LB7: Fuel milage

[torqued2dmax]

There are reasons why we want to know how long you owned the truck and how many times you limped it and what the truck i cc , ec , 8ft bed , allison or stick , if you dont give a good description of the truck no one will chime except for me because I am bored , but now I am going to bed because I am old ! And anyone can slap jb on a t pump , fill it with oil and sell it to you . Good night !

 

[zakkb787]

Did a little research because I’m bored. Seems that in some cases, it takes a few thousand miles for injectors to break in... saw a few people report poor mileage after injector change but eventually it came back up. Make sure you have no leaks. Be triple sure there’s no fuel smell anywhere at all under the hood. Make sure your balance rates are good. And keep your eye on your oil. If you’re not making oil, don’t smell fuel, and have no leaks, run a few tanks through it I guess.

Maybe Simeon who knows more will chime in. Just my .02. As far as the rattle. Where does it sound like it’s coming from?

 

[2004LB7]

Never heard of breaking in injectors

 

[DAVe3283]

So how many gallons went in? On my 2003, the stock pickup tube cracked and it would run out and die with 10 gallons left in the tank.

Get it filled up and calculate your actual mileage (ignore whatever MPG the dash shows, if yours has that feature). Mostly around town I'd expect 11-13 MPG. If you're in that range, nothing much you can do, really. I barely get 15 in town in my Suburban, which is lighter than the truck and on the stock tires with a 6 speed Allison conversion.

If you don't get as many gallons in as you expected, it might be worth putting a new sender in. It isn't bad to drop the tank, and removing the bed is even easier if you have 3 buddies (or 2 strong buddies).

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[zakkb787]

Never heard of breaking in injectors

Me either but some report it so might be something

 

[Jacob tomlinson]

I ran out of fuel just under a 1/8 of a tank, 25 gal tank, reason i ran out of fuel mostly is because ny leveler os going out and i have to replace it.

 

[Dozerboy]

It’s winter 12mpg doesn’t surprise me at all.


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[Hambone]

Winter fuel definitely affects mpg!
Who’s injectors?
Have you tested the balance rates?
Is you TC failing?
Fuel filter plugged?

 

[Jacob tomlinson]

Bosch reman injectors, no i have not tested the balance rates, how would you know it is faiking?? (Have a light grinding noise when i barely press the gas) mahbe thats the tc??, fuel filters new and fine.

 

[zakkb787]

Bosch reman injectors, no i have not tested the balance rates, how would you know it is faiking?? (Have a light grinding noise when i barely press the gas) mahbe thats the tc??, fuel filters new and fine.

Need to plug it to a diagnostic machine. Check balance rates and might as well check rail pressure vs desired rail pressure while you’re there. Grinding could be trans. Could be just about anything. Might want to get one of your buddy’s to get beside the truck and see if they can pinpoint about where it’s coming from. You need to do a sump for your fuel. And a lift pump.

 

[Jacob tomlinson]

Need to plug it to a diagnostic machine. Check balance rates and might as well check rail pressure vs desired rail pressure while you’re there. Grinding could be trans. Could be just about anything. Might want to get one of your buddy’s to get beside the truck and see if they can pinpoint about where it’s coming from. You need to do a sump for your fuel. And a lift pump.

Im saving for the fuel pump there kinda pricey

 

[Firefightkev]

Check the tcase for fluid and metal flakes. I kept hearing a noise that I couldn't figure out. It turned into a grinding noise that would increased on tc lockup. It didn't start leaking fluid till it came out the front drive shaft seal.

 

[DAVe3283]

You don't need a sump or fuel pump to get good mileage. A lift pump can br nice, but a sump isn't necessary. It would solve your problem of running out of fuel at 1/8 tank, but you can also replace the factory sender and be good to go for 10+ years.

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[torqued2dmax]

FIND OUT WHAT THE GRINDING NOISE IS , FIRST !!! Jack up the rear , use jacks and jack stands , put someone you dont like under it, run slowly through the gears to about 40 mph slowly step on brake put in park , fix the problem !

 

[zakkb787]

You don't need a sump or fuel pump to get good mileage. A lift pump can br nice, but a sump isn't necessary. It would solve your problem of running out of fuel at 1/8 tank, but you can also replace the factory sender and be good to go for 10+ years.

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That’s why I said get the sump to get rid of the 1/8 tank issue. Sump is probably cheaper and more reliable if done right than sending unit.

 

[Dozerboy]

What does a sending unit and a sump have to do with running out of fuel? One had nothing to do with the other. Either his fuel level sensor/gauge is messed up or he has a hole in his pick up tube.


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[zakkb787]

What does a sending unit and a sump have to do with running out of fuel? One had nothing to do with the other. Either his fuel level sensor/gauge is messed up or he has a hole in his pick up tube.


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Uh... would a bad sending unit not cause the truck to run out of fuel like the 1/4 tank issues with these trucks? And would a sump not fix this?

 

[OregonDMAX]

Getting a sump to fix 1/4 tank issues is opening yourself up to bigger problems... You shouldn't be letting the tank get down past 1/4 tank it's bad for the cp3 plain and simple.

 

[DAVe3283]

Getting a sump to fix 1/4 tank issues is opening yourself up to bigger problems... You shouldn't be letting the tank get down past 1/4 tank it's bad for the cp3 plain and simple.

I run my LB7s to the fuel light every time. My truck's original CP3 (290,000 miles) was only replaced because I went to a 12mm stroker when I built the motor. Suburban has the original still.

Between the truck and Suburban, I've run out of fuel 5+ times (cracked fuel pickup tube and calibration issues from the swap respectively). No problems so far.

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[Dozerboy]

Uh... would a bad sending unit not cause the truck to run out of fuel like the 1/4 tank issues with these trucks? And would a sump not fix this?

A bad fuel level sensor isn’t going the be fixed by installing a sump.

I’m not a fan of sump anyways and agree that you shouldn’t be running your tank so it has much less the 5gal in it regularly.


Damn we are off in the weeds. This ones about mileage... lol


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