Abysmal mileage

[azpete]

yeah, hook it to a computer with the right testing software

i has a miss in my caterpillar engine. finally it wouldnt pull the hills like it should.

i took it to johns diesel service in tucumcari nm. small shop. but super good. they found one injector partially clogged, and one with a dead magnetic coil. as well as a bad atmospheric sensor.

i watched as the tech ran thru the computer test, and saw the results for myself.
i have always run seafoam in my fuel, but the injector was still clogged. we removed the nozzle and checked the blockage to be sure it was really clogged.

anyway, as long as the engine was torn apart, i have them replace all six injectors, and replaced both the fuel filters .i dont want to chance this happening while on a back road in montana, or nowhere usa.

now instead of 4.6 it gets 8.5. worth the investment.

[dadej]

Originally Posted by Pdvitalis

I do have a heavy foot and drive 5 to 10 over the speed limit but it always gets 4.5 no matter what the conditions, long trips, short trips, stop and go or highway.

No way! Speed limit 75 and you are driving 85???? I will bet you if you slow to 55 you will get better mileage. As speed increases mileage goes down no matter if it is a Honda or a truck.

[Pdvitalis]

Originally Posted by dadej

No way! Speed limit 75 and you are driving 85???? I will bet you if you slow to 55 you will get better mileage. As speed increases mileage goes down no matter if it is a Honda or a truck.

LOL. I did a trip across SD where the speed limit was 80. I couldn't get much over that . As for the 55, no can do. I literally can't go under the speed limit. I see semis going 3 under every day clogging up traffic for miles sometimes. I am generally driving at the speed limit now and not always accelerating under full throttle... I'll see how that goes.

[Sweetbriar]

Any one in the area where you park the coach own a diesel vehicle? Maybe a locking fuel cap will improve mileage?

[Pdvitalis]

Originally Posted by Dav L

2002 43' 500hp ism = 7.5mpg driving the speed limit on most highways.
something is wrong if you are below 7mpg.
First: Exactly how are you calculating mileage?

I log each fill up; the number of gallons and the odometer reading. I try to top it up each time. I use a spreadsheet to divide miles driven by gallons used. I made a mistake on my previous posts. My mileage is 5.4 not 4.5. Still awfully low though. Thank you all for your suggestions. I'm writing them down now and will take them along with the coach to the Cummins service center when it gets closer to winter.

[CountryB]

I think you have a leaking injector or two (not clogged). Cummins can run a cylinder power balance test and an Injector test to confirm. Also be sure to smell your oil for any signs of diesel fuel getting in the crankcase. You should be able to pull the dipstick and take a sniff there. Oil diluted with diesel fuel is bad for the engine.

http://www.enginebuildermag.com/2012...ill-be-tricky/

[gkonney]

Just MHO on this subject we have a 2018 Newmar with a 450 Cummins which just turned 6K miles. We have not really been impressed with the mileage coming from a 5th Wheel and a 6.7 Ford. We just witnessed 8.1 mpg down in South Florida this week and I guess that is what we will be living with.
We live in Charlotte, NC and I will begin looking for a Cummins specialist there when we return. I'm hoping that with all of those Dodge Trucks out there tuned up someone must have a handle on how to tune these 6 cylinder diesel pusher for maximum performance...and economy. I'm thinking the factory just cranks them out even if then are all choked up??

[Midwestman]

Originally Posted by twinboat

Getting A diesel to just run rich is a challenge.

Sure a few injectors or a badly clogged air filter will contribute to a rich condition, along with a rough running engine, but since diesels don't have throttles and are open to all the air they can pump in, the only thing that controls engine RPM is fuel.

Inject more fuel and the engine goes faster. That's the basics of them.

In a good running diesel, only lugging it will cause black smoke, and since electronic fuel control, that's even been eliminated. They are programmed to not over fuel.

The OP should have a shop connect it up to a computer and get a performance readout. Then go from there.

Glad you said this - you can't run a diesel rich like you can a gas engine - unless your air filter is clogged.

We have a 38' Dutch Star with 330HP cummins. Get between 7-8mpg with it - I'm very happy with that

[JFXG]

Originally Posted by Pdvitalis

I log each fill up; the number of gallons and the odometer reading. I try to top it up each time. I use a spreadsheet to divide miles driven by gallons used. I made a mistake on my previous posts. My mileage is 5.4 not 4.5. Still awfully low though.....

Do you run your generator a lot, including while traveling? If so, does your spreadsheet extract the gen fuel and leave you a net fuel to engine?
What chassis are you on? If Freightliner, consider using the Freightliner service center in Gaffney, SC. They do excellent work there.
My ‘02 DutchStar has averaged about 7.5mpg @ ~65mph while towing for the past 6.5 years. It is 40 ft with a 330hp Cat, and with toad I gross out at ~35K Lbs. If you are similarly set up— if you’re moving about 100 Lbs/hp— then you should enjoy a somewhat similar fuel economy.

[dexters]

Originally Posted by MSHappyCampers

Hi ! Welcome to IRV2! We're sure glad you joined the gang!

I can't offer suggestions about the low mileage.

Good luck, happy trails, and God bless!

+1.