7.3l mpgs cut in half

[Lurch830]

I've been towing for the last few hundred miles so I didn't notice it, but I dropped the trailer yesterday and burned a 1/4 tank in ~50 miles which close to half of what it typically does. Trying to get opinions on what to check since I cannot find any leaks and there are no puddles.
I'm leaning towards stuck/bad injectors, but any advice is appreciated! FYI - injectors are stock as far as I know and the truck has 185k miles on it.

Thanks,
Brandon

 

[Brud720]

I've been towing for the last few hundred miles so I didn't notice it, but I dropped the trailer yesterday and burned a 1/4 tank in ~50 miles which close to half of what it typically does. Trying to get opinions on what to check since I cannot find any leaks and there are no puddles.
I'm leaning towards stuck/bad injectors, but any advice is appreciated! FYI - injectors are stock as far as I know and the truck has 185k miles on it.

Thanks,
Brandon

Stuck open injector on a 7.3 you'll see white smoke out the tailpipe and it will run rough especially under load. Is it making oil? Turbo boost leaks? HPOP getting weak and not keeping Rail pressure to spec? Hows it on power?

 

[77GreenMachine]

Boost leaks or leaking fuel filter housing would be my first checks

 

[Lurch830]

Stuck open injector on a 7.3 you'll see white smoke out the tailpipe and it will run rough especially under load. Is it making oil? Turbo boost leaks? HPOP getting weak and not keeping Rail pressure to spec? Hows it on power?

It is not making oil & I cannot feel any boost leaks...granted its in neutral & only revved to 2k so not much boost to leak. Feels fine on power & doesn't seem like its idling rough either so I think the HPOP is fine?

Boost leaks or leaking fuel filter housing would be my first checks

I cannot see a leak at the fuel filter housing either, but it may only happen under load?


Gonna give it through the weekend to keep troubleshooting & maybe try to reseal the HPOP and/or fuel filter housing/drain...but I may have to bite the bullet & take it somewhere.

 

[77GreenMachine]

It is not making oil & I cannot feel any boost leaks...granted its in neutral & only revved to 2k so not much boost to leak. Feels fine on power & doesn't seem like its idling rough either so I think the HPOP is fine?


I cannot see a leak at the fuel filter housing either, but it may only happen under load?


Gonna give it through the weekend to keep troubleshooting & maybe try to reseal the HPOP and/or fuel filter housing/drain...but I may have to bite the bullet & take it somewhere.

If it were leaking fuel you'd smell it and see residue. Its possible you got a bad batch of fuel this tank?

I always track mileage per tank. If I have one that's real bad I make note of it but if the next tank or 2 are consistent that's when I start looking for an issue. It's good you noticed, but might need to track consistency first or we might all be on a wild goose chase lol.

 

[Croatan_Kid]

You need a scanner or monitor to really be able to see any of this stuff. They'll show you HPOP pressure, boost, and several other Ford specific values.

Boost and EGT gauges should, at minimum, be on anything diesel. EGTs high and boost low? Air problem. EGTs low and boost low? Fuel problem. Your tailpipe is also a valuable diagnostic tool.

I cannot feel any boost leaks...granted its in neutral & only revved to 2k so not much boost to leak. Feels fine on power & doesn't seem like its idling rough either so I think the HPOP is fine?

It'll make zero boost if it isn't under a load.

Usually, and very similar to a CP3 on a common rail diesel, when they (HPOPs) are headed out or have wear, hot starts will take a lot longer. All the worn stuff expands and fuel/oil leaks are exacerbated. Sometimes they're bad enough that they won't start until they've cooled down.


180-200k is usually a good time for a new set of injectors on an oil fired setup. They may not be hanging open, but they've usually got some wear in the nozzles.


Have you changed the oil recently? Is the alternator always charging at or above 13.8 volts? These trucks can have weird issues just from simple things like oil and alternators!

 

[1-tonmudder]

EBPV stuck halfway open/shut.Sensor might be bad,Long shot but how are your brakes/wheel bearings??

 

[Lurch830]

If it were leaking fuel you'd smell it and see residue. Its possible you got a bad batch of fuel this tank?

I always track mileage per tank. If I have one that's real bad I make note of it but if the next tank or 2 are consistent that's when I start looking for an issue. It's good you noticed, but might need to track consistency first or we might all be on a wild goose chase lol.

Possibly. Previous 2 tanks were from Buc-ee's in SC, the one before that & the most recent one were from the same station I typically fill up at in Asheboro. I will admit that the most recent fill up (Sunday) I pushed it too far and the truck started stuttering so I pulled into a parking lot, killed it & walked the 0.7 miles to get fuel & a 2 gal container. I do smell fuel when standing at the grill and there is residue in the valley, but its more like a film not standing wet with fuel. I generally track 16-18mpg depending on how heavy I am & 12-15mpg towing. Noticed it lower than normal coming back from SC and thought it could be due to speed, but it has gotten worse.

You need a scanner or monitor to really be able to see any of this stuff. They'll show you HPOP pressure, boost, and several other Ford specific values.

Boost and EGT gauges should, at minimum, be on anything diesel. EGTs high and boost low? Air problem. EGTs low and boost low? Fuel problem. Your tailpipe is also a valuable diagnostic tool.



It'll make zero boost if it isn't under a load.

Usually, and very similar to a CP3 on a common rail diesel, when they (HPOPs) are headed out or have wear, hot starts will take a lot longer. All the worn stuff expands and fuel/oil leaks are exacerbated. Sometimes they're bad enough that they won't start until they've cooled down.


180-200k is usually a good time for a new set of injectors on an oil fired setup. They may not be hanging open, but they've usually got some wear in the nozzles.


Have you changed the oil recently? Is the alternator always charging at or above 13.8 volts? These trucks can have weird issues just from simple things like oil and alternators!

I have an Edge programmer that I got for the integrated gauge pod. I haven't noticed much of a change in EGT or boost from normal. If I've got to get it scanned, I'll probably have that shop t/s & fix. I agree on the gauges...the truck I'm borrowing to get back home only has water temp & fuel level...I would think oil pressure would be a must have on anything! No issues with cold starts or hot starts. I was hoping to get the injectors to 200k, but when I first noticed the drop in mpgs my google-fu returned 150-180k which sent me down that path which made me think of upgrading the injectors & turbo. When I checked the oil I noticed it was a touch low, but the last change was done 4.8k miles/4 months ago & I was planning on changing it again this week. Alternator stays at 13.8V @ idle and 14.1V with rpm.

EBPV stuck halfway open/shut.Sensor might be bad,Long shot but how are your brakes/wheel bearings??

Possibly, any way for a shade tree mechanic to check the EBPV or sensor(s)? Brakes & bearings were good when I rotated tires last @ 180k in September and all the hubs on the trailer & truck felt cool to the touch while towing.

 

[77GreenMachine]

I noticed a significant decrease in mileage from Bucees. I have also consistently tracked a decrease from Sheetz

 

[1-tonmudder]

Possibly, any way for a shade tree mechanic to check the EBPV or sensor(s)? Brakes & bearings were good when I rotated tires last @ 180k in September and all the hubs on the trailer & truck felt cool to the touch while towing.

Pop the arm off the botom of the flap and wire it open.I did one of mine in the parking lot of a mexican joint in Hendersonville.

 

[1-tonmudder]

Also the hard metal line that goes from the EBPV sensor to the exhaust manifold is known to get stopped up from diesel soot.And IIRC poor fuel mileage was a system of that.

 

[thebrotherinlaw]

My 6.0 went from it’s regular 16 mpg’s to 8 when we were pulling a small camper across North Dakota. It was fine all the way there. We hit some strong headwinds and the mileage just dropped. It got a little better after I unhooked for a couple of days and it was like the computer reset or something. Really weird and it hasn’t done it since.

 

[Lurch830]

I noticed a significant decrease in mileage from Bucees. I have also consistently tracked a decrease from Sheetz

How significant? That will really mess up my NC travels when the one gets built in Mebane!

Pop the arm off the botom of the flap and wire it open.I did one of mine in the parking lot of a mexican joint in Hendersonville.

Thanks, I'll give that a try this weekend when I get back!

Also the hard metal line that goes from the EBPV sensor to the exhaust manifold is known to get stopped up from diesel soot.And IIRC poor fuel mileage was a system of that.

My 6.0 went from it’s regular 16 mpg’s to 8 when we were pulling a small camper across North Dakota. It was fine all the way there. We hit some strong headwinds and the mileage just dropped. It got a little better after I unhooked for a couple of days and it was like the computer reset or something. Really weird and it hasn’t done it since.

Keep the advice/ideas/suggestions coming!

 

[77GreenMachine]

How significant? That will really mess up my NC travels when the one gets built in Mebane!

2-3mpg

This was a consistent occurrence over a few years, with 5 different vehicles.

When I lived in Thomasville I had a pretty regular routine. Gas & Coffee at the Sheets by my house. I began to notice that when I did occasionally get gas elsewhere, I would get better mileage. So then I started only buying gas at the BP across the street from the Sheetz, and then would notice 2-3mpg better. It's very repeatable too, sometimes I get gas at Sheetz anyway out of convenience and still notice it, from any Sheetz. This was with a few different cars and my truck.

Same thing happened with Bucees in Alabama with diesel fuel. I love to visit Bucees, but we don't buy fuel there.

 

[Caver Dave]

2-3mpg

This was a consistent occurrence over a few years, with 5 different vehicles.

When I lived in Thomasville I had a pretty regular routine. Gas & Coffee at the Sheets by my house. I began to notice that when I did occasionally get gas elsewhere, I would get better mileage. So then I started only buying gas at the BP across the street from the Sheetz, and then would notice 2-3mpg better. It's very repeatable too, sometimes I get gas at Sheetz anyway out of convenience and still notice it, from any Sheetz. This was with a few different cars and my truck.

Same thing happened with Bucees in Alabama with diesel fuel. I love to visit Bucees, but we don't buy fuel there.

WAY off topic here, but interesting the 2 "cheapest" places for fuel and generally a haven for low(er)-income folks would be connected to lower MPGs...
Suspecting the 2-3mpg reduction associated, offsets the $0.xx less/gallon, making it a bad decision (financially) to fuel/shop there?

 

[Lurch830]

WAY off topic here, but interesting the 2 "cheapest" places for fuel and generally a haven for low(er)-income folks would be connected to lower MPGs...
Suspecting the 2-3mpg reduction associated, offsets the $0.xx less/gallon, making it a bad decision (financially) to fuel/shop there?

That coincidence made me raise my eyebrows too!

 

[Lurch830]

Well I dropped it off earlier today...we'll see how much damage this does to my wallet. Guy seems to be on the same thoughts as @77GreenMachine that I got unlucky enough to get a few bad tanks of fuel with low cetane in a row, but I'll update after I pay the bill in case it helps someone else in the future.

 

[Noel]

Well I dropped it off earlier today...we'll see how much damage this does to my wallet. Guy seems to be on the same thoughts as @77GreenMachine that I got unlucky enough to get a few bad tanks of fuel with low cetane in a row, but I'll update after I pay the bill in case it helps someone else in the future.

My 5.9 Cummins will randomly get horrible fuel mileage. I really need to start keeping track of where I buy fuel for this reason.

 

[shawn]

's very repeatable too, sometimes I get gas at Sheetz anyway out of convenience and still notice it, from any Sheetz. This was with a few different cars and my truck.

You're probably buying ethanol. That would cause a ~15% mileage reduction.

 

[Lurch830]

Diagnosis is in: probably lower cetane fuel which clogged the EBP tube & failed the EBP sensor...interwebz points go to @77GreenMachine & @1-tonmudder !
Tube cleaned, sensor replaced and I'll put some miles on it this weekend to verify that fixed it. The shop did ask if I used any fuel treatment and I've always used Lucas, but they recommended Stanadyne for improving cetane.