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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: jamieaburch on October 25, 2016, 07:39:47 am

Title: Fuel Sending Unit Question
Post by: jamieaburch on October 25, 2016, 07:39:47 am

Just replaced fuel tank on my 79 and now fuel gauge reads empty. Is this a ground problem? The gauge was working before tank replacement. 

Title: Re: Fuel Sending Unit Question
Post by: hatzie on October 25, 2016, 08:59:22 am

The sender wire is shorted to ground or the sender has failed.

Title: Re: Fuel Sending Unit Question
Post by: jamieaburch on October 25, 2016, 09:07:56 am

When you say sender wire is that the power wire?

Title: Re: Fuel Sending Unit Question
Post by: ehjorten on October 25, 2016, 09:57:37 am

There is a ground wire that goes to the top flange of the frame rail for the sender.  Did that get connected when you replaced the fuel tank?

Title: Re: Fuel Sending Unit Question
Post by: jamieaburch on October 25, 2016, 10:06:15 am

I had to splice it back together and now I'm thinking it may have come loose when I put tank back in. Can I ground the wire to the frame or does it have to ground to the tank

Title: Re: Fuel Sending Unit Question
Post by: bd on October 25, 2016, 01:21:17 pm

An open ground will cause the fuel gauge needle to swing past full to about 3:00 o'clock.  As hatzie stated, for the gauge to register Empty, the signal lead is effectively grounded (either directly or through a faulty sending unit).  @Jamieaburch, the signal lead isn't actually a power lead, although it does have measurable voltage on it.  Make sure that you didn't accidentally splice the signal lead to ground.

Title: Re: Fuel Sending Unit Question
Post by: jamieaburch on October 25, 2016, 01:57:14 pm

Thanks bd. I will check when I get home