Fuel Mileage

[hoogkar]

#@$%!

Is there any chance that changing a rocker box gasket could do something that would severely effect fuel mileage?



I have been going back and forth with the dealer that something has happened that cut my fuel mileage by about 7 mpg running unloaded. My truck has run consistently about 19. 5 - 20. 5 for last 3 years - now last 2000 miles running about 12. 5 empty.

they replaced pusher pump into tank, found bad differential bearings in front axel and done several tests -they told me the cumputer read that over the last 13,000 miles I have averaged about 17 mpg.



This makes sence but that is because 11000 milles was at about 20mpg and the last 2000 was at about 12. 5 mpg.



I just realized that the drop in mileage occured aabout same time as relacement of rocker box gasket - any thoughts?????



I have read all the posts and did clean IAT - no change.



could this be an injector problem? - I have checked and do not think there is a sign of fuel in the oil.



PLEASE HELP! - New to this, not sharp on diesels

 

[jnelson]

When I first bought my 2001 auto it was a dog. Im talkin dog. Would not even pull a half loaded g/n in overdrive. I was very very disapponted. I eventually took it to a deisel shop where they did a valvebody upgrade and aput a VanAken chip in it. When I got it back I was elated!!

Come to find out months later it had a TSB for a misprogrammed computer. the chip took care of the problem. It took the factory setting a bumped it up.

Your problem might not be a computer based problem, but it worked for me. Get you and Edge EZ, something easy to take in and out. You might just like it and it might give you some extra mpg's.

 

[hoogkar]

I have a friend that let me use his to test and the power was much better but it did not fix the poor mileage.

 

[DerekW]

do you have any aftermarket egt or boost guages??? seeing in your signature that you have a jake brake. might it be starting to stick closed somewhat? use ur egt and boost gauges to diag lack of exhuast flow or lack of air for the fuel being sprayed. I know that in total all of my exhuast work has increased my mileage close to 3. 5 mpg but that may be compounded with the other mods that needed the flow. so there has to be severe negative effects on the engines efficiency when the jake brake is stickin. come to think of it thats what they were designed for to severely choke the efficiencies of our diesel air pumps. also to check injectors use the DRB III and check the flow outputs of the injectors. check boost leaks as wasted boost from leaks means wasted fuel being sprayed. boost gauge will tell you if your waste gate is sticking open or closed also and hurting econ. I started off with 15 mpg with my cummins when i got it at 48K miles and went to town on the air flow stuff and got 24 mpg out of it with stacked tuners on max settings. air flowing in and out is the best way to raise mpg but start by checkin your guages, your injector flow rates, and airflow problems

 

[hoogkar]

I checked the jacobs brake and it is fine, I have a modified air box with bottom tube and vanes removed fron the turbo tube. the boost preasures are reading great but I do believe there has been a small increase in egt's.

I am getting a code P0477(exhaust pressure control relay low). I have added Magnaflow dual exhaust, but that was several months before this problem started. l

 

[LCrisp]

do you have any aftermarket egt or boost guages??? seeing in your signature that you have a jake brake. might it be starting to stick closed somewhat? use ur egt and boost gauges to diag lack of exhuast flow or lack of air for the fuel being sprayed. I know that in total all of my exhuast work has increased my mileage close to 3. 5 mpg but that may be compounded with the other mods that needed the flow. so there has to be severe negative effects on the engines efficiency when the jake brake is stickin. come to think of it thats what they were designed for to severely choke the efficiencies of our diesel air pumps. also to check injectors use the DRB III and check the flow outputs of the injectors. check boost leaks as wasted boost from leaks means wasted fuel being sprayed. boost gauge will tell you if your waste gate is sticking open or closed also and hurting econ. I started off with 15 mpg with my cummins when i got it at 48K miles and went to town on the air flow stuff and got 24 mpg out of it with stacked tuners on max settings. air flowing in and out is the best way to raise mpg but start by checkin your guages, your injector flow rates, and airflow problems

'05 5. 9 48RE, 3. 73 4wd, quad, stock
current best mileage is 18 @ 69MPH on cruise control.
I have never got into the gauges and all that.
Who would I have to take this to for this work?
I live in Vancouver, Wa. Alan