I have new batteries in my 01 and here lately(colder weather) when I go out to start it at the end of the work day I turn the key and the battery meter is down around 8. Once I start it , it seems to bounce back and forth btw 8 and 14. The motor rpms change also. Is there some sorta charging relay that switches to each battery? Or any ideas what this could be? thanks

 

When the weather gets colder, your grid heaters will run when you turn the key to the on position. They draw a lot of current so your battery voltage will drop a lot. Once you have start your truck, they will continue to cycle on and off for up to a certain time period(approx 2 minutes, I can't remember the actual value) or a certain speed. Even though the truck is running and the alternator is charging, they draw enough current to drop the voltage way down. If the voltage keeps fluctuating after a few minutes, then you have a problem, otherwise you are just observing the grid heaters cycling.

 

Grid heater recycling.

 

I have the same symptom and it is the grid heaters cycling. Didn't have the problem until I replaced the relays which were both not working.

So when I start in cold weather the voltage is low (about 10 volts), check engine light is on for up to 30 seconds until the voltage starts to rise and the fuel pressure light is also on (I assume because the electric lift pump doesn't get enough juice).

I have new batteries from last year.

Do I need:
a) alternator rebuilt to get better charging at startup?
Or
b) A higher output alternator?
and/Or
c)new lift pump?


The low fuel pressure is scaring me but the light goes out when the voltage comes up.

Any suggestions appreciated.

 

Try plugging in the Block Heater on a timer for ~ 3 hrs before starting.

 

The block heater makes for easy starting but the intake heaters still cycle. Same symptoms.

 

Did you use the stock size replacement batteries?
My volt meter shows a low charge on cold morrnings too.
Sometimes I even get a check gauges light until the volt meter comes up.
I just add light throttle pressue to get the RPM up until the alternator catches up with the load, then let it warm up for a minute before heading to work..My batteries are 5 years old.

 

Yes, stock size replacement batteries.

Based on other posts in this and other forums, perhaps this is normal for the alternator not to be able to keep up, although my Check Gages light comes on whenever I start and the intake heaters come on.

My worry is that it impacts my fuel pressure. I think I'll replace my lift pump and see if it helps.

This is a stock truck which tows but is not asked to work too hard so I am going with a stock replacement pump - not from Dodge because they want to convert to an in tank pump.

Thanks

 

Its not really that the alternator cant keep up - its the fact that the grid heaters are drawing 100+ amps...what kind of voltage are you seeing at the batteries when you first start the truck? Should be 14.4 or so...

Dont waste your money on a new lift pump yet - add a FP guage. Im in Alberta and my pressure always reads lower in the winter.

 

Of course they will - the grid heaters heat the incoming air before it enters the combustion chamber - how is a block heater going to do that?

 

That is the cycle after the initial cycle

 

I have installed a fuel pressure light and that's what's making me paranoid.

It is indicating low pressure for about 5-10 seconds longer than the 'Check Gages' light is on which occurs because the voltage is low (looks like the threshold is about 10 volts).

Once the voltage starts to rise, the Check Gages light turns off and soon after the low fuel pressure light comes on.

After a couple of minutes warm up, the heaters continue to cycle, the voltage fluctuates from 11 to 14 volts. If I accelerate much before a couple of miles the fuel pressure light will come on.

I had a bit of this last year but now it happens every time I start.

Low was -24C in Winnipeg last night!

 

Whew! That is COOOOOLLLD! My lift pump pressure will drop from 15 to 14 when the grid heater kicks on, but it comes right back up. What is that low pressure light set to come on at?

 

The drop in Fuel Pressure from a stock LP would be caused from the large draw of the Grid heaters would it not? Being as they are affecting load on other electronics, would the Fuel Pressure being lower when the grid heaters are on is because there isn't as much electrical current going to the LP, causing it to not pump as fast/hard?

 

Yeah, I think you guys are right...fuel pressure generally comes up after the truck is warmed up some. The grids are drawing 100 amps or more and this is likely causing the light to flicker.

This is why you need a gauge in the cab thedblc. It doesnt have to be abything fancy - it doesnt even have to be lighted - it just has to be a guage.

Do you know what pressure the switch operates at?