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Old 03-07-2013, 08:13 PM   #1
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Mpg gauge never gets over 5 mpg

The last time I drove my 86 itasca the mpg gauge would read about 20 mpg at idle. Now it reads no better than 5 mpg. Can anyone help?
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Old 03-07-2013, 08:27 PM   #2
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What do you get with a fill up and actual miles traveled?

Ken
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Old 03-07-2013, 08:36 PM   #3
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Nuthin more accurate than a calculator using actual numbers. I have not looked at the computer (guess-o-meter) numbers. At best, would be only an estimate.
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Old 03-07-2013, 08:38 PM   #4
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Also it seems to be idling rough. Recently replaced the fuel filter and discovered trace amounts of rust. Would an obstruction in the fuel line cause this? I recently posted that my fuel gauge was reading incorrectly. I know am beginning to suspect something's wrong and its drinking gas. I found the vacuum line where the gauge is connected and it seems to be free of obstruction. However when I unplug the top tube ( it goes into a three way splitter) the engine dies. Unplugging the mpg gauge seems to have no effect.
Getting tired of this thing. My sell it soon as we have been unable to go anywhere in it. It just sits in the driveway and consumes money.
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Old 03-07-2013, 08:41 PM   #5
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What do you get with a fill up and actual miles traveled?

Ken
Well I haven't been back to the pumps since I filled up (30 gal) drove it 34 miles and it reads half a tank. So about 2.5 mpg. If the gauge is correct.
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Old 03-07-2013, 08:44 PM   #6
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I haven't been back to the pumps since I filled up(30gal). Drove it 34 miles and the fuel gauge reads 1/2 full or 1/2 empty depending on your psychological bend. So what's that ? Bought 2.5 mpg.
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Old 03-08-2013, 09:38 AM   #7
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You should probably go back to the gas pumps and fill up again to make sure the gauge is working correctly. When you're done, take the # of gallons you need to add to re-fill it and divide that into the 34 miles and that's your mpg.

Other factors can be at play as well, such as are you using the generator at all? If so, it's connected into the main fuel tank as well as the engine, so you won't be getting a acurate mpg # if that's the case. Have you been letting it sit and idle a lot since you've gotten it? 5mpg on a 454 that needs maintenance isn't unheard of.
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Old 03-08-2013, 09:57 AM   #8
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hi if this is a vac gauge style it means your mtr needs a tune / carb issue or a vac line has gone bad
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Old 03-08-2013, 12:33 PM   #9
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this is just me, but if i thought my gauge was off..that much. I would fill up, bring a gas can full with me..and see how many miles (locally) i could go till it got down to nothing ( run it almost out of gas)...then write milage down, and divide. as then you would know rather or not you could trust the gauge..2.5 mpg seems unreal...to me..
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Old 03-11-2013, 02:58 PM   #10
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OK. For anyone who is interested I found the problem. And yes LaZy507 i did the math as you suggested. First off the gas mileage was around the 11 to 12 MPG range. The culprit was a nearly broken vacuum hose. It was cracked and Kinda falling off the vacuum canister. Thanks to all tha contributed! This forum is awsome!
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Old 03-11-2013, 03:49 PM   #11
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awesome glad you figured out the problem..11 is way better than 2..haha glad it wasnt nothing too serious.
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Old 03-11-2013, 04:45 PM   #12
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Also check the mechanical advance weights in the distributor. If they don't move freely it can mess around with MPG.
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Old 03-12-2013, 05:16 PM   #13
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Quote:
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The last time I drove my 86 itasca the mpg gauge would read about 20 mpg at idle. Now it reads no better than 5 mpg. Can anyone help?
Most of the mechanical pre-EFI MPG gauges that I know of are simply vacuum gauges... Likely you've got a vac leak or the line is bad.
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