gas gauge - interesting one here.....

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71coupe

Well-known member
Joined
Feb 14, 2011
Messages
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Location
New Braunfels Tx
My Car
1971 mustang
I have an interesting one here...well maybe...

Car is:

'71 Coupe

302

Problem: gas gauge wasn't reading

fix: put in new sending unit.

Issue: when I put the key in ignition (ACC) the gauge reads fine. But, when I start the car the gauge reads empty. :huh:

Anybody know why this is happening? Thanks!

 
Does it happen with the key in RUN only (engine not working)? My suspicion is that it won't. Something is wrong with your ignition switch (which ultimately powers up the constant voltage regulator) or the lead to the dash cluster for the same (something is drawing the voltage down while the car is running).

 
Jim, is that a guess? It doesn't make sense to me with his scenario. I'm leaning toward a bad ignition switch. Where as the regulator is properly feed while in the accessory position but the switch being defective on the post that feeds the regulator during the run position. Any thoughts guys.

 
I ran out of fuel one day in the middle of nowhere because my gauge read "full"...

I had put the wires on back to front....

It's easy to do ...try first before mucking around with other stuff...

Putting the sender in upside down will effectively cause the same result as switching connections...

It's been a few years since I restored the tank ...not sure if you can even put it in upside down....

 
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As "Will e" is pertaining to, Having said that, I would recommend to everyone to get rid of the original stlyle CVR and swap it for an electronic one...

They are just as cheaply and badly designed as our ammeter gauges...

Pretty sure the fuel and oil gauges are 6v also.

 
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I think the key here is that it functions correctly in one position ( the accessory position) And does not function at all in the other(the run position). The others are correct, if you have center gauges-the engine temperature and oil pressure will be operating incorrectly and similar to the fuel gauge(under this bad switch scenario).

If you have standard dash gauges, the fuel tank sensor is the only one feed by the regulator circuit.

 
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