Poor fuel economy - Chevy and GMC Duramax Diesel Forum
Maintenance Discuss scheduled maintenace, capacities, filter part numbers, etc.

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post #1 of 23 (permalink) Old 05-16-2017, 09:03 PM Thread Starter
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Poor fuel economy

Hi I have a 2004 Silverado 3500 lb7

Recently had a huge drop in fuel economy. No mods pretty much stock.. typically I get about 575 to 600 miles per tank when not under load. About 375 to 500 under load depending on terrain, weight and weather.. I travel from. Phoenix to San Jose frequently .. recently on this route I have experienced a drop in mpg.. towing a 10k trailer on that route I typically get 425 miles out of a tank recently it cost me 210 dollars to go 562 miles. Three tanks of gas to go 562 miles..at this point it does not need to be hand calculated as I know the mileage from point a to point b and before I got there on a tank and a quarter not it takes 3 tanks.. had a injector pump replaced recently due to a fuel leak this helped for a few days.. recently started smoking at idle then under acceleration until I got to cruising speed after that smoking stopped but the poor fuel economy continued.. I ran injector cleaner through it and smoking stopped but still smells strong and get poor mileage.
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post #2 of 23 (permalink) Old 05-16-2017, 09:11 PM
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Does the truck have a CELL? Maybe it's time for some new injectors.


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post #3 of 23 (permalink) Old 05-16-2017, 09:17 PM Thread Starter
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What is a. Cell
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post #4 of 23 (permalink) Old 05-16-2017, 09:24 PM
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He means "CEL" check engine light. And unfortunately it sounds like injector time.

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post #5 of 23 (permalink) Old 05-16-2017, 09:25 PM Thread Starter
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Originally Posted by HD Dmax Machine View Post
Does the truck have a CELL? Maybe it's time for some new injectors.
I had it hooked up to a scanner and most of the injectors idled at 0.38 to 0.
42 however injector #7 was at 0.00
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post #6 of 23 (permalink) Old 05-16-2017, 09:26 PM Thread Starter
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No check engine light..
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post #7 of 23 (permalink) Old 05-16-2017, 09:26 PM Thread Starter
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Can I rebuild them??
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post #8 of 23 (permalink) Old 05-17-2017, 06:20 AM
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I would say injectors also.When was the last time your fuel filters were changed,oil,total maint?

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post #9 of 23 (permalink) Old 05-17-2017, 06:25 AM
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Quote:
Originally Posted by Frankfrein1235 View Post
I had it hooked up to a scanner and most of the injectors idled at 0.38 to 0.
42 however injector #7 was at 0.00
If those numbers are right you should be good on the balance rates. +- 4 is the spec, yours are all under 1 which is great. If I were you I'd be looking into other problems as well. Look for any signs of a boost leak or anything that might not have been installed properly when the injection pump was replaced.

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post #10 of 23 (permalink) Old 05-17-2017, 06:34 AM Thread Starter
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Fuel filter and air filter and oil about 1 week ago .
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