Low voltage when first starting up

[AHarris]

I just noticed a new thing the truck is doing, and it only does it for the first couple minutes after it's started up after sitting more than 12 hours. The headlights will dim when I give it some gas and the voltmeter will drop to about 10 or so volts for just a second until the engine returns to idle. This only happens when the engine is dead cold and I didn't give it a minute or two to warm up. After the truck has been running for about 3 minutes the problem goes away. Never happens with a warm engine that's been sitting for a couple hours... just dead cold.

Is this the grid heater warming the intake air on a dead cold engine? Should I let the truck run for a minute before driving? Just first time diesel owner operator error... or an indication that this could be an electrical problem and requiring a trip to the dealer?

No CELs or anything else out of the ordinary...

 

[sag2]

Grid heaters cycling, perfectly normal.

 

[AHarris]

Ok, do you guys normally let your truck run for a minute or two before taking off? Is that advisable?

 

[DBoggs]

I let mine run long enough to get oil pressure and to make certain it has got to the bearings and turbo. Then I just drive easy until I see the temp gauge move.



When I lived in NE Utah sometimes the grid heater would cycle for several minutes during the winter even after I was driving. The colder the air temp the longer they will cycle.



Duane

 

[MHammond]

I usually let it run thru the grid cycles a couple of times then on with eb, up idle and let cycles finish before moving then light throttle until warmed up.

 

[JimB1]

If your new rig is long term keeper... ,



For cold starts.



Don't touch throttle. Turn key on, wait for heater icon to cycle OFF, crank to start, don't touch throttle.



Closely listen 4-5 seconds (maybe keep door open) engine sound dramatically changes as oil galleries pressurise.



Increase idle to about 1200 rpm and watch ammeter for two grid heater cycles and/or 1 minute.



48re, select manual 1st, roll away goal is stay near 1600-1800 rpm for a bit.



Stay in manual 1st for 2-3 blocks, then manual 2nd for couple more blocks which will give TC lock-up about 26 mph, staying with manual 2nd up to 35 mph and about 2000 rpm.



If continuing with urban driving 35-45 mph, select D and OD OFF, gives 3rd gear direct then TC lock-up at about 36 mph and keeps rpm near 2000 until engine water temp raises to normal operation point.



If truck has sat several weeks, then allowing oil gallery pressurization becomes even more signifigant to re-supply drained turbo bearing assy before touching throttle, maybe 2-3 seconds longer.



Engine sound, 4-8 seconds after start will always reveal just when oil gallery pressurizes, regardless of how long it's been since last started.



Oil change tip: pre-fill new oil filter before installing makes for faster oil gallery pressurization with first start after oil change.



If rig has sat long enough for TC oil drain-back, which is really hard to know, place gear selector in neutral and high idle for 2-3 minutes is pretty safe bet based on transmission oil pump delivery rates at about 1200 rpm.





These are long term preventive maint. procedures and easily argueable, re effectiveness of wear & tear, by individuals from various levels of experience and knowledge working with mechanical systems.





YMMV.

 

[AHarris]

If it wasn't for this board, I'd be a diesel newbie making an unnecessary trip to the dealer and losing sleep over nothing. This is why I like the TDR so much! Thanks!

 

[sag2]

If your new rig is long term keeper... ,



For cold starts.



Don't touch throttle. Turn key on, wait for heater icon to cycle OFF, crank to start, don't touch throttle.



Closely listen 4-5 seconds (maybe keep door open) engine sound dramatically changes as oil galleries pressurise.



Increase idle to about 1200 rpm and watch ammeter for two grid heater cycles and/or 1 minute.



48re, select manual 1st, roll away goal is stay near 1600-1800 rpm for a bit.



Stay in manual 1st for 2-3 blocks, then manual 2nd for couple more blocks which will give TC lock-up about 26 mph, staying with manual 2nd up to 35 mph and about 2000 rpm.



If continuing with urban driving 35-45 mph, select D and OD OFF, gives 3rd gear direct then TC lock-up at about 36 mph and keeps rpm near 2000 until engine water temp raises to normal operation point.



If truck has sat several weeks, then allowing oil gallery pressurization becomes even more signifigant to re-supply drained turbo bearing assy before touching throttle, maybe 2-3 seconds longer.



Engine sound, 4-8 seconds after start will always reveal just when oil gallery pressurizes, regardless of how long it's been since last started.



Oil change tip: pre-fill new oil filter before installing makes for faster oil gallery pressurization with first start after oil change.



If rig has sat long enough for TC oil drain-back, which is really hard to know, place gear selector in neutral and high idle for 2-3 minutes is pretty safe bet based on transmission oil pump delivery rates at about 1200 rpm.





These are long term preventive maint. procedures and easily argueable, re effectiveness of wear & tear, by individuals from various levels of experience and knowledge working with mechanical systems.





YMMV.

Wow, I just start it, let it idle for about 10 seconds and drive it!

 

[JimB1]

Back in the day... , when I wasn't paying for my high performance military ride or twisting wrenches on it, I'd kick-the-tire, light-the-fire, and launch without returning 'til I was low on fuel or out of rockets & bullets... , or hitch-hiking back.



After a civilian career of precision mechanics and wanting current rigs to be last iron I buy, hopefully 25-30 more years, I'm doing what should get me there.



There-in is where the variations of arguement lie.

 

[upsyes]

I would like to refer back to the original posters question because mine is identical. In the 97 I USED to own the grid heaters cycled and the volt meter would drop and then come back up as they cycled off (repeat untill driven at 18mph or so). NOW I have a 2001 and the grids do the same thing as they should do, BUT! as was stated in the first post (and maybe overlooked?) when I LIGHTLY or BARELY press the accelerator pedal IN PARK the headlights dim SIGNIFICANTLY and when I release the pedal back to idle they go back to being bright. This is regardless of the grid heaters operation at the time. I don't see a volt drop at the meter when this happens. It doesn't make sense that the lights dim WITH any acceleration does it???? More rpms should drive the lights to a brighter state rather than a dim state I would think.



Also, at night, I feel like my headlights are just too dim or useless untill I hit the brights or hold the lever so ALL lights are lit and boy do I love that!



I appreciate your input in advance!



Eric

 

[DBoggs]

I would like to refer back to the original posters question because mine is identical. In the 97 I USED to own the grid heaters cycled and the volt meter would drop and then come back up as they cycled off (repeat untill driven at 18mph or so). NOW I have a 2001 and the grids do the same thing as they should do, BUT! as was stated in the first post (and maybe overlooked?) when I LIGHTLY or BARELY press the accelerator pedal IN PARK the headlights dim SIGNIFICANTLY and when I release the pedal back to idle they go back to being bright. This is regardless of the grid heaters operation at the time. I don't see a volt drop at the meter when this happens. It doesn't make sense that the lights dim WITH any acceleration does it???? More rpms should drive the lights to a brighter state rather than a dim state I would think.



Also, at night, I feel like my headlights are just too dim or useless untill I hit the brights or hold the lever so ALL lights are lit and boy do I love that!



I appreciate your input in advance!



Eric

When the grid heaters are operating, the faster the engine turns the more cold air is pulled across them. Thats why your lights are dimming. The grid heaters take everything the alternator can produce and that is why the lights stay dim. My 01, 05, 06 and now my 09 have all done this exact thing. I have seen mine cycle and the voltmeter won't pull down very much, I just attribute that to the meter being an approximation of the actual voltage. In other words it isn't much better than an idiot light.



As far as your lights being dim after the truck warms up, that I don't know about. Perhaps on your truck the plastic lenses on the headlights are cloudy from age? Maybe the bulbs are just old and need to be replaced. I suppose they could also just be out of adjustment. I know on my 05 they were adjusted too high from the factory and I couldn't see the road until I figured that out and adjusted them down. I guess it's also possible you might have a bad ground in the headlight circuit.



Duane

 

[upsyes]

Thanks for your input Duane.



What I think is weird is that all I have to do is just "touch" the pedal and the lights seriously dim and the second you "un-touch the accel pedal they go back to being seriously bright. Maybe the ECM just sees any accelleration at all and, based on ambient cold temps being within a certain range, further draws more amps through the heater grids. Obviously the dash lights get dim too, though I failed to mention that little tidbit earlier.



I will definitelly check all my grounds and replace what are probably original headlamps. It seems that grounds are a common problem.



The dim headlights seems to be a common thread on the TDR web sight and I will do a search to hopefully improve my lighting without having to replace my headlamp assemblies like most do. Also, you're right about possibly needing to adjust my headlamps.



Thanks again! Eric

 

[SteeleM]

Have a 2002 5. 9 and when I start the engine the volt gauge will show a discharge and the in less then a minute the volt gauge shows that it's charging. Check the batteries and there good,could it be the voltage regulater in the alternator that going bad? This happens everytime I start the engine,even when it's all warmed up it shows discharge and the in less than a minute it's charging. Do I need to replace the Alternator?

Thanks for your advice,

Mike

 

[upsyes]

Voltage is regulated via the PCM/ECM. There is no voltage regulator in the alternator. If your alternator is going bad then check witha mirror on the alt body and see if it is a Denso or Bosch and order a rebuild kit for it from Geno's garage. They are $35. You can bypass the Volt reg in the ECM by putting an external one mtd on the alternator. I have seen and read the thread before, just do a search and you will find it.



Eric

 

[grasmo]

Man there are some very smart people on here!If you guys ever need to know secrets of sharpening a lawn mower blade... ...

 

[upsyes]

Yes, as a matter of fact. Is it faster to sharpen the blade with the engine running or ???.....

 

[grasmo]

If the engine is running let your helper sharpen it. I honestly use a plasma cutter to sharpen mine, 10 seconds per blade. I cut a lot of grass hence the name Grasmo.

 

[MN Cummins Lvr]

If it wasn't for this board, I'd be a diesel newbie making an unnecessary trip to the dealer and losing sleep over nothing. This is why I like the TDR so much! Thanks!

Just mail a check to all TDR members for consulting fees so you don't lose sleep :-laf:-laf:-laf



Enjoy your new ride!



Paul