Fuel gauge is the new Tach these days...

[1980Galaxy]

So just as the topic says: my fuel gauge fluxuates with the rpm. i just installed new gauges and now this is happening. the old one really didnt work right either but it seemed to work better than this. the gauge reads about 1/4 with idling but the tank was topped off. could this be a sender problem? any thoughts would be appreciated.

P.S. i did a search about this and i realize that fuel gauges arent accurate with the swing arm senders and all that, but i should at least have a general idea of how much fuel is in the tank and it should work OK when im just sitting in the water idling.

 

[Silvertip]

Re: Fuel gauge is the new Tach these days...

Everyone seems to think swing arm fuel senders aren't accurate when indeed thay are fairly accurate if you understand how they work and what they are telling you. Most people equate 1/2 full on the gauge as 1/2 of the capacity of the tank. That is simply not true and can only be true if the tank has a uniform shape from top to bottom and end to end. Think of a the typical cone shaped paper cup. When full the cup holds (for example 8 ounces of liquid). But when the liquid level is half way down there much less than 4 ounces left in the cup since the bottom half has much less volume than the top half. Therefore 1/2 on the gauge is rarely 1/2 the volume but is actually one half the "level" of the fuel. These two terms are not the same. So as fuel level drops the fuel can slosh around and make the needle bounce. It doesn't mean it's inaccurate. Now to your question -- You very likely have a wiring problem since the gauge does not read correctly and it varies with engine rpm. The gauge requires 12 volts for operation. If your electrical system voltage is varying wildly the gauge will respond in like fashion. It's obviously not the gauge. Disconnect the send wire either at the gauge or at the sender measure the sender resistance to ground. If you know how much fuel is in the tank you can tell if the sender is bad or not without removing it from the tank. A good sender measures 30 - 240 ohms across its range. If you have 1/2 tank of fuel the sender should measure about 109 ohms. For less or more fuel you can do the math. if the sender is ok then you need to look at the charging system and grounds.

 

[1980Galaxy]

Re: Fuel gauge is the new Tach these days...

haha... i kno, i read all your posts about that cone shaped gas tank.

i have a square gas tank tho so a swing arm should work well for me cept for the sloshing around but i dont mind that. im just concerned about the sitting still and having the needle still bounce all over the place and read totally inaccurate.

thanks for the advice, i will try that next chance i get.