zero fuel pressure.
• Crankshaft position sensor — If you get no RPM signal during crank or a P0335 code, this is your guy.
• Ignition/fuel relay or fuse — Quick check, but less common unless you had electrical issues recently.

How to narrow it down

1. Scan for codes — Even if the check engine light isn't on, look for pending/history codes (especially P0335, P0340, P0230, P0689).
2. Check RPM signal during crank — If scanner shows zero RPM, suspect crank sensor or wiring.
3. Listen for fuel pump prime — Turn key to ON, listen for pump hum from rear. No sound = pump or relay/fuse.
4. Check fuel pressure at rail — Use a gauge. Should see 55-62 psi during crank. Zero = pump, relay, fuse, or wiring.
5. Check spark — Pull a coil or plug, check for spark during crank. No spark = sensor, ignition module, or PCM.
6. Check relays/fuses — Quick visual and swap test for fuel pump and ignition relays/fuses.

Possible parts (if needed)

• Fuel pump module
• Crankshaft position sensor

A few questions

• Do you hear the fuel pump prime when you turn the key to ON?
• Is there any RPM signal showing on a scan tool during crank?
• Any recent electrical work, battery swaps, or blown fuses before this started?

Let me know what you find on those quick checks — that'll pin it down fast.