This 2013 Ford F-150 with a 3.5L engine exhibited a symptom of “Crank/No-start.” The vehicle was driven flawlessly off-road and crossed a shallow creek before the engine stalled suddenly and wouldn’t restart.
Motor Age Technical Editor Brandon Steckler and technician Clay Cowell in Montana were faced with a challenge with this Ford F-150. They challenged you to help come up with the correct diagnosis.
What would you recommend doing next, given the data bullet points in last month’s challenge? Given this information, what would you do next?
- Replace the CKP sensor.
- Inspect CKPreluctor with borescope.
- Replace damaged crankshaft.
- Update PCM software.
For those of you who chose answer No. 2, congratulations! The 1 Hz-anomaly yielded conclusive evidence that the fault was related to the crankshaft. The CKP sensor was removed, and a borescope inserted in its place.
The crankshaft was rotated until damage was seen on a section of the reluctor teeth. A stone made its way into the bell housing of the transmission and caused the damage.
Answer No. 1 is incorrect. Since the anomaly in the CKP sensor waveform occurred once per crankshaft rotation, it eliminates the sensor as the fault.
Answer No. 3 is incorrect, although some crankshafts have the CKP reluctor teeth machined into the crankshaft itself, this configuration has a bolt-on reluctor that can be replaced. Replacing the crankshaft would not fix the issue.
Answer No. 4 is incorrect as well. Updating the PCM software can correct some issues that surface on vehicles. However, the fault present on this vehicle is an input issue and new or updated software will not allow the PCM to recognize the faulty input any better than the original software.
Be sure to read the next Motor Age issue for the answer to this month’s challenge and what was discovered!
