Engine/Transmission (1998.5 - 2002) Sudden drop in MPGs

[Hobart]

My mpgs dropped by at least 1 1/2 miles per gal. around the first of October. Wonder if thats because of winter fuel here in Colorado or if my Van Aaken is giving up the ghost? Air filter looks dirty but the guage says its alright.

 

[MTreff]

The place you fuel at most likely changed from LSD (500ppm sulfur) to ULSD (15ppm sulfur). I operate a truck stop and have received many complaints of decreased mpg after we went to ULSD.

 

[24V-DSL]

Dirty or out of spec IAT sensor?

 

[Crazy Horse]

Winter Fuel Sucks. When I lived in Anchorage during the winter months the 02 went from 14-15 mpg city driving to 10-11. You could tell as soon as you started burning the 1st tank of the stuff the 1st part of October, no power either. Seemed to have the consistancy of water. That has to be hard on the motors.

 

[barbwire]

mpg drop

I have been having a mpg drop with my 04, since about 3 weeks ago. Although it has been more like 3 mpg, than 1. 5. Changed fuel filter, air filter, and have made sure that I have put nothing in but #2 fuel. Something is amiss, but, maybe mine is a mechanical failure. Another story maybe.

 

[Mr. C]

Welcome to winter

 

[LBello]

i have a 99 with 300hp inj plus the tst comp on 2. Don't really know how much power that is but i put in 23 gallons and i had 400 plus on the trip meter. I figured it out to 18. 3 mpg. I just put some stage 4 and will see where i'm at by this weekend. i wonder if additive would help any with this new crappy fuel

 

[dpuckett]

The ULSD is SUPPOSED to have better lubricity than the LSD (I read that here somewhere when doing research recently), but that is coming from the oil companies, not an independent lab. I'd use a lubricity additive along with some kind of antigel if that is a factor in your climate.



I noticed a ~2mpg drop recently, also. Thought it may be the engine or fuel pump, but might just be the ULSD.



Daniel

 

[mhenon]

ULSD doesn't have more lubricity than LSD but they do add a lubricant to try and bring it up. I'm adding extra lubricant too as I don't want the minimum required by law... I want more than enough to keep the IP happy.

As to mileage it looks like ULSD has less energy than LSD so you might see the mileage go down somewhat. The difference might be like going from summer to winter fuel.

Mike

 

[MTreff]

ULSD (15ppm) has alot less lubricity than LSD(500ppm). As I stated above many of my customers have noticed a . 3~. 7 mpg loss but that is is in a tractor trailer. I knew when we swiched to ULSD and saw my mpg drop about 1mpg after the switch. ULSD is shipped up the pipeline without lubricity additive and at a recent ULSD conference I attended they claimed ULSD has 6x less lubricity than regular unleaded when it is in the pipeline. At the rack lubricity additive is added so it really does depned on where you get your fuel as to the lubricity of it. I switched our truck stop to B5 Biodiesel to combat the lubricity issues and now my customers are claiming increased fuel mpg of about . 7~. 9mpg. Biodiesel has 300x the lubricity of ULSD and in just a B2 blend it increases the lubricity of ULSD 6x.



Only 20% of total US production is allowed to be LSD (500ppm) fuel and the availability will be very hard to find so look at your dispensers when you fuel. If it states it's not legal for 2007 engines it is 500ppm LSD. Keep your eye on that decal though because many of the stations are switching to ULSD after they know their tanks have been turned and they are certain they are at 15ppm fuel at the nozzel. If your not it's a $32,000 fine so the changing of the decals has been slow.



Mike

 

[Bob Wagner]

check it out

Intake Air Temperature Sensor Problem:



I thought I would share with everyone my findings about the low mileage problem, several people have complained about. Seems that no one has ever found a solution for it.

Maybe I have!



During our development I've become aware of the fact that the Cummins ECM calculates the fuel the injection pump has to inject, based on the signal of two main inputs.





Pressure in the manifold AND the Intake Air Temperature.



Obviously the most important input is the pressure measured by the MAP (Manifold Absolute Pressure) sensor. To make it simple, the higher the pressure, then more fuel will be injected. This does not mean that the Intake Air Temperature sensor is less important!

To make it simple again, the higher the air temperature in the intake, the less fuel will be injected.





Hot air is less dense than cold air, thus less fuel has to be injected as the temperature rises.



What happens if the IAT sensor gives a wrong reading of the temperature?



In my case, the IAT sensor wasn't able to read very cold temperatures, but also didn't read high temps. It was like it's temperature range was much shorter than it should have been. When I compared my original sensor to a new one, I also noticed that it's reaction time was way to slow!



Before I proceed, I would like to point out that NO code has ever been set in the ECM/PCM!





The ECM can only detect a completely dead sensor. ( Voltage too high/low )



After finding out that my stock sensor was off of it's values, I proceeded to install the new one.





Installation is very simple. All you need is a 22mm socket and the ability to climb onto the engine since the IAT sensor is located in a very uncomfortable position. It's at the end of the cylinder head towards the firewall, on the driverside.





Here's a link to see where it is located:

http://dodgeram.org/tech/dsl/mt_2_feb98/fuel_sys_comp.htm





Once the new sensor was in, I noticed immediately that the EGT's at idle were about 75°F lower!!! Cruising at 85 the EGT's dropped about 100-120 degrees!!!





Great, and the mileage? Driving like I normally do, MPG is better by 1. 9 miles per gallon!





Yes, that's the number!



Sure, I can't claim that everyone with the "low mileage" has a bad IAT sensor, but I think it's worth it to give it a try. Obviously, I don't know how your mileage will increase, but from what I've seen through the WWW, several people seem to have the same problem like I did!



In my case, since the IAT sensor never gave an high enough reading of the temperature, the ECM was fooled into thinking that the air was cooler than it was in reality. Thus it added more

fuel than could be burned. This little more fuel added wasn't enough to increase performance, but was enough to KILL mileage.



Hope this helps.

Marco.

 

[SnoKing]

ULSD (15ppm) has alot less lubricity than LSD(500ppm). As I stated above many of my customers have noticed a . 3~. 7 mpg loss but that is is in a tractor trailer. I knew when we swiched to ULSD and saw my mpg drop about 1mpg after the switch. ULSD is shipped up the pipeline without lubricity additive and at a recent ULSD conference I attended they claimed ULSD has 6x less lubricity than regular unleaded when it is in the pipeline. At the rack lubricity additive is added so it really does depned on where you get your fuel as to the lubricity of it. I switched our truck stop to B5 Biodiesel to combat the lubricity issues and now my customers are claiming increased fuel mpg of about . 7~. 9mpg. Biodiesel has 300x the lubricity of ULSD and in just a B2 blend it increases the lubricity of ULSD 6x.



Only 20% of total US production is allowed to be LSD (500ppm) fuel and the availability will be very hard to find so look at your dispensers when you fuel. If it states it's not legal for 2007 engines it is 500ppm LSD. Keep your eye on that decal though because many of the stations are switching to ULSD after they know their tanks have been turned and they are certain they are at 15ppm fuel at the nozzel. If your not it's a $32,000 fine so the changing of the decals has been slow.



Mike

From the clean diesel . org site:



Q. Will I need to put an additive in my fuel tank to replace the lubricity that was provided by the higher sulfur content?



A. Like Low Sulfur Diesel fuel, ULSD fuel requires good lubricity and corrosion inhibitors to prevent unacceptable engine wear. As necessary, additives to increase lubricity and to inhibit corrosion will be added to ULSD fuel prior to its retail sale. With these additives, ULSD fuel is expected to perform as well as Low Sulfur Diesel fuel.





Chris

 

[MTreff]

From the clean diesel . org site:



Q. Will I need to put an additive in my fuel tank to replace the lubricity that was provided by the higher sulfur content?



A. Like Low Sulfur Diesel fuel, ULSD fuel requires good lubricity and corrosion inhibitors to prevent unacceptable engine wear. As necessary, additives to increase lubricity and to inhibit corrosion will be added to ULSD fuel prior to its retail sale. With these additives, ULSD fuel is expected to perform as well as Low Sulfur Diesel fuel.





Chris

"ULSD fuel is expected to perform as well as LSD"



It was expected but in many areas as I stated acording to the many trucking companies I am in contact with and who check mpg as a ritual, since ULSD it has been proven that many engines have noticed a decrease in mpg using ULSD. This is information I'm passing along of which I had relayed to me. The information you received is biased and the long term effects of ULSD is still not known. The cold flow properties of ULSD are different from LSD and the cold filter plug point with ULSD has been found in some initial testing to be much higher than that of LSD. ULSD in the stream has also been coming in at around 6~10ppm in an effort for suppliers to meet the 15ppm mandate by oct 15th. So again, the testing is still not with acual 15ppm ULSD. Time will tell... .

 

[Cummins724]

My mpgs dropped by at least 1 1/2 miles per gal. around the first of October. Wonder if thats because of winter fuel here in Colorado or if my Van Aaken is giving up the ghost? Air filter looks dirty but the guage says its alright.

I had a sudden drop in mpg one time & thought it was gonna be a bad sensor etc. It turned out that I had a dirty air filter & low tire pressure. I noticed a little more smoke when it happened & decided to clean my filter & rotate the tires while I was at it. I always check pressure in tires when rotating & that was my problem... . not to say it is yours, but a suggestion. My friend had a similar problem & it turned out that he had a bad wheel hub bearing which was hanging up just enough to drop his mpg's. Just some suggestions.

 

[DSpencer]

For lubricity, I think what SNOKING posted is true. The additives put in the diesel locally should provide the lubricity equivalent to the LSD fuel. Where the difference is the energy that the ULSD provides. In Transport Topics mag I read where the ULSD is supposed to have 1 percent less energy than LSD. With the new regulations for the 2007 engines the industry is expecting a loss of 2-3 percent in their fuel efficiency with the new fuel.



That may or may not show or be discernable in our engines since we don't have to run all the traps and 1 percent less energy is hard to measure just by mpg readings.



I guess we will all know the truth about all this as we are all now the guinea pigs but for me I like the idea of cleaner burning diesel. I hope it doesn't make for a much higher cost to the transport industry as most of what we buy is influenced by it.

 

[DieselLady]

First of all, Hobart, if you are waiting for your filter minder to tell you when you need to change your filter you will be way past due for a long time. Those things usually don't show anything untill you are sucking a vacuum and that is a huge restriction.

Secondly, Bob Wagner, Thanks for the great information. I have been experiencing the same low milage and a lot more smoke. I have suspected my Map sensor as it has thrown a couple of low voltage codes but only when I turn up my comp and start messing around. It has been a lot colder now and I have noticed a lot more soot on the floor after starting up and backing out of the garage. I will be checking and replacing my IAT sensor first and possibly the map sensor too,(it is expensive). What you said makes great sense and I am sure that will be contributing to my mpg issues. Thanks for posting.

 

[barbwire]

Good info, but............

Intake Air Temperature Sensor Problem:



I thought I would share with everyone my findings about the low mileage problem, several people have complained about. Seems that no one has ever found a solution for it.

Maybe I have!



During our development I've become aware of the fact that the Cummins ECM calculates the fuel the injection pump has to inject, based on the signal of two main inputs.





Pressure in the manifold AND the Intake Air Temperature.



Obviously the most important input is the pressure measured by the MAP (Manifold Absolute Pressure) sensor. To make it simple, the higher the pressure, then more fuel will be injected. This does not mean that the Intake Air Temperature sensor is less important!

To make it simple again, the higher the air temperature in the intake, the less fuel will be injected.





Hot air is less dense than cold air, thus less fuel has to be injected as the temperature rises.



What happens if the IAT sensor gives a wrong reading of the temperature?



In my case, the IAT sensor wasn't able to read very cold temperatures, but also didn't read high temps. It was like it's temperature range was much shorter than it should have been. When I compared my original sensor to a new one, I also noticed that it's reaction time was way to slow!



Before I proceed, I would like to point out that NO code has ever been set in the ECM/PCM!





The ECM can only detect a completely dead sensor. ( Voltage too high/low )



After finding out that my stock sensor was off of it's values, I proceeded to install the new one.





Installation is very simple. All you need is a 22mm socket and the ability to climb onto the engine since the IAT sensor is located in a very uncomfortable position. It's at the end of the cylinder head towards the firewall, on the driverside.





Here's a link to see where it is located:

http://dodgeram.org/tech/dsl/mt_2_feb98/fuel_sys_comp.htm





Once the new sensor was in, I noticed immediately that the EGT's at idle were about 75°F lower!!! Cruising at 85 the EGT's dropped about 100-120 degrees!!!





Great, and the mileage? Driving like I normally do, MPG is better by 1. 9 miles per gallon!





Yes, that's the number!



Sure, I can't claim that everyone with the "low mileage" has a bad IAT sensor, but I think it's worth it to give it a try. Obviously, I don't know how your mileage will increase, but from what I've seen through the WWW, several people seem to have the same problem like I did!



In my case, since the IAT sensor never gave an high enough reading of the temperature, the ECM was fooled into thinking that the air was cooler than it was in reality. Thus it added more

fuel than could be burned. This little more fuel added wasn't enough to increase performance, but was enough to KILL mileage.



Hope this helps.

Marco.

Will this pertain to the 3rd gens as well? Thanks