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Fuel Gauge problem


primo74620

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The fuel gauge on my 74' 620 indicates that the fuel level is Empty. I checked the wire under the dash and my light tester blinked. I then went to the tank and it did the same. Is it normal for the tester to blink or should it stay On?

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The fuel gauge on my 74' 620 indicates that the fuel level is Empty. I checked the wire under the dash and my light tester blinked. I then went to the tank and it did the same. Is it normal for the tester to blink or should it stay On?

 

Ground out the wire going to the tank at the tank, the gauge should go to full, if it doesn't, then you have no power to the gauge or it could be bad.

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Ground out the wire going to the tank at the tank, the gauge should go to full, if it doesn't, then you have no power to the gauge or it could be bad.

 

ok, what does it mean if the gauge does go to full? and if it doesn't , does that mean that the sending unit is bad or the fuel gauge is bad?

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First, the temp and the fuel gauges are run of a small voltage regulator. If the temp gauge is working this is a good indication that the regulator is at least, working.

 

Power flows from the regulator through both gauges and to a sender that is grounded. Both senders vary a resistance to ground to vary the gauge reading. So if you ground the yellow sender wire, the gauge will read full tank.

 

If the gas gauge fails to read when the yellow wire is grounded it is likely broken somewhere between the tank and the gauge.

 

If the gauge reads full when the yellow wire is grounded (but fails to work when connected) then first check that the black wire from the sender does go to a good ground.

 

My guess is that the black ground wire is corroded or broken.

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Is it normal for the tester to blink

 

Yes, it is normal, because the instrument panel voltage regulator is a simple device that makes and breaks the connection slowly.

 

The testing procedure is as the other guys outline.

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Yes, it is normal, because the instrument panel voltage regulator is a simple device that makes and breaks the connection slowly.

 

The testing procedure is as the other guys outline.

 

Ok, thanks guys! I will be testing it today and I will post the results.

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Ok, thanks guys! I will be testing it today and I will post the results.

 

Alright guys, I just went out and grounded the yellow wire from the tank unit and the fuel gauge showed FULL. At what point do I start suspecting that the sending unit is bad?

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The second wire (black) on the tank sender has to go to a good ground.

 

Ground the black wire and the tank should read what ever is in it. If it does not read then you have exhausted every option and the sender is at fault or the float stuck.

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Float is sticking at that point. Drive it around and perhaps the sloshing gas will loosen it. I had a spare gas tank for my 710 and I pulled the sender and I guess the gas had dried up 20 years ago and everything looked like it was painted with an amber varnish. No way could you move the float up and down.

 

If you ever remove the tank you can take the sender out and maybe use a solvent on it to clean it? Either way, you know when you are getting low. :)

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Float is sticking at that point. Drive it around and perhaps the sloshing gas will loosen it. I had a spare gas tank for my 710 and I pulled the sender and I guess the gas had dried up 20 years ago and everything looked like it was painted with an amber varnish. No way could you move the float up and down.

 

If you ever remove the tank you can take the sender out and maybe use a solvent on it to clean it? Either way, you know when you are getting low. :)

 

I did remove the sending unit a few days ago and kept it connected and manually moved it up and down and the gauge read correctly. I suspect it may be hitting somewhere in the tank.

It also may be to long for the tank. Do you have any oics of what a sending unit for this truck should look like. I appreciate all your help Mike!!!!!!

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I did remove the sending unit a few days ago and kept it connected and manually moved it up and down and the gauge read correctly. I suspect it may be hitting somewhere in the tank.

It also may be to long for the tank. Do you have any oics of what a sending unit for this truck should look like. I appreciate all your help Mike!!!!!!

 

Well!!! I was able to get the senting unit to work properly. The arm on the float was hitting a piece of the body. I just simply bent the arm out a bit and presto!!!!!!!

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whats the part number for an oem fuel sender for datsun 620 pickup short bed?

 

25060 B5000 up to Aug. '74

25060 B8000 Sept '74

25060 B8001 Oct '74- Dec.'78

25060 B9800 Jan. '78-'79 short and KC.

25060 B8960 Jan. '78-'79 long and camper

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25060 B5000 up to Aug. '74

25060 B8000 Sept '74

25060 B8001 Oct '74- Dec.'78

25060 B9800 Jan. '78-'79 short and KC.

25060 B8960 Jan. '78-'79 long and camper

 

Jesus fuck, mike, how do you know all this shit all at once?

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