Why Does My C10 LS Swap Crank but Not Start? (Top Fixes)
Most no-starts are simple — once you check the right things in the right order.
Short answer: most LS swap crank-no-start issues come down to VATS (anti-theft), fuel pressure, no injector pulse, missing crank/cam signal, or bad grounds. Don’t guess — check in a clean sequence.
“No-starts feel complicated because builders check random things. A sequence turns chaos into answers.”
Step 1: Confirm Fuel Pressure (Not Just “Fuel”)
Verify you have correct EFI pressure at the rail. A pump can run and still not produce stable pressure if wiring is weak, the filter is restrictive, or the regulator strategy is wrong.
Step 2: Check VATS (Anti-Theft)
If the engine cranks but won’t fire and your basics check out, VATS is one of the most common swap culprits. Many factory ECUs require VATS to be disabled for swap use.
Step 3: Confirm Spark + Injector Pulse
- Spark: verifies ignition and crank signal basics
- Injector pulse: verifies ECU is commanding fuel
Step 4: Grounds and Power Distribution
Poor grounds create “ghost problems.” Use clean metal contact, add redundant grounds, and avoid grounding to painted surfaces.
Shop: Electrical & Wiring | Fuel & Cooling
Make No-Starts Less Likely
Clean wiring, stable fuel pressure, and proper grounding prevent most crank-no-start headaches.
