Jump to content

That darn fuel gauge


SUNRADER LANDON

Recommended Posts

Looking for a fix for the fuel gauge. I pulled apart my cluster, cleaned up some connections, and upon reinstall, I noticed the needle moved slightly, whereas before it wasn't moving at all.

I checked the connections with voltmeter. I believe I was only reading .5 v. Also checked all my fuses. All good. Anyone have similar issues/ potential fix?

  • Like 1
Link to comment
  • Replies 21
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Flatimus,

 

Thanks for the response! I did run out of gas the other day...so there's that.

 

I'm guessing the sending unit is in the tank? The connection would be at the top of the tank? In other words I'd have to drop my tank?

 

Also pulled the cluster to look at the gauge (had no clue what I was looking at) what does the volt reg look like and how would I go about fixing it?

 

Thanks again

  • Like 1
Link to comment

I don't know much about 720s so my knowledge to help will be pretty general.

 

Find a factory service manual online.

So invaluable in helping you diag the components and give proper values when testing.

 

 

 

On my 521, I have a pop out panel in the bed that opens to the fuel level sending unit. But yes, it is on top of the gas tank.

  • Like 1
Link to comment

I have the '84 FSM and will look that up when I get home. The tank sender resistance varies from 10 ohm (full) to 80 ohm (empty). The gauge cluster has a voltage regulator that provides a constant 8 volts so the gauge does not change when running at 14.5 volts and with the key off at 12.6 volts. Not sure on the 720 if the regulator runs both the temp and the gas gauges. (it does on earlier Datsuns) It's easy enough to take out and clean the contacts with fine emery paper.

  • Like 1
Link to comment

Looks like a set of points, and as such they can corrode or get dirty and just stop working. It's a bi metallic strip with a wire coiled around it and contacts on the end. When there is contact current warms the metal strip and it bends away and the contacts separate. It cools and makes contact and just keeps repeating this.

 

Here's mine...

720fueltempgaugevoltregulator002Large.jp

 

There may be one for each gauge. A reference gauge setting is input and the regulator adjusted to read 1/2 or full or what ever it is.

 

 

Just get some super fine emery paper and fold a thin strip so it's abrasive on both sides. Pull the contacts open, place the strip between the points, let them close on the paper, and slowly pull the paper out from between. This will polish the contact surfaces.

  • Like 1
Link to comment

It's at the very top in the picture. There is a small white wire coiled around the bi-metallic strip. (two dissimilar metals that when heated, expand at different rates and will tend to bend) At the far right of the strip is a pair of contacts, almost like ignition points...

 

003.jpg

  • Like 1
Link to comment

I own a steel Emery board.

 

It's a bit thicker than a 1/16" of on inch with fine knurling on both sides. Even has a point on the end I use as a pick.

 

 

I remember as a kid my mom using one of these for her nails.

 

I love it. Great tool in my box. Many uses.

I have no clue if they can still be bought.

  • Like 1
Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.