Itinerant Air-Cooled

I've noticed a weird pattern in the way my fuel gauge behaves and was wondering if anyone has a clue what might be happening.

I always get $10 worth of gas, this fills the tank to about halfway. For 4 or 5 batches I will get what appears to be 17 miles a gallon. Then after 4-5 $10 batches that normally fill the tank to halfway, a $10 batch will fill the tank to 3/4's and my mileage for this one tank will be much higher....Then the cycle repeats 4-5 batches that only fill it to halfway w/apparently low mileage, and then one that goes to 3/4 with great mileage. My bus really gets 20-21 MPG.
It's like the gauge is going to empty too fast for 4-5 batches and then realizes it's mistake on the 6th and gives me the "missing" gas back....

I'm guessing your float has a sticky spot in its travel and hangs up there unless you put a lot more gas in to force it past that point. I'm also guessing that over consecutive fill ups, the amount of total gas in your tank increases after each fill until there is finally enough gas to bump the float free again to read up around 3/4. Don't forget that as the price of gas fluctuates, so does the amount $10 buys!

How are you measuring mpg without filling the tank?

I'm gonna go out on a limb and suggest that you really can't calculate gas mileage the way you are doing it. These crap senders they are selling us only last about 2-3 years before they start going wonky on you. I go through at least 1 tank of gas a week, usually more.

I measured the mileage on a 6000 mile cross country trip....I usually note the mileage & quantity when I put gas in and see how how far I went before I need more.

The theory about the float having a sticky spot makes a lotta sense. I still run the original sending unit.

Does the needle on the gauge bounce ? MIne jumps around, then settles, then jumps....I left an access hole to get to the sender, just in case I had to get back in there...replaced the tank due to rust and black oozing tar like stuff in the tank - sat 10 years in Indiana....

Danny79 wrote:Does the needle on the gauge bounce ? MIne jumps around, then settles, then jumps....I left an access hole to get to the sender, just in case I had to get back in there...replaced the tank due to rust and black oozing tar like stuff in the tank - sat 10 years in Indiana....

Flicking jumpiness of the early guages can be attributed to the wiring much of the time, the wiring at the gauge head. These earlier units use a vibrator that needs clean secure connections.
Colin