Miriam Romero Posted May 9, 2022 Share Posted May 9, 2022 I’ve always used 99 gallons on the same route for 3 years. Last two weeks I’m using 17 extra gallons and can’t find any reason for it. Does anyone have any ideas of what could cause this? Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/ Share on other sites More sharing options...
Dirtymilkman Posted May 9, 2022 Share Posted May 9, 2022 Rebuild injectors and run the overhead. 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/#findComment-497132 Share on other sites More sharing options...
BOBWhite Posted May 9, 2022 Share Posted May 9, 2022 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 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/#findComment-497141 Share on other sites More sharing options...
Miriam Romero Posted May 9, 2022 Author Share Posted May 9, 2022 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 Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/#findComment-497175 Share on other sites More sharing options...
Popular Post JoeH Posted May 10, 2022 Popular Post Share Posted May 10, 2022 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. 1 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/#findComment-497214 Share on other sites More sharing options...
Popular Post fjh Posted May 10, 2022 Popular Post Share Posted May 10, 2022 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! 2 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/#findComment-497233 Share on other sites More sharing options...
Miriam Romero Posted May 12, 2022 Author Share Posted May 12, 2022 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! Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/#findComment-497414 Share on other sites More sharing options...
Miriam Romero Posted May 12, 2022 Author Share Posted May 12, 2022 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? Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/#findComment-497415 Share on other sites More sharing options...
Miriam Romero Posted May 12, 2022 Author Share Posted May 12, 2022 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 Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/#findComment-497416 Share on other sites More sharing options...
Popular Post fjh Posted May 12, 2022 Popular Post Share Posted May 12, 2022 13 hours ago, Miriam Romero said: 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? 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! 1 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/#findComment-497468 Share on other sites More sharing options...
Miriam Romero Posted May 12, 2022 Author Share Posted May 12, 2022 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. Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/#findComment-497472 Share on other sites More sharing options...
fjh Posted May 13, 2022 Share Posted May 13, 2022 (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 May 13, 2022 by fjh 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/#findComment-497526 Share on other sites More sharing options...
Miriam Romero Posted May 14, 2022 Author Share Posted May 14, 2022 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. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/#findComment-497651 Share on other sites More sharing options...
Mark T Posted May 14, 2022 Share Posted May 14, 2022 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. 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/#findComment-497657 Share on other sites More sharing options...
JoeH Posted May 15, 2022 Share Posted May 15, 2022 Leaky fuel tanks can cause bad fuel mileage.... 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69687-e7-fuel-mileage-dropping-for-seemingly-no-reason/#findComment-497690 Share on other sites More sharing options...
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