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Discussion Starter · #1 ·
I have a 2001 7.3ps 4x4 auto. 3.73rear. And stock tires. Mods/50hp tune,k&n air intake. I have heard that i should average around 14-20mpg. I get maby 240m on 1 tank( about 9mpg) on hwy. and about 4-8mpg in town. It runs great,dosent smoke,starts easy,builds boost 1-4psi at 1500rpm. And has no codes. I cant seem to find how to fix this. I love my truck but with this current inflation it kinda sucks. Is this normal? Please help -thanks tyler slay
 

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You should be seeing around 5 psi boost at highway speeds on level ground. How high does it get when you actually put a load on it. If you can't get it up to around 12-14 psi when you accelerate up a fairly steep hill.
Are you calculating mileage manually, or using the overhead display. The latter can be wildly wrong with a tune loaded.
Could be you have an exhaust restriction (Exhaust Back Pressure Valve partially closed.)
 

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Don't completely dismiss the idea. You can have pressure and still have a leak. After I did my 250K "rebuild", I noticed some oil stains on the spyder right where it joins the turbo. I took that clamp loose and noticed about a 3° misalignment. The clamp (worm style) actually was missing a tooth as well. New o-ring and new clamp installed and no change in boost, but my MPG went up from 17.3 to 20.1 hand calculated. It's super easy to build a boost leak detector and find even the smallest leak.

Other MPG killers - bad fuel pressure (dirty filter / tank pick ups), dirty air filter, clogged EBP sensor tube, broken MAP sensor hose, dragging brake calipers, and a bunch of others.
 

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Discussion Starter · #6 ·
Don't completely dismiss the idea. You can have pressure and still have a leak. After I did my 250K "rebuild", I noticed some oil stains on the spyder right where it joins the turbo. I took that clamp loose and noticed about a 3° misalignment. The clamp (worm style) actually was missing a tooth as well. New o-ring and new clamp installed and no change in boost, but my MPG went up from 17.3 to 20.1 hand calculated. It's super easy to build a boost leak detector and find even the smallest leak.

Other MPG killers - bad fuel pressure (dirty filter / tank pick ups), dirty air filter, clogged EBP sensor tube, broken MAP sensor hose, dragging brake calipers, and a bunch of others.
I did a turbo leak test not to long ago and i have no leaks that i am certain. But a dirty fuel filter is a possibility. And maby low fuel pressure. How can i check the fuel pressure
 

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Discussion Starter · #7 ·
Don't completely dismiss the idea. You can have pressure and still have a leak. After I did my 250K "rebuild", I noticed some oil stains on the spyder right where it joins the turbo. I took that clamp loose and noticed about a 3° misalignment. The clamp (worm style) actually was missing a tooth as well. New o-ring and new clamp installed and no change in boost, but my MPG went up from 17.3 to 20.1 hand calculated. It's super easy to build a boost leak detector and find even the smallest leak.

Other MPG killers - bad fuel pressure (dirty filter / tank pick ups), dirty air filter, clogged EBP sensor tube, broken MAP sensor hose, dragging brake calipers, and a bunch of others.
Also i can count of air filter as it is brand new. But today ill see about changing the ebo sensor tube
 

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To check fuel pressure, you need an adapter that fits into the back of the fuel bowl. Here's an example - #13-001 Pressure Port Adapter - Straight 1/8 FNPT

I personally believe a permanent fuel pressure gauge is one of the more important things to have.

Also, if you don't have one, get a scanner that can read PIDs on a powerstroke. Autoenginuity with the Ford enhancement, ForScan (available on iOS, Android, and PC), or even get a ScanGuage. I have the ScanGauge permanently mounted and watch my current and trip MPG constantly. That way, I can adjust my driving habits to achieve maximum efficiency. It's kind of fun to "hypermile" an 8000-pound truck.
 

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Discussion Starter · #9 ·
To check fuel pressure, you need an adapter that fits into the back of the fuel bowl. Here's an example - #13-001 Pressure Port Adapter - Straight 1/8 FNPT

I personally believe a permanent fuel pressure gauge is one of the more important things to have.

Also, if you don't have one, get a scanner that can read PIDs on a powerstroke. Autoenginuity with the Ford enhancement, ForScan (available on iOS, Android, and PC), or even get a ScanGuage. I have the ScanGauge permanently mounted and watch my current and trip MPG constantly. That way, I can adjust my driving habits to achieve maximum efficiency. It's kind of fun to "hypermile" an 8000-pound truck.
As soon as i get off work im going to, clean/replace the ebp hose. I will change fuel filter, and inspect brakes,drivetrain,and add injector cleaner to the fuel bowl. I will look about getting a fps gauge. What is normal fuel pressure?
 

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Minimum fuel pressure per Ford is 35 psi, but optimum is 65 psi. It shouldn't fall much at all when under load.
 

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My lifetime average is right around 15 mpg. Has been as low a 6 mpg driving into a headwind with a camper on and trailer behind, but yes, you should get better than 10 mpg.
 

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My lifetime average is right around 15 mpg. Has been as low a 6 mpg driving into a headwind with a camper on and trailer behind, but yes, you should get better than 10 mpg.
Changed fuel filter, cleaned ebp. Went on a trip out of town not far about 110miles. Empty truck,full tank of diesel, and cruised 65mph the whole way non stop(1800rpm and about 7psi avg boost) i consumed just a little over half a tank. Im more than likely going to half to fill up to get back :(
 

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You can't figure out fuel economy by going by the gauge.

If you could do that I'd be getting 40-50 mpg on one half and 5 mpg on the other half, you need to do the math by dividing the miles driven by the fuel used.

This is presuming that your odometer is calibrated to your tire size and is correct.

Sent from my SM-J737V using Tapatalk
 

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Discussion Starter · #15 ·
You can't figure out fuel economy by going by the gauge.

If you could do that I'd be getting 40-50 mpg on one half and 5 mpg on the other half, you need to do the math by dividing the miles driven by the fuel used.

This is presuming that your odometer is calibrated to your tire size and is correct.

Sent from my SM-J737V using Tapatalk
That’s exactly what i do! The over head display was stolen out of my truck about 5ish years ago. Just did the math. I got [email protected] 65mph. Makes no sense! I have zero blow by no brakes hanging my tires are stock i drive easy engine idlesgreat and runs better. Never seen smoke and has a new k&n air intake,new fuel filter, new oil and i just cleaned the ebp tube and sensor. Has zero codes!
 

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I personally believe a permanent fuel pressure gauge is one of the more important things to have.
RT is way ahead of me on the learning curve, I took his advice in 2018- and I completely agree on the importance of a permanent fuel pressure gauge as a diagnostic tool.


i have some major exhaust leaks, at the exhaust manifold to up pipe and up pipes to collector and I still have OK boost and still get good mileage (avg. 17 empty and 15 pulling 3500# boat/trailer) so I’m not sure that’s you’re issue.

I didn’t notice if it was mentioned - how many miles on the clock?

Up to date on periodical maintenance? Changing gear lube in differentials, checking wheel bearings, checking brake caliper slides and pads for drag?
 

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I just seen where you say that you are pushing 7psi of boost, that sounds high to me for driving at 1800 rpm.

While my truck is 96 I am only running around 2 psi of boost at 70 at around 2100 rpms with 4:10 gears. This is on a flat road.
 
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Discussion Starter · #18 ·
RT is way ahead of me on the learning curve, I took his advice in 2018- and I completely agree on the importance of a permanent fuel pressure gauge as a diagnostic tool.


i have some major exhaust leaks, at the exhaust manifold to up pipe and up pipes to collector and I still have OK boost and still get good mileage (avg. 17 empty and 15 pulling 3500# boat/trailer) so I’m not sure that’s you’re issue.

I didn’t notice if it was mentioned - how many miles on the clock?

Up to date on periodical maintenance? Changing gear lube in differentials, checking wheel bearings, checking brake caliper slides and pads for drag?
May be hard to believe but she only has 84kmiles. I change oil every 5k miles along with constant maintenance! Im a mechanic so im always paranoid about my vehicle make sounds i think i hear. Im not rich but if i feel a component is failing ill due my best to replace it. Last summer i was getting around 12mpg if i was lucky. Ive got to say its a great truck if it was costing me a fortune to drive!
 

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Discussion Starter · #19 ·
I just seen where you say that you are pushing 7psi of boost, that sounds high to me for driving at 1800 rpm.

While my truck is 96 I am only running around 2 psi of boost at 70 at around 2100 rpms with 4:10 gears. This is on a flat road.
I live in the hill country and i have a engine management computer. It says i avg 7psi boost . But on a flat ground i stay around 4-5
 

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she only has 84kmiles.
Nice!

Is this issue with the mpg something that changed at one point, or has the truck always had poor fuel mileage since you’ve owned it?

Have you removed the tuner and ran stock to see if it affects the mpg?
 
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