Low fuel mileage - Diesel Bombers



24 Valve 2nd Gen Dodge Cummins 98.5-02 Discussion of 24 Valve 5.9 Liter Dodge Cummins Diesels with VP44 Injection Pumps
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Old 08-27-2012, 07:29 AM
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help Low fuel mileage

Ok guys so my truck has turned into a dieselholic here lately it has been drinking diesel like its going out of style. Ive checked for fuel leaks and have found none the fuel filter has been replaced an air filter has been cleaned also. I just recently pulled the injectors an cleaned them an installed new copper washer an orings on the injectors an also replaced the orings on the connector tubes. What would be causing this thing to drink the fuel??? Also would a boost leak cause a dramatic drop in fuel mileage? Reason Im asking is bc Ive got what seems like a preaty good leak at were the turbo mounts to the exhaust manifold. Thanks for any help or advice
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Old 08-27-2012, 07:39 AM
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That leak could cause bad mileage for sure.

Unless your oil level is going up, the connector tube O-Rings are fine.
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Old 08-28-2012, 11:25 AM
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Ok so I got a new gasket for the turbo to manifold connection and got it installed an everything an there seems to be leaks. Is there anything else that I should look into or go over?
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Old 08-29-2012, 02:40 PM
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Originally Posted by redneck_cummins View Post
Ok so I got a new gasket for the turbo to manifold connection and got it installed an everything an there seems to be leaks. Is there anything else that I should look into or go over?
A bad torque converter. My 94 was getting 15-16 @ 60 mph. I replaced injectors, rebuilt the pump. A friend noted that the rpms moved more than he thought in lockup when he tramped on the pedal. we backed the tranny out for a look at the converter. It was discolored and he said a new converter would likely fix it. It did. Mileage on the next tank was 21. Make sure the valves are adjusted, new air filter . I assume it's not smoking and has good compression?
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Old 08-29-2012, 03:12 PM
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A bad torque converter. My 94 was getting 15-16 @ 60 mph. I replaced injectors, rebuilt the pump. A friend noted that the rpms moved more than he thought in lockup when he tramped on the pedal. we backed the tranny out for a look at the converter. It was discolored and he said a new converter would likely fix it. It did. Mileage on the next tank was 21. Make sure the valves are adjusted, new air filter . I assume it's not smoking and has good compression?
The OPs truck is a 5spd. How many miles are on it? When did you last adjust your valves? Check all the boots for rips/holes and make sure all the boot clamps are tight.
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Old 08-29-2012, 05:57 PM
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we had a customer that had a cracked manifold. almost didnt see it and really couldnt hear it. check around there and make sure. replaced with a 3 piece and bumped mileage up some for him. also see you have a edge, pull up tps percentage and set cruise, his also had a bad spot in the tps and it was constintly jumping up and down trying to maintain speed but couldnt fix on the spot it needed to so that killed mileage.
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Old 08-30-2012, 01:26 PM
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The truck just ticked over 200,000 miles and I adjusted the valve lash probably a month or two ago and set them at .06 intake an .16 exhaust iirc. Ive also replaced the tps with one from genos garage an set the voltage to .670, could the voltage be set to high causes fuel loss???
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Old 09-03-2012, 07:43 AM
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Depends on what the voltage said on it. Should set .02 or less under what it says if I remember right.

---AutoMerged DoublePost---

Also did you relearn it after replacing?

Last edited by mprmn08; 09-03-2012 at 07:43 AM. Reason: Automerged Doublepost
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Old 09-04-2012, 12:40 PM
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Yeah I relearned the apps after install and adjustment. I also redone my valve lash an set it back to .10 and .20. I talked to my uncle an he told me that having them set at .08 an .18 the valves probably wasnt closing all the way which he said would cause the motor to use more fuel. So I figured what the heck its free an all so I readjusted them to cummins specs. So we'll see how it does Thanks for all the replies an info guys
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Old 09-18-2012, 12:03 PM
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Well guys I thought I had this mileage problem fixed but turns out I dont I just put $70 in it Thursday an it put it right above 7/8 of a tank. Well now its setting right below 3/4 of a tank an Ive only put 88 miles on it. Does the mileage an fuel usage sound bout right??? It seems to me that it should do better than that. I dont run it hard an Ive got the smarty on the mileage setting. What would be causing this bastard to drink diesel. Im to the point Im tried of it nickeling an diming me to death. I really need help here guys I cant afford to keep putting $80/week in fuel

Last edited by redneck_cummins; 09-18-2012 at 12:33 PM. Reason: typing error
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