Author Topic: Cummins/Cat or Mercedes  (Read 4127 times)

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Offline Powerstroke2000

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Cummins/Cat or Mercedes
« on: August 03, 2016, 05:37:17 PM »
My wife and I are the point of trying to acquire our first Class A motorhome, and as I'm sure as your all aware, there are a multitude of things that goes through one's mind, and that is to get one that will give us the 'least' amount of trouble!   Notice a nice Tiffin unit today, and found it has a Mercedes diesel engine, and most tend to be Cummins the I've seen, so I thought it best to ask the experts!
I'm currently going to through a 'fuel' related issue on my '09 F450 Ford pickup, of which will be in the $7,000. to $10,000. in repairs...so I'd definitely prefer to go through the checks and balances of getting a unit that isn't going to be troublesome (if that's possible).   I know, maintenance is paramount...yet even knowing I went over and above on my own maintenance on my pickup...and it still ends up biting me you know where!!   I did hear that there has been an issue with one Cummins engine (I thought it was told to be a 2005-2006 engine) but other than that, I haven't heard much on the diesel engines that push these motorhomes all over the country.   
At any rate, please feel free to 'educate' me, as I'm all ears.    Thanks so much!

Offline Brett Wolfe

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Re: Cummins/Cat or Mercedes
« Reply #1 on: August 03, 2016, 06:15:58 PM »
Welcome to the Diesel RV Club.

No problems with the MB engine.  My only reservation is that they were used in very few motorhomes, so not many are familiar with servicing them.

I guess my opinion would be to not make a coach decision based on engine (all three are good), as the primary criteria.

Offline Five

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Re: Cummins/Cat or Mercedes
« Reply #2 on: September 03, 2016, 05:18:48 PM »
MB is normally in the very small Class B MHs.  The Cummins/Cat engines are both fine.  When I was looking for my first MH, I leaned toward Cummins just because there are more in the MH industry, plus Cat no longer makes new MH engines.
American Coach Allegiance
400 HP ISL, 3,000MH Allison
Spartan Chassis

Offline Brett Wolfe

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Re: Cummins/Cat or Mercedes
« Reply #3 on: September 03, 2016, 06:03:52 PM »
Actually MB makes diesel engines in virtually all sizes.

Just Google "Mercedes 7.2 liter diesel 926".

This is the one found in Class A DP's.

Offline vrodboy

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Re: Cummins/Cat or Mercedes
« Reply #4 on: September 06, 2016, 06:38:22 AM »
We have the CAT C7 in our 2005 Fleetwood Discovery. Engine runs fine, but is hard to start! Service manager at Sacramento Fleetwood dealer says this is common for this engine.

So, it usually takes 3 separate cranks to start the C7 when cold. Once started, it will start immediately for the day.

Cheers All,

Ed and Deb

Offline Five

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Re: Cummins/Cat or Mercedes
« Reply #5 on: February 25, 2017, 03:44:51 PM »
I realize this is an old thread.  However, I wondered if the last poster can preheat his engine...that will take care of the "cold engine" problem.  In fact my Cummins ISL said to turn on the preheat if the temp would be 40 or lower.
American Coach Allegiance
400 HP ISL, 3,000MH Allison
Spartan Chassis

Offline Doug Mihoky

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Re: Cummins/Cat or Mercedes
« Reply #6 on: February 26, 2017, 09:29:31 AM »
I have the Cat C7 too, and it has always  taken a few cranks of the engine to start.  The preheat is a big help on cold mornings for sure...  I think it's the nature of the beast, this C7 engine...
Doug Mihoky
C7, 2005 Tropi Cal LX

Offline ziggyh

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Re: Cummins/Cat or Mercedes
« Reply #7 on: February 26, 2017, 07:24:07 PM »
C7-C9 and other cat engines with HEUI injection systems do require a little longer cranking time and preheat does help.  There are a few issues with these systems that add to the long cranking time, the most common is the fuel check valve\pressure regulator in the return side of the fuel system at the back of the head allowing the fuel to leak down when sitting and fuel line suction side air leaks.  Low cranking fuel pressure event codes are usually accompanied with the condition.  If the engine has a hand primer, priming the system before starting will help start the engine quicker.
ZiggyH

2007 Revolution LE
C9