Gauge readings

[bighorn35]

Guys; 2007 Duramax 2500 HD Classic

Couple of questions;

Is it normal for the ammeter to stay (at start up) around 12 volts for a minute before going to 14.3 Does the engine have to come to certain rpm(batteries @ 12.6 not running)

Also is 200kps (30lbs) @ idle to 400kps (60lbs) highway speed about normal readings.

Please reply; Thanks appreciate your expertise.

[dually2002]

If it's like the LB7 the glow plugs cycle for several seconds after start up. Oil pressure okay if taken at normal operating pressures.

[DickWells]

My LB7 (04) has always taken up to a half-minute before the volt meter jumps up to 14 +, so I'd say it's normal. And, mine has always run at between 20 lbs and 60 lbs under the same conditions.

[jbplock]

My 03 LB7 does the same .. I believe the voltage drop is due to the intake air heater which comes on for a period of time after a cold start. :)

[rapidoxidationman]

There's an intake air heater on the LB7??? Having completely disassembled, bolt by bolt, the top end of my engine and heads I can definitively say there's not an intake air heater on my LLY. Alldata shows the repair OEM part number to be "not listed" and the price to be "$0.00". Oddly, it rates the replacement of the intake air heater RELAY as a "B" level job that takes .4 hours, but again no part number is provided. YMMV.

I was under the impression that the glow plugs pull enough juice to drop the voltage down. After the afterglow cycle is complete, the glows go cold, amps drop considerably, and volts jumps up.

[DmaxMaverick]

Look at the intake pipe just above the plenum. There should be a bung in the pipe with what appears to be a large glow plug and a single (12ga) wire attached. This is for the LB7, 01-04. Or, it could be of only a year or two of fed smog trucks that deleted it, but the bung, blank or plugged, should still be there. There was a model year or two federal smog trucks that didn't have a heater (all CA/N.E. smog trucks have it), but the bung should still be there. My Alldata for the 2001 model also shows no parts data for the plug, but the location and description is there. The CA and fed controller and relay systems are different, but .4 hours repair time sounds about right for either.

The glow plug system operates for a few seconds during a start cycle, and may "after glow" after the engine is started, depending on temperatures. The intake heater can operate, constant or intermittent, for a minute, or several minutes, also depending on temperatures. The early truck charging system is somewhat "real time", with quick gage changes according to the load. Later truck voltage regulation is somewhat buffered, with more gradual changes during and after loads. 2001 and 2002 trucks have/had a headlamp "dip" that occurred when returning to idle. A calibration update helped the condition, but didn't correct it completely. My upgraded alternator along with the update eliminated it. The 2003 and later trucks shouldn't have the condition.

[bobt]

My 2009 has had this delay of 30 seconds or so before going to 14 volts since day 1. I've never had any problems with it. I think it is normal but I don't know what causes it.
Bob