only 14mpg

[danieljones]

I have done a few mods as my sig suggests but from what I have read I should be getting ALOT better mileage then I am. I do not have a heavy foot and I don't tow hardly anything but my boat during the summer. I need to adjust my valves but what else couldI do? Could my transmission be causing my mileage problem it is bone stock and it does seem to slip a little but just in first gear and only when you really stomp on it? I seem to have some what of a fast idle but it doesn't seem that bad. I live in the Portland Or area and if any body knows a good shop that I could take it to for a "tune up" lack of a better word.

Thanks for all that post.

Dan

 

[danieljones]

up:--) nobody knows??????????????

 

[paccool]

Dan, I'll try to help here.



When you set the pump to 15, did you check top dead center of the timing pin? Mine was off 2. 5 degrees. Made a difference in how the engine ran when it was corrected.



Make sure there are no air leaks in the intake system hoses, make sure the air filter is clean. What kind of boost numbers are you getting?



Check your exhaust system to see if there are any crimps or flat areas that may be causing back pressure. (boost would be low here as well)



Could be a problem with the injectors but that would show up as a low power problem. (how does the truck run?)



The problem has to be in the engine area. Pump would be the item I would suspect the most.



Are you sure the odometer is reading right?

 

[danieljones]

thanks for the responce paccool,

the truck runs well but I haven't driven any other diesel besides a 24valve.

getting aroung 30 psi WOT max egt's 1050



how would one go about checking for leaks?? ether around the joints?



exhaust looks good and I also replaced the turbo about 2 years ago



I didn't check the pin but before I did any mods the milage has been the same



don't want to throw 1200 at a pump if I don't have to.



thanks

Dan

 

[paccool]

Well, with 30 PSI boost, you just threw most of my thoughts out the window! Can't be air or exhaust with that kind of number. What about mileage before you installed the 12cm turbo housing?



Hey Bushwacker, any ideas on this one?

 

[Nordby]

What gears - is it a dually as well?

An auto an 4. 11's, driven at 75mph, is going to kill mpg (if you are driving that fast).

If you are doing 60-65mpg, driving easy, I think that is low as well. Should be 16-18mpg empty.

jon.

 

[Bob Beauchaine]

I'm running 3. 54's and my last fill shows 20. 01 mpg for about 1000 miles. You can see by my sig what I am running. What Nordby says about 4. 11's and dual rear tires will have some bearing on your mileage but you should still be at 17 to 18 mpg. Do you fill your own truck or do you let the pump jockeys do it? I always fill my own and try to fill up at Flying J in Troutdale. I would suggest finding a measured 5 mile run and compare your speedo to that. That way you know if what your seeing is accurate. 30 lbs of boost can be due to heavy fueling. As I have improved my performance and my trucks breathing my boost has gone down. Right now it is only about 17 to 18 psi - and you can see what numbers I am running. All in all though with all my mods I have always improved both performance and mileage - except when towing my 8000 lb trailer.

Bob

 

[BushWakr - RIP]

Yup, auto with 3:54's in decent shape (transmission) should be around 17/18/19 mph US.



You're pushing that 12cm to near it's limits at that boost, in my opinion, but what do I know . .

You can run the starwheel up a couple turns, easy back on the diaphram to perhaps 75% or so, and check again on a full tank of fuel.

After that, it's time to look at the "full fuel screw".

I found the most noticable differences when I adjusted the diaphram. (within reason)

I could change my around town light to light mileage by as much as 3 mpg with the diaphram alone.



Raising the starwheel up will hold your heavier fueling off a bit longer, allowing the PW's to do the work initially, then if you push it harder you will have heavier fueling come on. Just the delay of holding off a bit later should help some as well. .



Bob.

 

[Diesel Nut]

Timing is the big thing I would check. Also, if transmission is slipping alot then mileage go through the floor. My 93 had a bad tq converter because the guy before me thought it was a good idea to run an exhaust brake with an auto with no lockup converter. Wasted the converter. with that mileage, good possibility. Make sure also that your fuel lines aren't leaking. Otherwise, ya got me!

 

[danieljones]

thanks to all for the responses



I have 3. 54 gears and it is not a dually, maybe I did turn the screws a little too tight I don't really know I have turned a lot of wrenches but they have been on gas engines, diesel is a foreign language to me.



Bob you are in the Portland area maybe I can meet up with you sometime I could use some expertise in this area



I was under the impression that the more boost the more power guess I need to read some more



so should I go back to stock settings and start there? I am afraid I will miss what I have now but I will go hit the freeway for 5 miles and let you all know



THANKS FOR THE HELP

 

[JStoll]

I recently calculated myt milage at 14. 5MPG floging it

I think this is great Im running 4:10s & weigh about 9500 lbs

I am verry happy with this I wonder if a set of PWs will help it even further



-----------------------------------

89 D350 11foot C&C de kinked exhaust turned up timing getrag & 4:10s

 

[Bob Beauchaine]

I have always felt that it's the right foot that contributes most to mileage - good or bad. My mileage improved when the PW's went in. In fact I took an 11,000 mile cross country trip right after and got the best and worst mileage. Worst was 9. 9 towing into a 35 mph head wind in Iowa - best was 23. 56 non tow in upstate New York. When I am on the road I use my cruise control as much as possible - unless of course I feel like embarasing someone - going up hill. BTW my truck weighs in at 7000 lbs loaded and ready to go.

Bob

 

[Midnite]

Bob,



I always thought my right foot was the most important consideration as well--up until recently that is! On a trip to Fairbanks (about 380 miles one way from Anchorage, I think) I tried different driving styles and came away more confused than before.



(Truck is loaded with an 8', non-cabover pop-up style camper; loaded weight about 8200 lbs. )



When we left Anchorage, I drove pretty aggressively, with an average cruising speed of about 70 -75 mph and passed quite a few people (full throttle for several seconds, maxing out at about 90mph). When we refueled I figured my milage at about 14mpg.



When we left Fairbanks on the return trip, I drove at a very relaxed pace, passing almost nobody and with an average cruising speed of about 60 - 65mph. When we refueled I figured my milage at about 14mpg.



It's pretty much the same story unloaded (w/o camper), except my milage goes up to about 18. 5, regardless of speed or driving style (assuming mostly highway driving--lots of stop-'n-go traffic does drop the milage). It doesn't seem to matter how I set my highway cruising speed, or driving style.



I've noticed many other people on the TDR seem to experience the same pattern, but I can't imagine what might account for it. 4wd, 2wd, club cab, regular cab, long bed, short bed, none of those details have been consistent from what I've seen. Oh well... . my brain hurts--I'm going to have a beer.



Mike

 

[CAROLINA CUMMINS]

For most of my driving, empty and nailed to the wall I still get around 17-18mpg. And my pump is pretty much cranked full on, Can you say SMOKE

 

[JStoll]

I think with more weight the pump plungers efective stroke is kept longer for a longer period of time (the weights & spring take longer to eqquilize) ? whereas with an unloaded truck to maintain the same speed less stroke is needed to maintain the same rpm?

I dont know just my 2 cents

JAK

 

[AlK]

With low boost the truck will get better mileage. You can test this by simply setting the cruise control at a given speed and then watch the boost gauge, as soon as the vehicle goes up or down on a hill the boost gauge will respond accordingly. I would agree that 14 mpg is on the low side.

---

Al