Unlike the Cummins, which uses an intake grid heater, the 6.7L Power Stroke relies on individual glow plugs to warm the combustion chambers for cold starting. A glow plug control module energizes the plugs before and, on cold days, briefly after startup. When plugs or the controller fail, cold starts get long, rough, and smoky, and you may see a wait-to-start indicator behave abnormally.
How the system works
- Each cylinder has its own glow plug that heats to aid ignition of the cold air-fuel charge
- A glow plug control module manages timing and duration based on temperature
- Afterglow keeps plugs energized briefly post-start to smooth cold running and cut white smoke
Symptoms of glow plug problems
- Hard, long cranking on cold mornings
- Rough idle and white smoke right after a cold start
- A glow plug or controller trouble code
- Misfire-like stumble that clears as the engine warms
- No noticeable cold-start trouble in mild weather, worsening as temperatures drop
Testing before replacing
Do not assume every rough cold start is a bad plug. Scan for glow plug circuit codes that often identify a specific cylinder. Individual plugs can be resistance-tested, and the control module and its power feed can be checked for proper operation. Wiring and connector corrosion cause faults that mimic bad plugs, so inspect the harness. Because access can be tight, confirm the fault before pulling parts.
Replacement tips
- Work on a cool engine and use care so a plug does not seize or break off in the head
- Replace with the correct plugs for your model year and torque them properly
- Address the control module only after confirming its circuit, not as a first guess
- Clear codes and verify a clean cold start after the repair
Frequently asked questions
Does the 6.7L Power Stroke use a grid heater like a Cummins?
No. It uses individual glow plugs and a glow plug control module, not an intake grid heater.
Can I drive with one bad glow plug?
In warm weather you may not notice, but cold starts will suffer and unburned fuel adds strain. Fix it before winter.
How long do glow plugs last?
They can last many years, but heat cycling wears them out over time. Age, climate, and cold-start frequency all affect their life.
Need parts or a second opinion? The team at Core Diesel Parts can match the correct component to your VIN and build year. Email sales@coredieselparts.com and we will point you to the right part the first time.
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