Update on 98 fuel mileage HELP!!!!

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The vacuum is caused by the lift pump to pull fuel out of the tank. The lower the tank gets the harder it is to get the fuel up to the lift pump the higher the vacuum the more intraned air. The souce of the vapor is the fuel itself. The lower the fuel more sloshed, have you ever watched when you fell your tank how much foam there is. Cummins acknowledges that diesel fuel entrains air,that the air collects in the fuel filter and then passes through . Caterpillar acknowledges that diesel fuel normally contains about 10% air in solution. Caterpillar,Cummins,Mack and Detroit Diesel state in their engine service manuals that air/vapor in the fuel system is a cause of low power ,engine suging, roughness and in general ,poor performance Just try it a couple of tank to see if it helps. Half tank and above.

 

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One thing I noticed that no one has asked, do you wear you lead shoes when you drive? If your like me, sometimes i leave them at the door on my way out, sometimes i leave them at the door after i get home. (This will seriously affect your milage). I also agree with Doug and the 1/2 tank,I try never to run below that amount be refueling.

 

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I really dont beat the **** out of the truck. My mileage is usually always the same--- By the time i hit 3/4 of a tank (on the mark) my mileage is always 120 give or take a few miles. And I always top off the tank completely so that it is full even in the neck. I always run the tank down low and usually put between 28 and 31 gallons on each fillup. That hissing sound after shutoff seems to be coming from the drivers side underneath but I will look into this further. I thought all that talk about those red caps back near the fuel tank was on newer trucks

[This message has been edited by RedNut (edited 11-13-2000). ]

 

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Rednut do you strictly drive in the city only? What i'm thinking is you my need to take a trip on a freeway or toll road and drive a couple hundred miles at 70+ miles an hour to clean out the engine. I have also used Pri-D to keep the clyinders cleaned out to cut down on black smoke and carbon build up,it works for me. While driving in city traffic i used it at every fill up,Do you use any additive like Stanadyne Performance Formula. I have also added a quart of B-12 to a tank of fuel to clean out the injector pump and it helped. Using these products is a personal preferance,use only if your comfortable with it.

 

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Could the hiss be the turbo comming to a stop?

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1972 Chinook class C with 96/215 5spd, 4/5" exh, 4"BD, MagHytec, 85gal fuel, K&N RE0880, AutoMeter, 370's, BD gov kit, BD afc kit, yada-yada-yada
www.fostertruck.com/cummins

 

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Larry how long does the turbo take to spool down after the engine is shut down?

RedNut, personnaly I do not think you are goin to get more then 15mpg in city traffic, remember you are pushing alot of basic weight, not including extra items such as tool box, etc.

[This message has been edited by BillTanziniSr (edited 11-14-2000). ]

 

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My mixed city/hiway miles is almost always pretty poor at around 12-15. Thats a 12 valver 2wd with an auto and 4:10 rears. If I just use the Ram for driving the kids to school and getting groceries, I never break 10. Get me out on those rural freeways though and I always hit around 22. Pulling a 15,000 5er I get 10-12 depending on terrain. Not too bad for a big truck.
-Paul R. Haller-

 

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My turbo sometimes takes up to 5sec to stop hissing. Its like a slight growl/grind combined with the hiss, gets quieter and finnaly goes away

 

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I get 17 mpg on the highway, 15 to low 16's highway city combined. From what I understand, I may be losing 1-2 mpg with the larger tires but I like em! 15 is nothing alarming to me. I also drive like a maniac. #ad


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John McEachern
Fort St John B. C. Canada
1998 12v, 4X4, QC, auto w/tc switch, air, tilt, cruise, 3. 55 gears, TST #6, Isspro boost/pyro/transmission gauges, BD VB&TC, CC industries headache rack and rails, JVC KD-SX949 Cd player, forest green,
Kelly Safari MSR 285 75 16, K&N airfilter.

 

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RedNut; I have a '96 automatic 4x4 2500 std cab and drive about 12 miles each way to work. 1/2 of this is stop and go and the other 1/2 is straight down the interstate. From day one in the winter it has been 15mpg and in the summer 17mpg. I think part of the reason it is lower in the winter is I run with the defroster either on or mixed with the floor vent. Plus there is a little more warm up time in the morning. The last long trip we took was about 700 miles long from Reno to home and with the cruise set never over 65mph it was 20mpg. Just my $. 02 worth

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96 2500 4x4 Driftwood auto Waren 4x boards pyro,boost,trans temp on a piller mag hytec trans

 

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Rednut I don't think you milage is so far off. I get empty about 15 to 17 mixed city hwy, and the best I can do on the open hwy is 17 to 19 max. Seem to go about 120 miles on a 1/4 tank. Pulling the 14k trailer I get about 10 to 12. My timing is set at about 16 degrees. You can see my signature for the rest.

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1996 4x4 3500 4. 10 5spd, Diesel Dynamics stage 2 injectors, #5 TST plate, Govoner spring kit, 16cm2 housing with 4" exhaust, Cummins exhaust brake, US Gear overdrive, Grover air horns, Mag-Hytec cover, and more.

 

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If you have your heater set to defrost,defrost and floor or an ac setting the hiss could be the pressure equalizing in the ac system.
Just a thought.

We have the same debates on mpg on the 24v forum too. The guys in the mountains vs the flatlanders, the urban dwellers vs the flatland farmers yada yada ...
every truck is different, every driver is different. city driving in Tulsa is diff than in Seattle. In Tulsa the lights are 1 mi apart and the city is chriscrossed and looped by freeways, Seattle has lights every 1/4 mi and 2 n-s freeways that move at 30 mph on a good day. Even the the same truck and driver will get diff mpg in theis settings.

[This message has been edited by JNutter (edited 11-18-2000). ]

 

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Could my starter be staying engaged???(just went this weekend after staying engaged for a few weeks after starting)

 

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My hwy mileage stayed around 20 to 21. If I went south on Hwy 395, thru 3 cities & the Sierras to Big Pine, 20. something mpg. Same from Reno to Hwy 1, N of San Fran on Hwy 20 to the coast. The last trip was this last weekend. It was North thru the mountains to Mt. Shasta to I5 & on up to the land of the Scourge.

The mileage stayed at 20. something until we hit the Oregon football crowd on the freeway. That one was down to the 17's, stop & go. Once @ BD, the Scourge group put in the 4200rpm Gov Spring Kit & the HX40-16 & the mileage on the trip back stayed @ the 22's mpg. #ad
#ad
#ad
Same driving speed, shifting, accelerating, etc.

Now comes the commute route where the norm was 17. something mpg.

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Money Sink - 96, 5 speed, HX40-16, TST #11/280 slid 3/4 way, 300 HP Injectors.
4" CAT back & CATless, 4" chrome turn down straight out back.
ISSPRO Pillar, Delvac 1 & Amsiol, K&N, Mag-Hytec, 3:54, 235s on Alcoas, Rancho 9000's, Valentine One.
Un-Bombed = Boring

 

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I normally get almost 19 mpg, mostly city driving in Denver. Never got below 18, and the highest is 21 mpg. I didn't notice any change going from 245/75-16's to 255/85-16's (~30" to ~33"). I did correct the speedo when I changed tires. The truck is stock except for the tires and a 2 1/2" front coil spacer.

Pete

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'97 2500 CC 4X4 5spd Sport
'83 K5 Blazer 350 TBI (ex 6. 2), 39. 5 TSLs, 3" lift, Dana 60/GM 14 blt, Detroits

 

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I get on aveage 17. 5 year round. My problem is I get better in town 18-19 on the road I get anywhere from 14-18 thats at 70-75 mph. Cant understand the big changes on the freeways, unless some stations sell crap for fuel.

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96 2500, 5 speed, Fuel preporator, K&N, Dr. performance injectors, Horton, No cat, Holes in muffler,and going broke with the price of fule.

 

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I once forced myself to drive 55 mph for several hours to check mileage in the central valley of CA. I filled up at the same pump before and after the test drive. I got 25. 8 mpg. That is only turning 1500 rpm with my truck. If you can stand to go that slow, the truck gets fantastic mileage. I normally get 18. 5 mpg at 75 mph commuting over a 1000' hill everyday.

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1998 2500 Quad Cab, 12V, 5spd, 4x4, HD Transfer Case, 370HP Diamond B Injectors, #4 TST, 16cm2 Housing, AFC Spring Kit, BD Governor Spring Kit and other modifications, Walker Muffler, 285/75-16 BFG AT's, Stainless Steel Tube Steps, Reese Fifth Wheel Hitch, Leather, CD, LSD Dana 80 Rear, 60 Front, Centerforce Dual Friction Clutch, Rancho RS9000 Shocks, Rancho Steering Stabilizer

 

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Dr Bob, you arent nuts. I get better miles around town too.
I believe the RPM's get a bit too high for good mileage on the open road. (75+ MPH)