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2000 Honda Civic EX (Coupe)
Hello all, so a while ago I noticed my fuel gauge started acting funny. I use my tripometer religiously and always knew it was at 1/4 tank of gas at 284 miles, well it started saying before or around 284 miles it was really low on gas, like the needle would go to E and the low light barely ever came on. But I would freak out and go to fill up and there would be about 4 gallons left still. So I asked about it up here and everyone said replace/test the fuel sending unit. Well, I finally got around to getting a new one (OEM) and installed it and also changed out my fuel filter as well. I had the car low on gas when I installed the fuel sending unit and I started it up after and it was fine. I drove it a few miles to the gas station to fill it up fully, but as I was leaving my neighborhood the low fuel light kinda flashed on for about a second or two and then went back out. I didn't see it come on anymore after that. So here I am at the low gas level again, and it was nearing E but the light kept coming on and off and on again. Just randomly and over and over. When I put gas in it, it took 10.3 gallons. I don't recall what would happen when my low fuel light actually worked properly and what it would do. I've had the car for about 5 years and I usually don't run it down that low anyway. I usually fill up at 1/4 tank left and around 284 miles. I just did this the last 2 times to test out the light as well. So is it coming on like this normal? It's kind of annoying so far.

Also, I have always had the problem that when my car is low on gas (again around a 1/4 of a tank) it takes a few seconds longer to start up at a cold start. Usually with a fuller tank it only takes one second and seems normal, but with the fuel low it will definitely take longer. Is this also normal or a sign of something else? Thanks for any info!

 
Rep Power: 518

I don't own or drive one, so I'm just using service info for this

The low fuel sensor is described as a thermistor, so it should be slow to react to fuel slosh. The info describes it taking up to minutes to change states.

If your light is blinking then I might wonder if you got a wire pinched or an exposed wire is getting grounded against metal.




Long cranking time when the tank is low, that's been pretty much average on an awful lot of the cars.
My Buick was far worse than any of the Hondas I've seen though. Sometimes I had to let it roll to flat ground before it would start.

 
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I have read the service manual on how to test it and all but I didn't really understand, electrical work is nowhere near my strong subject for cars. Luckily its my dad's. But he's read it over and over and seemed kind of perplexed by the test instructions as well. I guess it left out a step and this was from the factory service manual. Anyway, he is looking into it...I don't know what's going on at this point.

We both read where it said it could take up to 4 minutes to show it being low on gas? I will look more into it tomorrow morning.

 
Rep Power: 518

Oh damn, I left out the 4 in my post. Oh well.

I gathered that the low fuel sensor controls the light directly, and the sensor controls the delay time for the light to illuminate. (This keeps the light from coming on every time you go around a corner with a half tank.)

If you ground that wire at the connector on top of the tank, the light lights immediately.
If something else grounds that wire anywhere between the gauge and the sensor bulb inside the tank, the light comes on immediately.


If you lift the tank unit out so the sensor is no longer submerged in fuel, the light should take up to 4 min to come on. Same when you submerge it again. It should not be immediately lighting the bulb if the sensor is controlling it (and working properly).


GUESS (since I can't actually see one in front of me):
If something got bent far enough that the float arm is making contact with the exposed part of the terminal or wire on that sensor (only when the fuel is low enough to let the float drop), it might make the light come on immediately.

It's all I got right now. HTH

 
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Sorry I've gotten pretty busy lately and it's really cold as well. I am going to let it run down to about a 1/4 and see how it works again and then open it back up and try to do some checks/tests. Will keep you updated.

 
Rep Power: 518

Idea:

Fill a gas can (2-5 gallon?), get a funnel if needed, put it in the trunk (safely), then drive it until you run out of gas.

That should answer the questions of when the low fuel light will come on and how much gas is actually left when the light does come on.

Then dump in the gas can and head for the filling station. LOL

 
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Yeahhhh, sorry how about no on that one...I haven't gotten it so low the gas light is coming on yet but it's about 1/4 of a tank now. What sucks is my tripometer has been screwing up too, it's hard to reset at fill-ups, I basically have to mash the button and pray it will zero out. Anyway I was planning on replacing that too very soon. My dad drew out his own wiring diagram and said the old one did act screwy at one point, I still haven't pulled out the new one. It's 45 degrees today so maybe I will do it today and get him to test the new one and I will try to clean up the one ground terminal tab thing...