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E7 Fuel mileage dropping for seemingly no reason


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How many miles is the route? Check and see if there's much black smoke, you could be over fueling but I doubt that would make a 17 gallon difference. Park it in a parking lot or find some cement to see if you have any leaks. Good luck 

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12 hours ago, Dirtymilkman said:

Rebuild injectors and run the overhead. 

11 hours ago, BOBWhite said:

How many miles is the route? Check and see if there's much black smoke, you could be over fueling but I doubt that would make a 17 gallon difference. Park it in a parking lot or find some cement to see if you have any leaks. Good luck 

546 miles

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On 5/9/2022 at 8:29 PM, JoeH said:

How's your Pyrometer reading? How about your Boost gauge? We just replaced the charge air cooler on our '95 E7-350 and it's a night and day difference. Picked up 10 psi of boost and dropped 2-300 degrees on the pyro.  Had a cracked charge air cooler.

I’ll have hay hubs (mechanic) check that  we just put a new  charge air cooler!

 

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Now my 2012 is regenning every 30 minutes!

geez! Will it ever end???

the only code for this one was the sensor. We bought the sensor today $1000 at Mack.

I just test drove it and it’s still needed a regen before I got back. It’s regenning now as I type.

any ideas on this one?

 

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On 5/10/2022 at 8:14 AM, fjh said:

Yup model of truck would help ! CH or RD ? check the tube that goes to the compressor inlet  from the manifold

hose there quite often gets a hole in it! Any kind of boost leak! all will effect mileage! instantly!

Ch e7 460

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16 minutes ago, fjh said:

No it doesn't! Sensors are just as good as the info they get ! You can Guess and change parts All you want with these you need to have the program on a computer screen and A fare bit of knowledge and mostly experience of  the system to go right to the problem to fix AND a whole lot of luck! Go to a dealer and have the codes read maybe they can fix or send u in the right direction ! You can have anything from a failed  7th injector ,or EGR cooler to a pluged Venturi tube  causing this!

7th injector replaced. Venturi tube is clean.

My husband has been a Mack mechanic for 30+ years. This DPF system is fairly new to him but his partner taught mechanic classes for Mack for years and is very knowledgeable in this. We need lots of luck at this point. 
one guy said it could be stuck open or partially open egr valve. Another points to turbo. The turbo sounds exactly as it always has but I’m just the driver/wife of mechanic. I should add…frustrated wife/driver. This is overwhelming. 3 expert Mack mechanics and still broke down. 
thank you for your input! Husband says he’s done everything that you’ve said.

the mechanic with the laptop has the last updated laptop tools and said the regen is burning it all off correctly. He said it’s suppose to take 30 minutes and it does and the temps are spot on.

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Posted (edited)

Well if its burning  it off and then creating more in short order  then something is creating soot,  Injectors, turbo ,  boost leak stuck egr! in my opinion like I said This is where the experience  and luck part comes in! 

These can be horribly frustrating for everyone to own to work on and if you don't run across the right realworld experienced  guy at any given shop to get your repair diagnosed and repaired it gets expensive AND Some times it comes down to guessing  AND Parts chucking! it only gets worse as the truck ages!  Remember Nobody knows everything or seen it all even thou ,they would like to think so! All we can do is tell ya what we seen and our experiences here ! I am not a guru on these some one might chime in with some  thing that strikes them as odd ! Good luck with this you guys keep posting as you run thru the fix Most of all post your FIX so others may benefit by your experience! 

 

Edited by fjh
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We have decided to buy a laptop with the Mack software and all the cables needed. We are tired of guessing and paying $200 to $400 everytime someone comes to help us using their computer. It’s expensive but we can work on many trucks and be the one charging for diagnosing troubles. 
Since my husband is an “old school” Mack mechanic, it’s past time for us to get into the new century of computerized trucks. 
Now, let’s hope my minimum computer skills will help us learn. The mechanic hooking us up with what we need says he can teach me basics and the computer will do the rest. 
Thanks for your input! I really appreciate you and all the others replies and I will update our progress. 

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Not to offend anyone, but poor mileage for no reason easily detected usually turns out to be a leak somewhere in the intake.  Maybe it's time to recheck all the simple things again ?  Easy to get frustrated and miss something some times......we've all done it.

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