Glow Plug Replacement
How are glow plug issues diagnosed?
Diagnosing a glow plug is most easily done with a computer scanning tool. The OBD code set for the glow plugs indicates that at least one glow plug was not in specified range. The technician will use that information, and use the scan tool to cycle the glow plugs on, then off. Reading circuit voltage for all of the glow plugs will show which one is faulty.
How is a glow plug replaced?
Locations for glow plugs are mostly simple to access, and replacement requires that the battery is disconnected, the glow plug is disconnected from an electrical connection, and unscrewed like a spark plug. The threads in the cylinder head are inspected, cleaned, and, if specified, coated with an anti-seize compound. The old glow plug will be inspected for signs of the engine running poorly. The new glow plug is screwed in, then its connector is plugged in. After the battery is reconnected, the glow plugs should be tested on a cold start, preferably after several hours of sitting.
RepairPal Recommendations for glow plug issues
We advise testing components before changing them, unless that component is being replaced in accordance with the factory scheduled maintenance interval. Failing to test parts very often causes good components to be thrown out, along with the money spent on replacement.
What to look out for when dealing with glow plug issues
Glow plugs are the equivalent to spark plugs in a gasoline engine. They are not interchangeable, and powering a glow plug when not installed can lead to severe burns, fires, damage, or other injury to self and others. Lastly, on-board diagnostic (OBD) scanners may function in most vehicles, but not in select American trucks. The scanner should be universal, but some vehicles simply alert that there is no connection. For these situations, there may be an issue with the OBDII port or the scanner, or there may be a compatibility issue between the two.
Can I replace the glow plug myself?
Glow plugs can be changed by most people, and the job can even be a fun project for a weekend. Things can get tricky when trying to access the glow plugs, but generally, diesel engines are less cluttered than gasoline engines, and accessing hard to reach components is a little less of a chore. This will not be true for many diesel powered sedans, as the need for additional regulated components since the late 1990's has turned the already-too-small engine compartments into cramped spaces. For vehicles with access issues that are too difficult overcome, or if glow plug testing is needed, consult a certified technician to help you with this repair.