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View Full Version : 98 cummins mileage problems


LLOYDSTER
03-22-2008, 08:36 AM
hey guys, first time posting. wondering why I can only get 650 kms to a tank on my diesel. any recommendations? truck is all stock except for superchip. mileage is about same without chip. small crack in exhaust manifold. is my injector pump going? ther seems to be a good lag on certain days with the turbo as well. would a defective turbo cause that? how do I check that? what is a torque converter upgrade worth? cold air intake? would cleaning the injectoers help? truck has 155,000 kms. any info would be great. full tranny flush was just done cause last year towing trailer to beaver lake up hill it would overheat almost like tranny was slipping. love the truck just need cheapest way to figure out issues. where would you start?

HEAVY METAL
03-22-2008, 09:00 AM
[15] [15] [15] [15] [15]


" long time listener, first time caller here.."

sorry had too...[cheers]

bakelite
03-22-2008, 09:03 AM
What size is your tank? I get less than that with a first gen :dontknow:

LLOYDSTER
03-22-2008, 09:54 AM
sorry,tank is 100 litres to fill exactly when fuel light comes on. 98 24 valve

sj-x 500
03-22-2008, 10:29 AM
sounds like you gotta scan it for codes. cycle the key 5 times and read where the milage usually comes up, it'll tell you 2 sets of codes. if one is a p0216 i think, then your ip is gone.

put a pressure gauge on the lift pump as well, they tend to go and hurt the injection pump

Trooper
03-22-2008, 10:51 AM
Is it smoking anymore then normal? When is the last time you cleaned your injectors. Is your air filter dirty? You could try putting a tank of b40 through it, Then changing your fuel filter after.
your getting 15.38 per 100km. Thats not that bad. I only get 11 on my 4.2 diesel. I run either heating fuel or b100 in it tho.

sj-x 500
03-22-2008, 10:55 AM
i usually get about 900 for 110 liters... 01 auto, chipped, and piped

LLOYDSTER
03-22-2008, 12:52 PM
no more smoke than usual. no codes coming up on superchip. fuel filter done, air filter clean. maybe i'll do the injectors. what about the torque conv. upgrade?$$? I'll try the cycling the key as well. thanks keep the info coming guys! much appreciated! 650 kms is still too low for mostly highway!

sj-x 500
03-22-2008, 02:14 PM
are you sure the key flipping worked? it'll always tell you a code, or it'll say "done" ... odd that no codes would come up..

epic3
03-22-2008, 03:31 PM
is your accelerator pedal weighted?

sj-x 500
03-22-2008, 06:00 PM
fuel leaks?
brakes dragging?
check the tubes going from the turbo to the charge air cooler, and from the charge air cooler to the intake, i've had a hole rubbed trough the rubbers. they're nto cheap to replace, but you can get kits from peirsdiesel or bd diesel to change em all, or get one from a wrecker like i did. i've seen clamps come off and cause over heating conditions when towing.

78bronco
03-23-2008, 01:10 AM
just keep your foot outa it I got a 1st gen that gets 650km on 35's with stage DDP injectors and custom pump and hx40 turbo and a real heavy foot

LLOYDSTER
03-23-2008, 07:47 AM
nothing happened when I tried the key thing. sat there for about 15 minutes like a moron. do you have to wait till all the lights gfo out or is it a quick back forth part way or all the way? I will inspect the lines on the turbo today. clamps coming off where to cause overheating?

LLOYDSTER
03-23-2008, 09:30 AM
is it true that every diesel engine's mileage can fluctuate by as much as 2-300 km's per tank cause i've heard of a few guys who say it could just be the truck but I dont believe that. I have 3 buddies with new 07 5.9 cummins and they all get more than me even with the new emmission controls. is there anything on my 98 that would case that such as a cat or muffler prob? it all looks good from the underside. thouht my power would be better too with the chip. it goes but not like I think it could. assuming I probably need to put in the torque conv. upgrade

REDNECK-WELDING
03-23-2008, 09:57 AM
cycling the key dosent work on the 98s i believe. have you cleaned out your IAT and MAP senser? i did and got 3mpg more out of my truck. my friend who has a 98 did it and his milage went from 650-700 up to 850 a tank.. worth a shot on yours. it takes about 20min to do. let me know if you need the chart to locate them

Pete

LLOYDSTER
03-23-2008, 10:44 AM
no idea who what where when these sensors are. yes sire map please. and what do you needd to do this? sorry chart needed. tools? brush? thanx

LLOYDSTER
03-23-2008, 01:29 PM
could usethe chart to locate them please as well as what is required to do this.

sj-x 500
03-24-2008, 09:40 PM
if it's a 24 valve it should work seeing as it's obd2. it'll flash numbers right away.
there are no cats, a restricted muffler could do it, soot could build up and choke the flow, which would result in low boost and high egt. gauges help lots for trouble shooting low power and bad milage issues.

sj-x 500
03-24-2008, 09:43 PM
is it true that every diesel engine's mileage can fluctuate by as much as 2-300 km's per tank cause i've heard of a few guys who say it could just be the truck but I dont believe that. I have 3 buddies with new 07 5.9 cummins and they all get more than me even with the new emmission controls. is there anything on my 98 that would case that such as a cat or muffler prob? it all looks good from the underside. thouht my power would be better too with the chip. it goes but not like I think it could. assuming I probably need to put in the torque conv. upgrade


the early 07 5.9's use a common rail fuel system with unlimited fuel delivery timing. you can't compair a 24v which is a old school high pressure line from a pump to a nozzle system.. not very efficient. m 01 24v gets 900k - 100 liters. my dads 07 gets 1100k - 100 liters.

REDNECK-WELDING
03-24-2008, 10:38 PM
the ones you are looking for are #7 and 10 the IAT is 13/16s and the map is 1 1/6 both need to be deep sockets. mine is a 2000, yours might be a 1 1/4" they are located on the drivers side rearward part of the block. just past the fuel filter. hoep this works for you... let us know if it does

Kinslayer
03-25-2008, 09:11 AM
Only experience I have with em was going up to Kelowna this weekend in my paw's.. I had 700k on the tank with 3/8's left when we rolled back into the wack.. I hear you can get way better milage when using a K&N as well.

LLOYDSTER
03-25-2008, 10:16 AM
thanx for the huge response guys. may take a little time to investigate all the options. but i'll try and keep you posted. what is the time, labour and dollar amount associated with the torque conv. upgrade?

LLOYDSTER
03-25-2008, 10:18 AM
it is 24 valve by the way

kwast
03-25-2008, 08:48 PM
Key cycle trick doesn't work on '98s. mine does pretty good 18-23mpg on the highway hand calculated, depending on how fast I go up the canyon. those #'s are before the chip and 4".
The converter upgrade will get you some mpg as your stall speed will prolly drop 200rpm or more. My trans was built last year by a local trans guy (family friend) and was a general rebuild with an upgraded TCI converter and a Trans-go shift kit. It is the cheaper way to go (I think I was $3500 and change out the door) compared to say a new "bullet proof" trans from you know where. She shifts good and hard and locks up nice(I still wish it was a stick). My brother-in-law spent $6k plus on his "bullet proof" trans and he says mine feels stonger (although I've driven his and I think his is better lol) but he spent double what I did and I'm still covered for 2 more years even with my chip.

If you like to read you can check out this site you'll find almost everything you need to know http://www.dieseltruckresource.com/dev/index.php

Cookie
03-26-2008, 04:11 PM
i can get roughly 1000k to my tank when drivin fsj to chilliwack or visa versa. when im just toolin it round town and shit it goes down to about 750ish per tank.i dadded 4" exhaust and k&n. no chip and it gave me almost 25% better fuel economy.its a 12valve late 97