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Gas Gauge Not Working


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#1 NWmonte71

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Posted 07 March 2017 - 02:38 PM

I just purchased a 71 Monte Carlo and the gas gauge needle is stuck past "F". The needle does not move with key on or off, it seems to be stuck in that one position. I was wondering if anyone else has experienced a similar situation with their gauge. I am wondering what side of the circuit I should start at first for troubleshooting.........sending unit near the tank or back of the gauge?  Any troubleshooting tips would be greatly appreciated. 


sml_gallery_5838_288_247210.jpg1971 Monte Carlo, #'s matching 350cid with TH350, Factory "Lime Green" with original "Antique White" painted top.


#2 Leghome

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Posted 07 March 2017 - 04:02 PM

The first thing I would check would be the ground. After that someone else will have to help out.


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#3 Rock

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Posted 07 March 2017 - 05:04 PM

I had to replace the sending unit. Mine always read past F too. After all the trouble shooting it was the only logical piece.
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#4 NWmonte71

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Posted 07 March 2017 - 10:06 PM

I had to replace the sending unit. Mine always read past F too. After all the trouble shooting it was the only logical piece.

I assume you have to drop the tank to get to the sending unit? No access hole on the bottom of the trunk pan?


sml_gallery_5838_288_247210.jpg1971 Monte Carlo, #'s matching 350cid with TH350, Factory "Lime Green" with original "Antique White" painted top.


#5 71MonteCarloMD

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Posted 08 March 2017 - 05:26 AM

Yes, would need to drop the tank to replace sending unit. Maybe you can check ground wire from top of tank to see if it's secured to body?

#6 72-CLASSIC_RIDE

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Posted 08 March 2017 - 05:55 AM

Yes Chris,  you have to remove Gas Tank to access Sending Unit.  Again, check/clean Ground Contact(s) 1st.  

If you will need replacing Sending Unit, be advised there is/was a thread that talks about problem(s) with aftermarket Sending Units operation.  Some adjustment (tweaking Sending Unit) was necessary during installation to get Sending Unit to read correctly.  If you need a Sending Unit,  this thread or someone who has experienced replacement can guide you to correct Sending Unit or how to adjust aftermarket one to read correctly..

 

http://www.firstgenm...es/#entry173625

 

Hope this helps.

 

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#7 Rock

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Posted 08 March 2017 - 08:11 AM

With the car in run mode but not running you can ground the brown wire in the trunk of the car and the gauge should go to empty. Now for some reason when I did this trouble shooting step my gauge never changed in my car. Not sure why. Theoretically it should drop to empty. I ended up dropping the tank and replacing the tank, sending unit,straps and all vent hoses. It all needed to be done anyways.
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#8 NWmonte71

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Posted 13 May 2017 - 07:57 PM

I am interested in starting off with a clean/fresh tank for the cleanest fuel delivery possible. Where are most people buying their OEM replacement tanks & sending units? I know Original Parts Group sells them........anyone else you suggest? I want to replace the tank, sending unit, steel lines, and rubber hose connections all at once.  


sml_gallery_5838_288_247210.jpg1971 Monte Carlo, #'s matching 350cid with TH350, Factory "Lime Green" with original "Antique White" painted top.


#9 NWmonte71

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Posted 27 June 2017 - 09:39 PM

I am interested in starting off with a clean/fresh tank for the cleanest fuel delivery possible. Where are most people buying their OEM replacement tanks & sending units? I know Original Parts Group sells them........anyone else you suggest? I want to replace the tank, sending unit, steel lines, and rubber hose connections all at once.  

Thought I'd bump this topic back up............ Where is everyone buying their replacement sending units? I see tons of new ones on Ebay, but not sure if they are just cheap junk?


sml_gallery_5838_288_247210.jpg1971 Monte Carlo, #'s matching 350cid with TH350, Factory "Lime Green" with original "Antique White" painted top.


#10 NWmonte71

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Posted 23 August 2017 - 07:10 PM

I just completed my new sending unit install. The gauge now works as designed!  Feels great to know how much fuel I am consuming on cruises. The install was very easy, the hardest part was installing the tank with the straps. I ended up buying a new sending unit on Ebay from Abodies.com 


sml_gallery_5838_288_247210.jpg1971 Monte Carlo, #'s matching 350cid with TH350, Factory "Lime Green" with original "Antique White" painted top.


#11 NWmonte71

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Posted 10 September 2017 - 08:23 PM

Well, I spoke too soon on a positive outcome............. new sending unit is stuck at 1/4 tank. I installed the sending unit a few weeks ago and filled the tank with approximately 1/4 tank of fuel. The needle has been in this position for over 300 miles of driving! I figured maybe you get what you pay for with sending units and I bought an averaged priced one. I talked to another 1st gen owner this weekend, he told me that his new sending unit was getting "stuck" and that he had to bend the float arm to make it work correctly. Anyone else experience this or have heard of this? I'm bummed out that I have to transfer all the fuel back out and drop the tank again. What should I do?


sml_gallery_5838_288_247210.jpg1971 Monte Carlo, #'s matching 350cid with TH350, Factory "Lime Green" with original "Antique White" painted top.


#12 72-CLASSIC_RIDE

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Posted 10 September 2017 - 11:05 PM

I have heard that same problem in many previous discussions.  Seems to be rather common now when changing Unit.  I can't remember if it was determined someone found a solution on a Sending Unit that worked without modification.  

Hopefully they will reply if seeing your message.

 

Doug.


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#13 stangeba

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Posted 11 September 2017 - 06:14 AM

I just found this write up. I don't remember who deserves the credit.

Fuel Gauge Problem Diagnosis:                                                                                              15 Mar 2013

This process can be applied to all recent GM cars except those with computerized gauges.

1) Locate the fuel sender feed wire near the fuel tank. You're looking for a single tan colored wire. With the tan wire disconnected at the fuel tank, the fuel gauge should read past full with the ignition on. Wait a few moments as some fuel gauges take a long time to respond. Touch the tan wire from the body to any convenient ground and the gauge should read empty. If not, you have a wiring problem or a bad gauge.

2) If the gauge responds correctly, the gauge and wiring are OK. Next use a multi-meter to measure resistance to ground of the sender wire connection on the top of the fuel sender or the tan wire from the top of the fuel tank. Measurements should track the fuel in tank.

Full - 84-88 ohms

Half - 40 ohms, give or take

Empty - 0-2 ohms

If this doesn't check, then sender or wiring on top of the tank is bad or the sender not adequately grounded. Senders are typically grounded by a black wire which is welded to the sender and attached to the body with a sheet metal screw.

3) If the sender checks OK but gauge and wiring don't, clean the connections, reconnect the sender wiring and separate the Fisher connector (located just outboard of the fuse block under the dash). The gauge should then read past full. Ground the tan wire in the dash side of the Fisher connector and the gauge should read empty. If not, you probably have a bad gauge or possibly a dash wiring problem. Go to Step 5.

4) If the gauge checks OK, then make the same resistance checks to the tan wire in the body side of the Fisher connector. If the readings are different than those at the sender, body wiring has a problem and requires detailed inspection. If they look OK, then the Fisher connector is probably dirty.

5) Clean and reconnect Fisher connector, pull the connector off the back of the gauge and make the same resistance checks to the tan wire. If they don't check, you have a dash wiring problem. If they check OK, your gauge is bad. Gauges can be bench-checked but this is best left to a specialist.


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#14 71MonteCarloMD

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Posted 11 September 2017 - 11:22 AM

Ditto on Bruces post as I used multi-meter to ensure measurement of the reader. Works like a charm for 5 years now.

#15 John S

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Posted 11 September 2017 - 03:31 PM

Couple years back I encountered same problem. Installed three new sending units all repops. None of them worked. The last one was AC Delco brand. Fortunately I was able to borrow a borescope from where I work and found float resting on bottom of tank with 1/2 tank of gas in it. With those pictures I was able to get refund. I got lucky The Parts Place had one NOS sending unit left $229.00. Works fine no problems. Now I know that there not any NOS ones around so unfortunately it's hoping you get lucky. All I can think of is buying one from a reputable company, even if it costs more, that will stand behind it. And yes it is frustrating draining gas and removing tank, I know I did it four times.

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#16 NWmonte71

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Posted 11 September 2017 - 08:11 PM

Couple years back I encountered same problem. Installed three new sending units all repops. None of them worked. The last one was AC Delco brand. Fortunately I was able to borrow a borescope from where I work and found float resting on bottom of tank with 1/2 tank of gas in it. With those pictures I was able to get refund. I got lucky The Parts Place had one NOS sending unit left $229.00. Works fine no problems. Now I know that there not any NOS ones around so unfortunately it's hoping you get lucky. All I can think of is buying one from a reputable company, even if it costs more, that will stand behind it. And yes it is frustrating draining gas and removing tank, I know I did it four times.

John S

John, I jumped over to another forum last night (Chevelles.com). I read many articles about failing re-pop sending units. Many folks ended up going through 2-3 units before getting one that worked correctly. I finding it amazing at how many classic GM vehicles exist in the U.S. and have been restored...........what is the consensus for the go-to company for sending units? Surely there are not enough NOS units in existence to supply the demand? I read also people having issues with the re-pop floats actually floating in fuel. One guy actually said he tested a new unit and the float sunk in fuel, but floated in water!  Crazy. I guess maybe I will buy one from a well known company that is willing to refund me if an issue occurs. 


sml_gallery_5838_288_247210.jpg1971 Monte Carlo, #'s matching 350cid with TH350, Factory "Lime Green" with original "Antique White" painted top.


#17 Shnalla

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Posted 12 September 2017 - 09:43 AM

Last year, I ended up replacing my sending unit with a new one from rockauto on my 72.

Problem solved.


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#18 NWmonte71

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Posted 12 September 2017 - 05:49 PM

Last year, I ended up replacing my sending unit with a new one from rockauto on my 72.

Problem solved.

I assume you just dropped it right into the tank with no fiddling around worked first time?


sml_gallery_5838_288_247210.jpg1971 Monte Carlo, #'s matching 350cid with TH350, Factory "Lime Green" with original "Antique White" painted top.


#19 Rock

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Posted 12 September 2017 - 07:38 PM

https://www.rockauto...nding unit,4436
This is the one I bought. No problems. Mine had a return line you may have one or not.
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#20 Rock

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Posted 12 September 2017 - 07:38 PM

https://www.rockauto...nding unit,4436
This is the one I bought. No problems. Mine had a return line you may have one or not.
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Nothing special about this Monte. No SS, no rare options just a super sweet car to drive and take me back to the good old days!




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