I thought I'd just list the differences.
What Each Tool Does
PET‑4000
A basic spark-gap tester that checks whether a coil can produce a spark under realistic conditions (cranking or running).
Uses an adjustable gap (about 14–29 kV) to stress-test coil output.
Simple, quick “spark/no‑spark under load” tool — ideal for spotting weak or dead coils on small engines.
GTC505
A full ignition analyzer that measures spark voltage, burn time, dwell, RPM, and can show waveforms.
Diagnoses misfires, weak coils, or inconsistent ignition across cylinders.
Works with distributor, Distributorless Ignition System, and coil‑on‑plug systems — suited for professional diagnostics and tuning.
When to Use Each
Situation / Need Better Tool
Quick go/no‑go test on small engines PET‑4000
Suspected weak or intermittent spark GTC505
Multi‑cylinder or coil‑on‑plug systems GTC505
Simple “is there spark?” budget check PET‑4000
Detailed diagnostics or tuning GTC505
Key Trade‑offs
PET‑4000: Simple, cheap, but only shows “spark or not.” No data on spark quality or timing.
GTC505: Powerful and precise but more complex and expensive; may be overkill for basic engine checks.
Quick Summary
PET‑4000: Best for quick, stress‑under‑load spark checks on small engines.
GTC505: Best for in‑depth ignition analysis, especially on multi‑cylinder or electronic systems.
For ordinary lawn‑mower or generator diagnostics — use the PET‑4000.
For tricky misfires, tuning, or professional shop work — choose the GTC505.
Cheers
Max.
