fuel guage reading question

[76Datsun280z]

You know how when the ignition isn't off and the fuel guage reading is all the way to the left side of the guage past the "E" mark? I was kind of curious if this is how far the line actually goes until the tank is completely out of fuel, something I'm not going to try but was curious about.

[76Datsun280z]

Sorry about that, I meant to say in the first sentence "when the ignition is off".

[JimmyZ]

When you say "I'm not going to try" it implies that you know it's bad for your pump to run dry or intermittently dry.

I imagine "E" is different for each car by a small degree. If you have a drain plug on your tank you can always drain and see. Just add about a gallon, look at the guage and consider that a bare minimum. (pref more for FI) The angle the car is sitting at also has an effect on how much fuel is getting to the pickup tube. When my 71 has run out of gas if I'm on level ground it takes about a gallon poured in to get going again. It takes two gallons if it's on an incline. When I was younger I used to run out of gas but that ended in my mid twenties.

My car is a '71 and has a different tank of course but here's a page I made for it. At the end of the page are some pics of the inside of the tank and the pickup tube. The baffles can hold fuel away from the pickup if you should corner hard. Keep that in mind if running low.

http://warbuddies.homestead.com/gastank.html

2c

Jim

[sblake01]

It doesn't hurt the EFI fuel pump to run it dry. They're self-priming. May take a minute or so to start after you put gas in but it will start. BTDT! Also on my 78 (as well as on my 810) there's a low fuel light. I thought the 75-76 has that also. When I see that thing glowing red I don't waste time getting to a gas station. I've never really took the time figure out how much gas is left when it comes on but I'm sure it couldn't be more than about 1-1/2 gallons. At that point the needle is below the 'E' mark but not as far left as when the key is off.

[JimmyZ]

Blake you might be right on this one regarding 280Z pumps...

I know that on new cars the fuel pump relies on the gas for cooling and "lubrication". This is definitely true on in-tank pumps and to a lesser degree on ext pumps. I'm not saying that running it dry once or twice will kill a pump but it will shorten it's life. It's my understanding that when you run a centrifugal pump dry that the inside rotor may contact the bore and wear on the tolerances. (Things are spinning pretty fast in there) The effect is like having a worn oil pump. When things get worn to a point it won't be able to put out the volume/pressure it once did. When running a tank low sediment/contaminant concentration becomes greater giving the pump internals something to chew on. (=NG)

Mechanical pumps don't mind going dry.

2c

Jim

[76Datsun280z]

Interesting, thanks for the responses guys!

[sblake01]

Well, I did only do it once. That was at least two years ago and I've had no problems with it since then. I can understand that making it a habit would shorten it's life.

[Rockr69]

Stephn you're right about the 76 fuel light. MIne doesn't work, but to 76280z, when my gas gauge says E I can interpret that as "get to station dumbass before you leave me stranded out here alone!". That would be the car talking to me. Well she doesn't really talk. At least others have said they can't hear her....OK Bye now:ermm:

[sblake01]

They're (the fuel light) pretty easy to fix. Just pull the sender and clean the contacts for the fuel light sensor attached to the float. It's pretty self-explainatory once you've got the sender out.

[TomoHawk]

Higuys

I checked my fuel gauge last summer by driving up & down the freeway when I was close to empty with an extra gallon of gas with me. When it got very close to E, I got off the highway and drove around in the burbs until the engine just started sputtering. Then I put in the gallon and went to the next gas station. On my car, Empty was right at the E, or just a hair after. This shows that it's importantto keep the electrical connections for the fuel gauge in very good condition so the gauge reads correctly.

I would like to know more about getting the the warning light to work. All I know so far is that one wire to the light is hot with the ignition.

thxZ

[sblake01]

I got mine to work by removing the sending unit and cleaning the contacts at the upper end on the float rod where it rides across the resistence bar or whatever you call that and checking for continuity at the warning light sensor connections when the float is all the way down. It has to be done carefully. Dont bend anything while youre working with the sending unit/float assembly. Once you have it out, like I said eariler, its fairly self-explanitory. Of course, make sure the bulb in the warning light is good before doing any of this.

[280~Master]

After trying to clean my tank, which I did get done. I placed the car on level ground and added gas at 1 gal intervals. It took 4 gal to start. Remind you this is from a bone dry tank. So when you run out of gas you really have 3 gal left at the bottom of the tank. So I guess you could run the car down to a low level and drain the gas out then add gas untill it starts and read your gauge to find out your lowest level on your gauge.