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How to verify engine fan operation

Yahoo Message Number: 16225
Hello folks

I am getting really bad fuel mileage (6-7 MPG) and am looking for causes. In my research, I've read where one of the possible causes could be that the engine/radiator fan is running on high mode continuously. My transmission and engine temperatures are running on the low side of normal, so I was wondering about the fan operation. If the fan was running on high all the time, then the hydraulic pump on the engine would be running more than it needs to (since it runs the fan) and placing an unnecessary load on the engine. Anyone know how to verify that the fan is operating properly?

Larry, Debbie, Tiki and Tomi (Pugs) USAF Retired

2003 Allure #30856

18,000 miles on odometer

Re: How to verify engine fan operation

Reply #1 –
Yahoo Message Number: 16226
On my previous coach (Monaco Exec), the same thing happened and because the fans were running all the time, the bushings in the fan motors wore out and would spray hydraulic fluid all over everything, including my toad (which would drip hydraulic at the end of the run). The way I found out that the fans were running was to open the engine cover and start the engine (cold) and see if the fans are running. They should not run when the engine is cold, in fact I was told that they shouldn't go on until your engine temp is over 180. However the fix, which was $3000, didn't improve the fuel mileage but it did improve my hydraulic miles per gallon.
My 97 Allure, which is new to me, just made 8.5 mpg in my first road test of 750 miles. It has the Cummins 325hp in it and my toad is a Ford Explorer. I did keep it at about 60mph most of the time.
Jim Howell Allure #30114

Re: How to verify engine fan operation

Reply #2 –
Yahoo Message Number: 16229
Larry, one way to tell if the fan is always running the same speed is to turn your dash air on and off. I believe the fan automatically goes to full speed when the dash air is on.
Also, your poor fuel efficiency can depend on your speed. I have a coach very near to yours (30811) with the 370hp Cummins and fairly consistently get 7.5 to 8.0 mpg when driving 60-62mph. Anything faster and the efficiency goes down pretty quickly.
Also, are you accounting for usage by the generator and the Hurricane? I calculate 3.0gph on the Hurricane and 4.0gph for the Onan, using actual meter hours.

I hope I have been of some help.

Walt Rothermel
03Allure30811

Re: How to verify engine fan operation

Reply #3 –
Yahoo Message Number: 16230
Hi Walt,

Something must be seriously wrong with your gen, my fuel consumption has always been very minimal. Onan states for an 8.0 KW at full load should be 1.02 per hour and 1/2 load .49 per hour. Same with my hyro- hot, fuel consumption is next to nothing.

Just curious...
Tom

04 Allure 30979

Re: How to verify engine fan operation

Reply #4 –
Yahoo Message Number: 16231
Larry,

Forgot to mention a very simple way to verify that you fan is running at high vs idle speed. Disconnect the 6 wire connector to the fan controller, the fan will then go to full speed, and you will know it immediately because of the difference in speed. If you don't see any difference when you disconnect the 6 wire connector then it is already running at high speed. The fact that your engine temps are low is another good indicator, before mine was fixed my engine temp was always just under 180, now it is well over 180. The air sensor was bad on mine and has failed at least twice due to it's location...mounted in the bottom side of the air duct thus causing it to hold a puddle of condensation all the time which hastens it failure.
Ray

Quote from: Larry Feather
>

Hello folks

I am getting really bad fuel mileage (6-7 MPG) and am looking for > causes. In my research, I've read where one of the possible

causes

Quote
could be that the engine/radiator fan is running on high mode > continuously. My transmission and engine temperatures are running

on

Quote
the low side of normal, so I was wondering about the fan
operation. If

Quote
the fan was running on high all the time, then the hydraulic pump

on

Quote
the engine would be running more than it needs to (since it runs

the

Quote
fan) and placing an unnecessary load on the engine. Anyone know

how to

Re: How to verify engine fan operation

Reply #5 –
Yahoo Message Number: 16233
Thanks Walt and Ray for the feed back. This gives me a starting point. Walt, I thin you meant .3 and .4 gal per hour didn't you? Thanks again.

Larry 30856

Re: How to verify engine fan operation

Reply #7 –
Yahoo Message Number: 16235
Tom, pls see my response re usage. I slipped a decimal. Even at that you are showing much lower consumption than I have ever heard.

Walt

Re: How to verify engine fan operation

Reply #9 –
Yahoo Message Number: 16250
From: "Larry Feather" ldfeather@...>

Quote
I am getting really bad fuel mileage (6-7 MPG) (snip)
What's your cruising speed ... and have you compared odometer reading with interstate mile markers to determine distance correction factor? You might be getting better mileage than you think .

Dick (& Geri) Campagna (in Brunswick, GA) '98 36' Intrigue #10571
Mfd: 11/97

Re: How to verify engine fan operation

Reply #10 –
Yahoo Message Number: 16256
Dick

My cruising speed is 65. Interesting thought on checking the mileage markers. Thanks.

Larry #30856

Quote from: Dick Campagna
> From: "Larry Feather"

> I am getting really bad fuel mileage (6-7 MPG) (snip) > > What's your cruising speed ... and have you compared odometer reading

with

Quote
interstate mile markers to determine distance correction factor? You

might
 

Re: How to verify engine fan operation

Reply #11 –
Yahoo Message Number: 16259
Larry probably has the fan running all the time. When my cooling fan was running at high speed, my mileage was around 6.5, since getting that problem fixed the mpg is around 8....I also had injectors replaced at the same time but Cummins engineers told me they felt the fan load was causing the mileage to be low since it consumes about 30hp when running at full speed.
Ray

Quote from: Dick Campagna
> From: "Larry Feather"

> I am getting really bad fuel mileage (6-7 MPG) (snip) >

What's your cruising speed ... and have you compared odometer

reading with

Quote
interstate mile markers to determine distance correction factor?

You might