# A couple of diesel Q's



## boraz (Aug 29, 2013)

1. dunno


2. you mean like a choke?....the glow plugs aid in starting when needed, and the fuel injection pump will be advanced to aid starting


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## DJSW (Apr 8, 2014)

1. Do you mean the alt that shuts off when the battery is at full load and then starts back up when there is an increase in draw? Then yes it does. If you scroll through your gauge menu you can see voltage. Sometimes it is at 12V, others 14V+.

2. See above.


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## 1877 iris ave (Sep 23, 2011)

Ok the reason I asked Question #1 is that my voltage on the DIC seems to always read 15.3V. I just returned from a 200 mile drive and the voltage was consistently 15.3V. I even turned everything (radio, lights, heat) off for 50 miles. Still the V stayed at 15.3 but when I read the V with the key on but the engine off the V is 12.2. This to me indicates that there is something wrong. But it was 8 degrees out this morning and the engine started without trouble. I called my local dealer and asked. His answer was " as long as there is no check engine light the alternator is functioning normally" What do you all think?

And the reason I asked Question # 2 is that I was wondering if the computer causes the injectors to create a richer mixture when the engine is cold. Driving around a congested city for three days, a total of 50 miles, never more than 3 mile trips, average temp 20f, I averaged 19 mpg and I was driving conservatively. this is much worse than my 2012 eco m gets. i know i have only 1000 miles on the diesel but I'm surprised at such low mpg.


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## TDCruze (Sep 26, 2014)

I noticed that mine was reading 15.3V today while driving, I am sure this is normal. 

Yes, the engine will run more rich before reaching operating temperature. If you are doing mainly very short trips always from a cold start your engine will likely never reach full temp and you will definitely see much lower MPG than those that are hot. It would be no different with a gas engine that is cold.


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## MilTownSHO (Oct 9, 2013)

The voltage is normal, mine tends to read over 15 volts when it gets cold out. In the warmer months I have seen it go from 12-14 volts.

The diesel takes a long time to warm up and driving in the city are not a good combination for mileage.


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## Aussie (Sep 16, 2012)

The diesel engine operates differently to the petrol engine as there is no butterfly in the intake, rather the amount of fuel supplied to the engine regulates the pick up and cruising speeds. Also once running the engine uses almost no electricity to operate as no coils or spark plugs to run. Old diesel engines could only be switched off by cutting off the fuel or they would just keep running.


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## diesel (Jun 8, 2013)

1877 iris ave said:


> Ok the reason I asked Question #1 is that my voltage on the DIC seems to always read 15.3V. I just returned from a 200 mile drive and the voltage was consistently 15.3V. I even turned everything (radio, lights, heat) off for 50 miles. Still the V stayed at 15.3 but when I read the V with the key on but the engine off the V is 12.2. This to me indicates that there is something wrong. But it was 8 degrees out this morning and the engine started without trouble. I called my local dealer and asked. His answer was " as long as there is no check engine light the alternator is functioning normally" What do you all think?
> 
> And the reason I asked Question # 2 is that I was wondering if the computer causes the injectors to create a richer mixture when the engine is cold. Driving around a congested city for three days, a total of 50 miles, never more than 3 mile trips, average temp 20f, I averaged 19 mpg and I was driving conservatively. this is much worse than my 2012 eco m gets. i know i have only 1000 miles on the diesel but I'm surprised at such low mpg.


Welcome to the forum! Winter, short trip MPG is not so great, but summer MPG on the highway is awesome. I have about 41.7 MPG lifetime average over 87K miles. Below is my worst and best. (I actually may have been able to get it lower, i can't remember)

http://www.cruzetalk.com/forum/64-c...-jams-frigid-temps-snowstorms-record-low.html


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## revjpeterson (Oct 2, 2013)

1877 iris ave said:


> Ok the reason I asked Question #1 is that my voltage on the DIC seems to always read 15.3V. I just returned from a 200 mile drive and the voltage was consistently 15.3V. I even turned everything (radio, lights, heat) off for 50 miles. Still the V stayed at 15.3 but when I read the V with the key on but the engine off the V is 12.2. This to me indicates that there is something wrong. But it was 8 degrees out this morning and the engine started without trouble. I called my local dealer and asked. His answer was " as long as there is no check engine light the alternator is functioning normally" What do you all think?
> 
> And the reason I asked Question # 2 is that I was wondering if the computer causes the injectors to create a richer mixture when the engine is cold. Driving around a congested city for three days, a total of 50 miles, never more than 3 mile trips, average temp 20f, I averaged 19 mpg and I was driving conservatively. this is much worse than my 2012 eco m gets. i know i have only 1000 miles on the diesel but I'm surprised at such low mpg.


When the motor is running, it displays the amount of voltage being pushed to the battery by the alternator (to run DRLs, computers, instrument cluster, accessories, etc.). When they key is on, but the engine is not running, it will display the voltage of the battery itself. I see anything from 12.1 to 15.9 normally, and had the same on my Grand Prix with a variable alternator. On one extreme temperature occasion (-18F) I did see the alternator voltage push as high as 16.4. 

For the driving conditions you describe, 19mpg does not sound out of line. I can drive my 100 mile commute, get 50+mpg, then after just 5 miles of driving around town at 30mph with about 3 stoplights per mile, I'm already down to the high 30s. I've also noticed that engine starts play a big role in killing fuel economy on our Diesels. The history graph on the eco menu of the DIC shows the past 10 3-mile segments you have driven. If I drive a 3-mile segment around town, that bar will usually still be 1/3-1/2 of the maximum height. However, if I stop and restart the engine 2-3 times during that 3 miles, the bar goes down to nothing. Similarly if I am driving on the highway getting 50+mpg and pull into a rest area or convenience store, then restart the engine and get right back on the highway, it cuts that bar in half just from the one restart.


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## 1877 iris ave (Sep 23, 2011)

thanks gentleman, you input has helped me a lot

enjoy


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