Gas Gauge problems- - The 1947 - Present Chevrolet & GMC Truck Message Board Network

tjvending · 07-03-2009, 07:00 PM

I'm still having problems with my Gas Gauge, I have read most of the other treads but still need to know my next steps. Here's what I've done:

New sending unit, New gauge from LMC, New wire from fuse box to sending unit on top of tank, Gauge seems to work, I'm getting a empty reading with key on, I took the wire off of both ends (Fuse block and Tank) both times the reading goes to full (3:00), Is the tank grounding itself at the top or is this OK? I can take the wire off and touch the sending plate and the reading will go back to empty, is this OK?

TJ

haysonj · 07-03-2009, 07:55 PM

Quote:

Originally Posted by tjvending

I'm still having problems with my Gas Gauge, I have read most of the other treads but still need to know my next steps. Here's what I've done:

New sending unit, New gauge from LMC, New wire from fuse box to sending unit on top of tank, Gauge seems to work, I'm getting a empty reading with key on, I took the wire off of both ends (Fuse block and Tank) both times the reading goes to full (3:00), Is the tank grounding itself at the top or is this OK? I can take the wire off and touch the sending plate and the reading will go back to empty, is this OK?

TJ

on mine the power goes to gage then from gage to tank to ground. You may have it wired wrong.

Hawker7 · 07-03-2009, 09:09 PM

I think that is the proper way to test it. Mine was not working at first after passing the tests you did. I then took the sending unit out of the tank and made sure the gauge would move when I moved the float up and down, and it did indeed work fine. I then noticed that the float was very close to the filter that is on the pickup line and it was getting hung up and not allowing it read past empty. I bent the line the float is on over a little and it worked great after that.

tjvending · 07-04-2009, 08:21 AM

I'm going yo take the sending unit back out and give it another try, will test the float like you said.

TJ

tjvending · 07-04-2009, 10:00 AM

Hawkwer7 is correct, I took out the sending unit, moved the float over a bit , did the testing to see if the gauge moved with the float, it did, replace the sending unit, it nows shows about 1/2 tank and stay there's with the key off. Is this correct, does the gauge read correct this way at the fuel level or does it suppose to go to empty with the key off?

TJ

Longhorn Man · 07-04-2009, 11:00 AM

some of them will drift a little, but for the best part, they stay put.

tjvending · 07-05-2009, 08:26 PM

I tought I had it fixed, It seem to be working with a half of tank (10Gal I put in a few days ago) I went to the gas station and put another 7 gal in and now the gauge is marked way pass full, at the 3 o'clok position, now what, should I pull out the sending unit again?

**LockDoc** · 07-05-2009, 09:32 PM

Quote:

Originally Posted by tjvending

I tought I had it fixed, It seem to be working with a half of tank (10Gal I put in a few days ago) I went to the gas station and put another 7 gal in and now the gauge is marked way pass full, at the 3 o'clok position, now what, should I pull out the sending unit again?

I would try a temporary ground wire with alligator clips on it from the tank to a bare metal spot on the dash and see what that does. There is also a ground wire from the back of the instrument cluster to the dash. You might check that.

LockDoc

tjvending · 07-06-2009, 11:51 AM

Where would the ground wire on the cluster be coming from, I see the main wiring hraness but no other loose wire, except for the shift indicator?

**VetteVet** · 07-06-2009, 02:19 PM

A 3:00 reading usually means that the gauge has lost it's grounding connection back through the sending unit to tank, to frame. Did you remember to plug the tan wire back into the fuse panel that goes to the sending unit?

Here's a neat little diagram to show how it all works.

**LockDoc** · 07-06-2009, 11:00 PM

Quote:

Originally Posted by tjvending

Where would the ground wire on the cluster be coming from, I see the main wiring hraness but no other loose wire, except for the shift indicator?

The ground wire is in the harness that plugs into the back of the cluster. It runs in the harness with the rest of the wires for 8-10 inches then is exposed and clips to the bottom flange of the dash. It is a Black wire with a funny looking end on it with no holes, and it just slides over a metal lip on the dash.

I hope this is as clear as mud...

LockDoc

peleni · 07-07-2009, 08:46 AM

I had a heck of a time getting mine fixed, symptoms were the gauge would stay at 1/4 tank no matter what I did. Replaced sending unit, same symptom.
I read every post I could find here in the forum and discovered there is one more component involved, the gas gauge resistor.
The sending unit should read from 0-90 ohms if you place a meter on it, the resistor on back of the gauge should ohm out at 90 ohms also (after you take it out of the cluster)...I have a stock 72.
When I replaced my resistor the gauge would go way past full when testing with the sending unit out. I reversed the resistor and everything started working fine. Something tells me there is more to that resistor than meets the eye. Hope this helps.

07-03-2009, 07:00 PM	#1
tjvending Registered User Join Date: Oct 2007 Location: rockville, md Posts: 257	Gas Gauge problems- I'm still having problems with my Gas Gauge, I have read most of the other treads but still need to know my next steps. Here's what I've done: New sending unit, New gauge from LMC, New wire from fuse box to sending unit on top of tank, Gauge seems to work, I'm getting a empty reading with key on, I took the wire off of both ends (Fuse block and Tank) both times the reading goes to full (3:00), Is the tank grounding itself at the top or is this OK? I can take the wire off and touch the sending plate and the reading will go back to empty, is this OK? TJ

07-03-2009, 09:09 PM	#3
Hawker7 Registered User Join Date: Jan 2008 Location: Raleigh, NC Posts: 321	Re: Gas Gauge problems- I think that is the proper way to test it. Mine was not working at first after passing the tests you did. I then took the sending unit out of the tank and made sure the gauge would move when I moved the float up and down, and it did indeed work fine. I then noticed that the float was very close to the filter that is on the pickup line and it was getting hung up and not allowing it read past empty. I bent the line the float is on over a little and it worked great after that.

07-04-2009, 08:21 AM	#4
tjvending Registered User Join Date: Oct 2007 Location: rockville, md Posts: 257	Re: Gas Gauge problems- I'm going yo take the sending unit back out and give it another try, will test the float like you said. TJ

07-04-2009, 10:00 AM	#5
tjvending Registered User Join Date: Oct 2007 Location: rockville, md Posts: 257	Re: Gas Gauge problems- Hawkwer7 is correct, I took out the sending unit, moved the float over a bit , did the testing to see if the gauge moved with the float, it did, replace the sending unit, it nows shows about 1/2 tank and stay there's with the key off. Is this correct, does the gauge read correct this way at the fuel level or does it suppose to go to empty with the key off? TJ Last edited by tjvending; 07-04-2009 at 10:01 AM.

07-04-2009, 11:00 AM	#6
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Gas Gauge problems- some of them will drift a little, but for the best part, they stay put.

07-05-2009, 08:26 PM	#7
tjvending Registered User Join Date: Oct 2007 Location: rockville, md Posts: 257	Re: Gas Gauge problems- I tought I had it fixed, It seem to be working with a half of tank (10Gal I put in a few days ago) I went to the gas station and put another 7 gal in and now the gauge is marked way pass full, at the 3 o'clok position, now what, should I pull out the sending unit again?

07-06-2009, 11:51 AM	#9
tjvending Registered User Join Date: Oct 2007 Location: rockville, md Posts: 257	Re: Gas Gauge problems- Where would the ground wire on the cluster be coming from, I see the main wiring hraness but no other loose wire, except for the shift indicator?

07-06-2009, 02:19 PM	#10
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,709	Re: Gas Gauge problems- A 3:00 reading usually means that the gauge has lost it's grounding connection back through the sending unit to tank, to frame. Did you remember to plug the tan wire back into the fuse panel that goes to the sending unit? Here's a neat little diagram to show how it all works. Attached Images __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

07-07-2009, 08:46 AM	#12
peleni Registered User Join Date: Apr 2009 Location: Austin, Texas Posts: 16	Re: Gas Gauge problems- I had a heck of a time getting mine fixed, symptoms were the gauge would stay at 1/4 tank no matter what I did. Replaced sending unit, same symptom. I read every post I could find here in the forum and discovered there is one more component involved, the gas gauge resistor. The sending unit should read from 0-90 ohms if you place a meter on it, the resistor on back of the gauge should ohm out at 90 ohms also (after you take it out of the cluster)...I have a stock 72. When I replaced my resistor the gauge would go way past full when testing with the sending unit out. I reversed the resistor and everything started working fine. Something tells me there is more to that resistor than meets the eye. Hope this helps.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.