New Injectors, Poor Fuel Mileage

[anderson.m.steven]

I'm at a loss for what to check/test next to figure out why my MPG has dipped after replacing injectors. Thoughts/comments/insight would be greatly appreciated!
Below is a brief timeline of what has gone on ...

January 2014, bought the truck used with 97,000 on the clock and would get roughly 15-17 MPG (hand calculated) with a mix of highway/city driving.

September 2014, #4 injector line broke and sprayed fuel everywhere ... that tank ended up being 14.5 MPG. Replaced the line and averages were back up to 16/17 MPG.

November 2014, I took the truck to a shop to have the injectors cleaned and tested, two were replaced with reman'd injectors and was told that a compression test showed roughly 250PSI across all cylinders (low?), but the truck ran great otherwise. MPG had now dropped to 13/15 MPG

January 2015, Started experiencing idling misfires during cold warmups. MPG is now 13/14.

April 2015, Installed full set of new Bosch injectors & feed tubes, and adjusted the valves.

Present, MPG has slowly improved, but is still right around 14/15 MPG ... nowhere near the 15/17 it used to get before that first injector swap.

Notes
Oil level stays constant between changes.
Stanadyne Blue every 2nd/3rd tank doesn't seem to change MPG
No apparent fuel leaks anywhere.


What am I missing?

 

[TRAMPLINEMAN]

My '06 did the same thing. I changed all 6 with stock Bosch. After the install, the truck ran great but the mileage was slightly less. Why? No idea.

 

[cerberusiam]

Compression should be close to 300 on a warm engine, probably lower if it is cold. Real measure is if it is consistent on all cylinders.

Where did you source the injectors? Can you positively verify they were NEW virgin injectors from a reputable source?

Has anything changed or been changed? ECU flashes? Tires, etc?

 

[Mathes308]

Could it be that your worry combined with having new injectors is causing more use of your right foot than normal.
I know when I'm concerned or listening for bad sounds I tend to burn more fuel trying to see or feel for abnormalities.

1mpg is easy to sway with unnoticed throttle.

 

[anderson.m.steven]

The shop probably did the compression test on a cold engine, so that might explain the 'low' readings. Leak-down test showed very little loss from what I was told. Since then, I've read that a blow-by test is more accurate in gauging the health of these motors anyways, so I will do that soon.

Sourced the injectors & tubes from what I thought to be a reputable source (AccurateDiesel), and I'm not exactly sure how I could tell a reman'd injector from a new one side-by-side, but the packaging and everything sure seemed legitimate.

There definitely have been changes since the injectors were installed, but none seem to affect the MPG:

BFGoodrich All-Terrain KO2 275/70R17 (Originals were BFGoodrich Rugged Trail 265/70R17)
New dampers all around
Couple of ECU flashes. One before mileage dropped and one after, neither or which seemed to affect MPG.


Actually, it might be easier to just link to my maintenance logs to show MPG trends and everything else:

https://docs.google.com/spreadsheets/d/1WC5zVpqfAVa_SRrpEtHuU_oHoZsgIu_tPD_EA_4Oro8/edit?usp=sharing 2014
https://docs.google.com/spreadsheets/d/1_eV116nqAk5L1e46gHo7mhEQhLtnpgAbxqCoAOzujjE/edit?usp=sharing 2015

 

[anderson.m.steven]

Could it be that your worry combined with having new injectors is causing more use of your right foot than normal.
I know when I'm concerned or listening for bad sounds I tend to burn more fuel trying to see or feel for abnormalities.

1mpg is easy to sway with unnoticed throttle.

Good question, but actually I used to drive this thing like a racecar from day-1. Since the injectors, I've actually tamed it wayyy down and actually tried to see how far I could push the mileage. It has helped a little, but even when I have a long highway trip and just set the cruise I can't seem to break 15MPG (see previous post for MPG trends).

 

[cerberusiam]

Did you adjust pinion factor for the taller tire?

 

[anderson.m.steven]

Did you adjust pinion factor for the taller tire?

I had thought about doing that, but have not yet because the MPG was already in the 14's after the new injectors, and before the new tires went on.

I would gladly get it adjusted if anyone knows of a good place in the Maryland/NOVA area.

 

[cerberusiam]

Might not be able to adjust it for the size tire you have. The dealer had minimal adjustments they were willing to do. Your best option is buying a Smarty to tune it and adjust pinion factor. That will probably bring your mileage back somewhat also. The differences in the tires you are probably back into your 15-17 mpg range now if you measured miles correctly. You are coming up short with the taller tire for total miles.

 

[AH64ID]

Couple of things.

New tires will always get lower Mileage than used ones.

Your odometer isn't accurate with the new tires so your actually getting better mileage than you think.

As injectors wear they get better mileage, so new injectors won't achieve the same mileage as old ones. It isn't uncommon for people to go for 100-200K miles on original injectors and replace them with new OEM ones and feel like they lost power and mileage.

I would give it some miles and fix your odometer.

 

[cerberusiam]

What numbers were on the packaging? Did they come in a Bosch or Cummins box? How much did you pay for them?

They are selling supposed NEW injectors for what EVERY Bosch dealer is selling remans for, and, well under what every reputable dealer sells new OEM for. It just seems suspicious, it seems you are not the only one to observe this, and if you figure out a way other than a Bosch engineer to tell if they are new or reman everyone would like to know.

If you had bad injectors before, out of the box good new injectors should have increased the mileage immediately. I cannot buy into the injector needing to break in, have not had that experience. Always, new increased mileage sometimes more than the best before.

Get the speedo back accurate and test again for mpg. As long as it gets back to where you think it should be and you don't have issues starting, you probably have the best solution for the price.

 

[anderson.m.steven]

New tires will always get lower Mileage than used ones.

Your odometer isn't accurate with the new tires so your actually getting better mileage than you think.

As injectors wear they get better mileage, so new injectors won't achieve the same mileage as old ones. It isn't uncommon for people to go for 100-200K miles on original injectors and replace them with new OEM ones and feel like they lost power and mileage.

I would give it some miles and fix your odometer.

I'll definitely keep watching the trend to see if continues to increase, and definitely agree that worn tires should have less rolling resistance than new ones. As for fixing the odometer (which I should get done, but stealership wants $150 to hook it up), hand calculations show that I should only be experiencing an error of -1.7% (Revs/Mile) with the taller tire. That doesn't quite make up for the -8.8% difference in average MPG that I'm seeing.

 

[anderson.m.steven]

What numbers were on the packaging? Did they come in a Bosch or Cummins box? How much did you pay for them?

They are selling supposed NEW injectors for what EVERY Bosch dealer is selling remans for, and, well under what every reputable dealer sells new OEM for. It just seems suspicious, it seems you are not the only one to observe this, and if you figure out a way other than a Bosch engineer to tell if they are new or reman everyone would like to know.

If you had bad injectors before, out of the box good new injectors should have increased the mileage immediately. I cannot buy into the injector needing to break in, have not had that experience. Always, new increased mileage sometimes more than the best before.

Get the speedo back accurate and test again for mpg. As long as it gets back to where you think it should be and you don't have issues starting, you probably have the best solution for the price.

Don't remember numbers on the packaging, but I might have taken pictures (I'll look for them) and believe it was Bosch packaging. Price ...$330 each (plus refundable core).

As for performance, I want to get it on a dyno to see if I'm close to stock power. It also fires right up and seems to idle just fine.

I'm assuming aside from pulling the injectors and getting them tested/replaced, there's not much I can troubleshoot?

 

[cerberusiam]

hand calculations show that I should only be experiencing an error of -1.7% (Revs/Mile) with the taller tire. That doesn't quite make up for the -8.8% difference in average MPG that I'm seeing.

Unfortunately the differences are not linear, it is more like 5-6% in miles. That does add up, not to all you lost in mpg but more than the tire size difference.

I'm assuming aside from pulling the injectors and getting them tested/replaced, there's not much I can troubleshoot?

It is highly doubtful you could find anything by having them tested. The quality of the testing is suspect and open to interpretation.

The mileage is drastically effected by ambient temps and conditions, summer is frequently not a good time to check mpg.

Considering what the dealers want and how hit or miss it is, and, the fact a Smarty will tune it for better efficiency, you are much better off going that route. Then you can adjust the speedo closer than stock, they are all off to a certain extent.

 

[anderson.m.steven]

Unfortunately the differences are not linear, it is more like 5-6% in miles. That does add up, not to all you lost in mpg but more than the tire size difference.

The mileage is drastically effected by ambient temps and conditions, summer is frequently not a good time to check mpg.

Considering what the dealers want and how hit or miss it is, and, the fact a Smarty will tune it for better efficiency, you are much better off going that route. Then you can adjust the speedo closer than stock, they are all off to a certain extent.

And I've always thought winter was a poor time to check MPG due to the winter blend ... :-|

I eventually wanted to tune with EFILive, but that doesn't have the capability to reprogram the pinion factor. Would I have to get a 'stock' tune with a smarty or something similar first, then do an EFILive tune?

*NOTE* I've fixed the permissions to the 2015 google doc link in the 1st post.