low fuel gas gauge

[john lewis]

hi the low fuel light would stay on and gas gauge would stay on E so i went under car cleaned contacts and it stayed same, i changed wires around on sender at gas tank, light went out and gauge went to F but it doesnt seem to come down, i have put in around 26 liters which should have shown about half tank but it was still hard on F any ideas what i should do to get gauge working right also do u know how low u must go in gas to have low fuel light come on if that is working i may be ok without gauge, thanking u in advance john

[jclay (RIP 2018)]

The sender is really a potentiometer. It builds a resistance in the sender which the gauge reads. The lower the fuel the more resistance.

You Green/Black wire are shorted to ground somewhere. I suspect that you might have put the wires on the wrong connection at the switch.
There are three wires.
Black to ground.
Green/Black to the gauge.
Green/Orange goes to the low fuel light.

The Green/Orange wire goes to the low fuel switch in the sender. There is a delay unit in the line that keeps the light from blinking when you turn corners and move the fuel around.

jclay

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[john lewis]

i will look today at the way i got wires at switch but when i hook them up the other way the light stays on and gauge reads empty, 1 short could affect both i figured the wires were ok when light went out and gauge came up ill crawl under today and look thanks

[john lewis]

i have looked at wiring green black is going to gauge green orange to light so hopefully my light will come on when gas is low i checked gr. bl. wire for short as far as i could see which wasnt very far see no problem maybe it is working but needs to go down further to show on gauge (call that hopefull thinking) ill wait and see hopefully i will not run out of gas i have once so far but i was leaking it pretty bad i got only 100 miles on tank since i have fixed leaks @ fuel pump, feed from tank, overflow to chacoal filter from flooding so bad hoping to get 300 miles to tank that isnt unreasonable is it

[Rich in Vancouver]

Rather than just swapping wires I would refer to a wiring diagram or to photos of another car if someone has them available. Disconnect the warning light wire as it isn't essential and get the guage working first. Then sort out the warning light. Use an ohmmeter to check the continuity of the wires but it is more likely that wires are in the wrong rather positions than broken.
Good luck! It can be really frustrating, but a systematic approach will solve the problem.

1975 TR7 ACL764U

[jclay (RIP 2018)]

Disconnect the Green/Black wire and see if the gauge goes to empty when the key is on. Then ground the wire and see if it goes to full.

If it does that, then the circuit is good and you just have the wires miss connected.

You know the sender could be bad, full of gas, and you have the green wires switched. That would cause the condition.

jclay

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[FI Spyder]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by jclay</i>


You know the sender could be bad, full of gas, and you have the green wires switched. That would cause the condition.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

That's what I was thinking. While you pull the sender out of the tank to check the float, it would be a good time to check the condition of the bottom of the tank for rust, water. A new rubber seal might be in order as the old one might not reseal properly.

John, you should get over 300 miles per "tank". I got over well over 400 miles but it depends on traffic conditions (stop and go), highway speeds, shift points, the weight of your right foot[:)], and any hypermilage techniques you might use.

TR7 Spider - 1978 Spifire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra

[john lewis]

when i disconect gr. bl wire from tank and turn key on gauge reads E when i hook it up again it reads full i never tried to ground wire i will tomorrow let u know if it reads F or E it is a new tank and a new sender from the looks of it and what i was told by guy i bought car from,with the other wire hooked up to low fuel light should it work even if gauge doesnt,i think wire is good because light was on before i switched wires thanks john

[john lewis]

couldnt wait until tomorrow went out and crawled under her now when i disconect gr.bl. wire gauge goes to E when i ground gauge goes to F then when i reconect gauge goes to F i have about 50 miles on this tank maybe it must go lower to register ,the sender is shinney and it looks new i will try to drive and see what happens to gauge but i see what u mean now i must have a bad ground on gr.bl. wire thanks john

[jclay (RIP 2018)]

That is the way it should work. The problem is with the sending unit.


jclay

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[john lewis]

do u think low fuel light will work or does it work off same sender

[jclay (RIP 2018)]

Two switches in the same sender. Take the sender out and hook up the wires. Move the float up and down and see if it makes a difference. At the same time you can check to see if the float is full of fuel.

jclay

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[Rich in Vancouver]

In the mean time carry a gallon can of gas with you. [:)]

1975 TR7 ACL764U

[john lewis]

well yesterday i had my gas shower when i got sender out float was stuck after a 1/4 can of peneterating and hr of moving up and down it broke free when i put it back the needle sort of bounces around as if it doesnt have the delay that was mentioned earlier,i tried switching them around got no reading i will keep an eye on it to see if it is actually working

[PeterTR7V8]

My needle bounces too. I suspect the delay thing is either a myth or Lucas made it.


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