Hard, No Start, Excessive Smoke On Start Up (Replace Glow Plugs)

Customers may comment on a hard start cold (normally under 32°F or 0°C) with excessive white or gray smoke on vehicles that have had glow plug replacement after January, 1999. This bulletin does not apply to original equipment glow plugs installed in production vehicles, only service plugs.

Certain service 11G glow plugs (P/N 25168651 or equivalent) produce insufficient heat energy to the cylinder during cold starting pre-glow.

This table may be used to help identify glow plug type.

Perform normal diagnostics on the hard start, gray or white smoke condition. If normal diagnostics do not lead to resolution of the symptom, determine if the glow plugs have been replaced since January, 1999. If they have, it will be necessary to determine if the service glow plugs are low heat energy units. Remember, not all 11G glow plugs are low heat energy plugs even though they do have the same part number (P/N 25168651). It is important to properly identify the type of glow plug using visual characteristics and Julian date prior to initiating any repairs.

The low heat energy 11G glow plugs can be visually identified by performing an examination of the plug. There are three identifying characteristics of these glow plugs:

1. The low heat energy glow plugs have a gray colored insulator (figure 1, item 1).
2. The hex head of the plug has a stamped in Julian date (figure 1, item 2) of 3388 or higher. The Julian date is the day of the year (such as December 3 being 337, December 4 being 338, etc.), followed by the last digit of the year (1998 being 8, 1999 being 9, etc).
3. Model identification located below the threads (figure 1, item 3) is stamped "AC 11G////U.S.A.////" (note that the low energy plugs have the slashes //// between the letters).

In figure 2, this 11G style glow plug is not a low heat energy glow plug and should not be replaced unless standard glow plug diagnostics indicate. This glow plug can be identified by these three characteristics:

1. The insulator color is black (figure 2, item 1)
2. The hex head of the plug has a stamped in Julian date (figure 2, item 2) of 3378 or lower. The Julian date is the day of the year (such as December 3 being 337, December 4 being 338, etc.), followed by the last digit of the year (1998 being 8, 1999 being 9, etc).
3. Model identification located below the threads (figure 2, item 3) is stamped "AC 11G U.S.A." (note that this model glow plug does not have the slashes between the letters)

In figure 3, this is the new style BERU glow plug (P/N 12563554) used in current production vehicles. This is not a low heat energy glow plug and should not be replaced unless standard glow plug diagnostics indicate. This style glow plug can be identified by the following three characteristics:

1. The insulator color is black (figure 3, item 1).
2. The hex head of the plug does not have a stamped Julian date (figure 3, item 2).
3. Model identification located below the threads (figure 3, item 3) is not stamped. It does have an ink identifier of "AC DELCO" and some other ink text.

If new glow plugs are required, use BERU style, P/N 12563554 (figure 3), or acceptable 11G, P/N 25168651 (figure 2). It is ok to mix the BERU style plug and the acceptable 11G style plug for service installation.

Parts are currently available from GMSPO.

For vehicles repaired under warranty, use: