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True Gas Tank Capacity

Mdbtyhtr said:
Electric fuel pumps must be submerged to keep them from overheating. It is the same for your car or truck. I would not want to run too low as it will effect the longevity of the pupm. Another thing, lean = Heat, if you were to run low and the fuel pump can't deliver the proper fuel volume/pressure, your injectors won't fire properly and you could burn a piston.

Scott
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I was thinking along those lines. But now another question comes to mind. Does the bike stall after using 3.8 of the 4.8 available gallons or can you just drive through it & risk doing damage to the pump or pistons. It would have been nice if the manual said something like Tank Capacity 4.8 with a useable range between fill ups 3.8 Gallons. Even "Heck if we Know" would have been better than just saying 4.8 when it has a 20% error.

My guess it stalls at 3.8 of the 4.8 gallons. Can't imagine they would allow anyone to do damage trying to make it to a station. I mean who would not just keep driving till the engine quit?

Hoople
 
have you guys "SEEN" the fuel pump in the tank. The pump is rarely "submerged" because it stands straight up. there is also a "sock" on the end of the pump so don't think you would be sucking up any "debris"

I own a carbed bike with a fuel pump and I run it dry every time I hit reserve. been doing this for 10 years and 74,000 miles. The fuel pump still works, so I don't think running out of gas once is going to ruin or cause premature failure in the fuel pump. Now I know what they say, and I understand the way of thinking but........:dknow
 
I have a '03 UC with an electric fuel pump in the tank. I run about 165-175 miles between fill-ups and usually buy between 5.0 and 5.2 gals. At that point, my tank is pretty empty since I can have problems with the engine trying to die when I come to a stop (fuel runs away from the pick-up). Any cooling that the gas is doing for the pump it is doing as it is pumped, not because it is submerged in gas. As WindSpirit said, the pump is pretty much above the gas for about the last quarter tank. They do not run hot (or even very warm). That would be exceedingly dangerous in a fuel tank.

TQ
 
On my 08 Street Bob, the low fuel light comes on like clockwork at 160 +/- 5 miles. If I can hit a gas station right then, I will take 3.8 to 3.9 gallons. This is supposed to be a 4.8 gallon tank, so it looks to be very accurate to me. The gas gauge reads empty when the light comes on, just the way I think it should.
 
RetiredJake said:
On my 08 Street Bob, the low fuel light comes on like clockwork at 160 +/- 5 miles. If I can hit a gas station right then, I will take 3.8 to 3.9 gallons. This is supposed to be a 4.8 gallon tank, so it looks to be very accurate to me. The gas gauge reads empty when the light comes on, just the way I think it should.
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Yours is working just like I would have expected mine to work. That is, when the low fuel light comes on, you have appox 1 Gallon of gas left. That makes sense.

When my Low Fuel light comes on, I can ride another 30 miles (my average city MPG is 31) and at THAT point I can only put 3.84 Gallons in the tank.
Based on a 4.8 gallon tank, that does not make sense.

Thanks for the reply.
 
Hi

I have a 07 FXDL, no engine mods. Last summer I was out for a days ride with my son, mostly back country roads. We had gone about 180 miles, I was on reserve, and no gas stations in sight. Finally we came to small town and a gas station. I had 198 miles on the odometer, and after filling up it still only took about 4.3 gallons! Most fills after the low fuel lite comes on it takes about 3.3 gallons.

Don L
 
I posed that question to the mechanic at the dealership. I have an 09 Heritage Softail and he told me that when you fill the tank up you can never get it full to capacity. He said that the fuel pump is mounted inside the tank and that you only have about 4 usable gallons in the tank. I have never run out but with my gauge on empty and miles to go at less than 10 miles the most I can get in it is 3.8 gallons
 
I'll mention this one last time. The gauge and "idiot" light are not precision instruments. They are only designed to call the riders attention to the fact that he/she is getting low on fuel and should consider looking for a gas station. If you want to find out what your tank will hold and how much you can get to, keep riding it until you run out. Have a back up plan to add a known quantity back in the tank that is sufficient to get you to a station, and then fill it full to just overflowing. Add the two, and that is the amount of gasoline that you can use from your tank.

TQ
 
Thank you for all the replies. Great information but I actually believe the sensor for low fuel level and the reserve meter are actually precise gauges. Since the Results are repeatable to almost the last drop of fuel they can be considered precise instruments. The fact they can give you the same exact wrong value each and every time means they are PRECISE. They are just not calibrated.

If I was to fill up requiring a different amount each time, I would not have started the thread. That in itself would have told me the gauge and the entire fuel indication system HD uses was not precise.
The fact is, it is precise. It's just not calibrated.
 
Thanks Hobbit !
You answered my question.. I did not know when the Display shows --- it meant I COULD ride about 15 more miles. That explains my entire question. For me 15 miles is .5 Gallons (city milage with re-mapped VE tables). The other missing .5 gallon is probably the volume the pump & float takes up in the tank as mentioned in an earlier reply by Awall.

I was not trying to beat a dead horse. Yes, it's better to be "safe than sorry" & you should not run your tank dry etc etc... But since everything on the bike is built with such precision and detail, a 20% error on the electronic fuel gauge was a bit much. There are very few items in the world around you that you would accept with an accuracy of + or - 20%

The missing Gallon question has been answered.
 
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