Looking for a cheap Auxiliary Fuel Tank solution

[dave_erald]

I just converted it, says my 6.2 Diesel is getting 12 mpg

Dually, unlocked 4l80(haven't gotten around to fixing that) 4.10 gears and 33" tires

If that puts anything in perspective, your big block unloaded should get close to that or better wouldn't it?

 

[Christian Steffen]

Last time I did the calculations, my trucks averaged 13 to almost 13.5 with the cruise set at 55, mainly open country driving, and on the day I brought home I managed to get about 14 with the CC set at 70;

My dad's C3500 gets 10 regardless.

That's really not too bad, at least for what it is. I have a friend with a gutless 1998 ford expedition that gets worse mileage than my all the time, so I really don't complain about it haha.

Is that 3500 a dually? I know the extra drag and inertia from the extra tires will make it worse, but I wouldn't think it would be that bad.

 

[BowtieBrody]

That's really not too bad, at least for what it is. I have a friend with a gutless 1998 ford expedition that gets worse mileage than my all the time, so I really don't complain about it haha.

Is that 3500 a dually? I know the extra drag and inertia from the extra tires will make it worse, but I wouldn't think it would be that bad.

Yup. 4.56 gearing too,

 

[Tom P]

Ah that's not so bad then. I just saw that 5.1 that you posted earlier and my eyes about popped out of my head!

No the only time I get that low of an average is with my Bluetooth scanner hooked up and that's what's doing the calculations.

I just converted it, says my 6.2 Diesel is getting 12 mpg

Dually, unlocked 4l80(haven't gotten around to fixing that) 4.10 gears and 33" tires

If that puts anything in perspective, your big block unloaded should get close to that or better wouldn't it?

Nah a 6.2 will always beat a big block in fuel mileage.

 

[Black_cirrus]

Well I'm pulling my 24' enclosed across the country this week I'll find out what it gets for mileage. Using the burb with 42 gallon tank and 454....

 

[Christian Steffen]

I'm not sure I would take what your scanner provides as gospel, if everything is how the computer thinks it should be the readings will be off.

For example, if fuel pressure is messed up and fuel trims are adding a bunch, your mileage will appear worse than it actually is, according to the scanner.

To calculate mileage, I'm sure they're using injector flow rate, injector duty cycle, rpm and speed, but this doesn't account for fuel trims. So if they injectors aren't flowing as much fuel as the computer thinks they are, and trims are making up the difference, the mileage reported will be worse.

 

[Tom P]

Yes that is one thing about this engine that they really messed up by not putting a fuel pressure sensor on the rail. It would have given the OBD a lot more tools to work with.

My fuel trims are more normal now, but I've disconnected the battery and held the cables together a couple of times in the last two weeks to swap black boxes so it's possible things are still low from that.

I think I'm going to bite the bullet and buy my own fuel pressure tester. The truck started almost normally this morning and idled perfectly so whatever I did yesterday put me headed in the right direction. The spark that jumped the first time I used the jumper wire made me think there might have been some kind of short in the system or maybe an issue with the ground. The several times I used the jumper wire afterward there no such sparks. Perhaps forcing it to work cleared up the issue. Makes me think though, that it is at best a temporary fix.

 

[BowtieBrody]

Huh. Damn shame it appears these guys don't make anything for the GMT400s,
https://www.transferflow.com/fuel-tanks/replacement-tanks

I started thinking, they make tanks for the GMT800; I wonder if one could be slightly modified to run on a 400?
Anyone got an NBS 2500 they could take measurements and compare to a GMT400 to see if anything would line up?

 

[Christian Steffen]

Yes that is one thing about this engine that they really messed up by not putting a fuel pressure sensor on the rail. It would have given the OBD a lot more tools to work with.

My fuel trims are more normal now, but I've disconnected the battery and held the cables together a couple of times in the last two weeks to swap black boxes so it's possible things are still low from that.

I think I'm going to bite the bullet and buy my own fuel pressure tester. The truck started almost normally this morning and idled perfectly so whatever I did yesterday put me headed in the right direction. The spark that jumped the first time I used the jumper wire made me think there might have been some kind of short in the system or maybe an issue with the ground. The several times I used the jumper wire afterward there no such sparks. Perhaps forcing it to work cleared up the issue. Makes me think though, that it is at best a temporary fix.

That is strange that it seems to be working correctly now. Maybe slapping it around made it decide to work for a bit longer haha

I agree, if it is working correctly, it feels like borrowed time.

 

[Supercharged111]

These trucks don't need fuel pressure sensors. Even if they knew, they wouldn't be able to do anything about it. The injector flow values are based on fuel pressure, so all you really need to do is hook up a gauge to know everything is OK. You can rent them from the parts stores.