[CumminsBoss5.9]

I've got an 03 that won't start below around 35f unless I have it plugged in for awhile. It doesn't smoke at all at start up. when I talked to my local diesel shop they didn't think that it was injectors. they figured grid heater most likely as there is power to the heater when it cycles. But it has about 9.5v at the heater. is that enough that it will work or is that too big of drop? when I had the intake horn off I would feel the heater and it would be warm but could put my had right by it so not very hot. So any info on what I need to be testing or looking for would be much appreciated. Been fiddling with this forever and am getting annoyed lol. Thanks for the help!

 

[N of 60]

Sounds like you do have issues with your grid heater but you also have others as your truck should start absolutely no problem at 35°f with out any help. My 97 or my 2011 are able to start at -15f without artificial help.

 

[rghavana]

How many miles?
Most common cause of your issue is worn injectors.
Can test injector return flow to rule them out.

 

[CumminsBoss5.9]

How many miles?
Most common cause of your issue is worn injectors.
Can test injector return flow to rule them out.

its got 228000. I was thinking injectors too after reading other guys talk about the problem but the guy I talked too at the diesel shop said he didn't figure injectors cause it doesn't smoke at all on cold start and never hazes or nothing. I just put a different grid heater on and the temp got up to 380f so obviously its working but is it supposed to be hotter?

 

[rghavana]

It wont smoke because the fuel injector(s) never fire fuel into cylinder, the ECM wont fire injector(s) because rail pressuree is to low, so fuel goes back into tank thru return plumbing.

 

[CumminsBoss5.9]

It wont smoke because the fuel injector(s) never fire fuel into cylinder, the ECM wont fire injector(s) because rail pressuree is to low, so fuel goes back into tank thru return plumbing.
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So if my rail pressure is normal that would rule out injectors? If it was returning a bunch of fuel to the tank seems I would be getting really good MPGs. On one trip I did last fall I calculated it to be 14mpg with highway driving. but maybe I miscalculated.

 

[rghavana]

Yes, if Rail pressure is above threshold of setpoint in ECM tuning, typically +1500 psi,
then solenoid on injector should activate releasing fuel to rest of the injector.
Since it is a common rail, any injector that has an issue effects the overall rail pressure.
With good compression, typical engine should ignite properly sprayed fuel at +/- 4000 psi.

IMO, best fuel mileage has really nothing to do with amount of return fuel, best fuel mileage occurs with the perfect atomization of fuel into cylinder with the perfect amount of air at the perfect time.
CP3 will draw fuel by vacuum but Lift pump really should always supply more fuel then needed for combustion as fuel system uses some fuel to cool/lube.
At idle should see 9+psi from lift pump above 0 psi at WOT.

 

[d.marcott243]

its got 228000. I was thinking injectors too after reading other guys talk about the problem but the guy I talked too at the diesel shop said he didn't figure injectors cause it doesn't smoke at all on cold start and never hazes or nothing. I just put a different grid heater on and the temp got up to 380f so obviously its working but is it supposed to be hotter?

Change your relays also. 380 is to hot. The grid heater should cycle off and on. I just did this to my 03 out of necessity replace bot grid heater relays and the grid heater. They are next to your second battery on the passenger side of the truck. The back one closest to the firewall is the one for the grid heater. Here is what you need to do that. Get them on Amazon for about $25.
Dorman 904-356 Intake Heater Relay Compatible with Select Dodge Models

 

[CumminsBoss5.9]

Change your relays also. 380 is to hot. The grid heater should cycle off and on. I just did this to my 03 out of necessity replace bot grid heater relays and the grid heater. They are next to your second battery on the passenger side of the truck. The back one closest to the firewall is the one for the grid heater. Here is what you need to do that. Get them on Amazon for about $25.
Dorman 904-356 Intake Heater Relay Compatible with Select Dodge Models

You say 380 is too hot? The heater cycles and got good power at the heater so can't imagine the solenoids being bad. I tried to start it when it was about 15f after I put the different heater in and still didn't start. I guess I should test my fuel pressure and my injectors and go from there.