Why does it take so long to get up?

[Luis]

Why does it take so long to get the volt meter up? Lately it seems to take the volt meter much longer to get up to 14v range after a cold start. It's always taken a few seconds but lately it takes between 10-16 seconds. Occasionally (while driving) the meter will drop when I take my foot off the accelerator and all lights, fans etc. dim for a few seconds and then returns to the 14v range. Could the alternator be the cause? The batteries are 5 months old and have less than 6k behind them.

01 DA w/139k
Thanks!

[DmaxMaverick]

Sounds like you need a later PCM calibration. Under warranty, they are free. You'll have to pay about 1/2 hour shop labor at the dealer. If you haven't done it, have the TCM updated, as well. There were a lot of refinements along the way, and the latest calibration is a significant improvement over the original 2001.

The calibration will refine the voltage regulation (controlled by the PCM--no "voltage regulator", like older models), and help minimize the voltage drops when you get off the pedal (this was an early 2001 complaint, and resolved with the calibration before the end of the model year production), and increases the overall line voltage at other times. Also, with the colder temps, the cold starts will cause more voltage delay with the intake heater and glow plugs operating longer. Mine always takes 10-20 seconds on a cold morning before the gage "jumps" back up to normal.

Alternators fail, but it doesn't sound like yours is. A poor connection somewhere (good luck!), perhaps.

[Marc Miller]

I have the same problem with mine... seems like the colder it is, the longer the voltage stays around 9 vdc. Bad intake heater? I have already replaced one alternator... (they ain't cheap)

[More Power]

The "Wait to Start" lamp on the dash will illuminate when the glow plugs are energized. After that, the delay in the voltage gauge from reading above 14v is due to the intake heater. It's all temperature related. Colder=longer. Sounds like yours is working OK...

It's usually heat and electrical load over a longer period of time that kills alternators (like towing with lots of lights on during a hot summer night).

Jim

[THEFERMANATOR]

The ECM energizes the alternator circuit and has some control over it, but not full control as the alternator still has it's own voltage regulator in it. ALL of the LB7 ECM's have afterglow in them of up to 30 seconds depending upon the engine temp. I know I turned my afterglow down quite a bit on mine via EFILIVE as I see no reason for so much glow plug time after it's running. Also when the glow plug/wait to start light goes off, the glow plugs will stay on for a predetermined amount of time. And yes the intake heater will also come on and draw it's 35+ amps if the outside air temps are below about 60 degrees, and below 20 it can run for 3 minutes after a cold start. From looking at all of the generations of LB7 tunes with EFILIVE, I can tell you that the 04 has the longest glow plug times of all of them.

[THEFERMANATOR]

These pics may help to understand the glow plug times and intake heater times. These are from a bone stock 03 federal emissions operating system. The first one is how long the glow plugs can stay on before the engine starts(your glow plug will go out long before these times). The second one is how long they will stay on after you start it. The third one is for the intake heater after it's running. And the 4th one is how long the intake heater will stay on without the engine being started.

[Luis]

Thanks everyone!...great information. So it sounds like I need to update the ECM & TCM to solve the issue...Anything else I may have missed in the responses?

[THEFERMANATOR]

Thanks everyone!...great information. So it sounds like I need to update the ECM & TCM to solve the issue...Anything else I may have missed in the responses?

Updating the ECM won't change how long it takes for the voltage to come back up. Newer operating systems actually have LONGER glow times than the early ones.

[DmaxMaverick]

Updating the ECM won't change how long it takes for the voltage to come back up. Newer operating systems actually have LONGER glow times than the early ones.

Actually, it does to some degree (not scientific, just real world observation of several vehicles). How much depends on climate, overall system health, among any other variables. The line voltage was increased by about .75~1.5V. The actual gage indication should be in the 14.5~15V range after the update (13~14V before). What I've seen is not so much a sudden recovery to "normal", but a quicker creep up to the normal range during, rather than a gradual recovery after the cold start system stops.

That said, the gage indication is not a direct reflection on the actual line voltage. The immediate draw of current superficially pulls the voltage down, but the actual battery voltage varies little. The voltage sampling is in the path of the current draw, rather than the source or termination.

[Luis]

You guys are great...Now were getting some where...My gauge indication is in the 14.5~15V range. I have noticed this year the gauge is higher than it was in previous years (13-14v)(I thought it was just me) I had the injectors replaced and other work last year which included a PCM flash....Makes sense now....THANKS!