94 Accord - Fuel gauge suddenly reads below empty, but light not on

In the space of driving about 10 miles, my fuel gauge on my 94
Accord went from about 1/8 full to below empty. However, the
low-fuel warning light next to the gauge has not turned on, and I
know from the trip odometer that there's plenty of gas in the tank.

Are the gauge and the warning light driven by the same sending unit
circuit, or are they separate? It seems to me if they are the same,
than there's a problem with the gauge itself in the instrument
panel, but if they're different, then the problem may be with the
sending unit that drives the gauge, or perhaps somewhere in between.

Can someone describe, or point me to a wiring diagram of, the
relevant circuits? Is the sending unit just a variable resistor
between +12VDC and ground? What about the gauge - what is it
measuring?

Also, is there access to the sending unit without having to drop the
tank? Is replacement something a normal but very handy human can
do?

 

you don't know that from the odometer at all. fuel gauges don't have a
linear sweep - it accelerates as the tank empties to encourage you to
re-fill. go to the gas station, fill the tank to the top and note the
quantity of gas the tank takes. then look in the owner manual for the
tank capacity and compare that to what you just filled. that will give
you a read on whether the gauge is working.

 

jim beam says...

Well, I've been driving the car for 14 years, and have a
pretty good idea how many miles I get per tank. I reset the
trip odometer at each refill, and usually base the refill
point on the miles driven unless it's an unusual
circumstance such as all-highway driving.

I did finally get to the refill point per the odometer, and
filled the tank. It took the usual amont of gas, as I
expected. Now the fuel gauge shows only 3/4 full instead
of full as it usually does. So, something is wrong
somewhere.

 

none of which you stated in your original post. and it /still/ doesn't
mean that you can rely on your odometer - dropped coolant level will
kill gas mileage for instance.

so check the sender unit.

 

If you gauge is not going to full when you fill up your tank then you
have a bad fuel sending unit. I too had the same problem on my 95
Accord and the light never worked either. Once I replaced my fuel
sending unit, both issues went away and the light now works.

You could also have a burned out light but regardless if your meter
isn't reading to Full any longer, that is an indication that the FSU
is bad.

 

says...

Ok, so let me ask again if anyone remembers for this series
of Accords where the access to the sending unit is. I don't
see anything in the trunk. Is it under the rear seat? If
so, how do you get the seat out?

 

You have to remove the two rear seatbacks, then the spare tire cover, then
the mid-floor cover. There's an access panel under that.

Removing the rear seatbacks is a Chinese puzzle. You're best to get a Helms
shop manual, otherwise you'll damage something getting it all apart.

 

In this model Accord, it isn't under the seat. If you fold down the
rear seat it should behind it. I didn't need to remove anything to
access it in this generation Accord.

 

Probably a bad sender unit in the tank. Older ones suffer from sulfur
corrosion badly. Took Honda a while to get them right.