Fule pump / Sending unit problems

[readymix]

Well i removed the bed and the sending unit from my 87 to see what was wrong and the thing was all normal. 3 Ohms at empty and 94 Ohms at full. I did find that the sending unit and pump are only recieving about 6Vdc input and i though this could be the cause of my faulty fuel gauge readings. What do you guys think.

I know the gauge works fine because when the sender is removed from the loop the gauge reads full but when it is plugged in the gauge will never read above 3/8 tankwihte the sender at full???
Any suggestions.

 

[dyeager535]

I'd find out why you are only getting 6V to the sending unit. Seems odd to be only 6V, for sure. Guaranteed it should be 12. Check the other end of that wire to make sure it's not getting 12V either.

 

[4X4HIGH]

Also, GM sending units are 0-90 ohm. I don't know how big a difference the 3-94 ohm you are getting will make but the sending unit itself usually says the ohm range right on them. Also GM uses grounds to activate things, so if the sending unit wire were to be grounded the gauge would read full.