Rewiring! Ground the fuel sending unit?

[Dennis Detweiler]

Just replaced the tank in my 39 with a poly. Also, a new sending unit. The sender has two wire connector studs that go to the fuel guage. Do I need to ground the base of the sending unit? I assume I can be sure which wires go to the proper connector studs after I hook up the battery and the tank is empty? If the guage shows full, I need to reverse the wires?

I also added an electic fuel pump and will be using a relay along with an on off switch. I plan to use the electric pump to prime or if vapor locked. The mechanical pump is new. Carb is rebuilt.

Am I on course here?

I have to replace much of the cobbled shade tree re-wire job. I want to add relays to the heater, headlights, radio and anything else that's drawing a lot of current. Some wiring under the hood is still original and lost most of its insulation, so will replace it. The only relay I see on the 39 schematic is for the horn. I bought a 10 circuit marine fuse block. Someone put a handful of individual in-line fuse holders wadded up inside the dash with no labeling. Got to trace all of them and switch to the new fuse block. Wires are crimped together and crimped to connectors. It's a mess! I'm surprised everything works.

Edited May 11, 2018 by Dennis Detweiler
left out a word

[Plymouthy Adams]

yes....the two wires each travel to ground across the resistor via the wiper.....get a good clean ground on the sender and to the body and ensure that the ground from the engine to the chassis and also to the body is clean and tight

[Wiggo]

9 hours ago, Dennis Detweiler said:

Just replaced the tank in my 39 with a poly. Also, a new sending unit. The sender has two wire connector studs that go to the fuel guage. Do I need to ground the base of the sending unit? I assume I can be sure which wires go to the proper connector studs after I hook up the battery and the tank is empty? If the guage shows full, I need to reverse the wires?

I also added an electic fuel pump and will be using a relay along with an on off switch. I plan to use the electric pump to prime or if vapor locked. The mechanical pump is new. Carb is rebuilt.

Am I on course here?

I have to replace much of the cobbled shade tree re-wire job. I want to add relays to the heater, headlights, radio and anything else that's drawing a lot of current. Some wiring under the hood is still original and lost most of its insulation, so will replace it. The only relay I see on the 39 schematic is for the horn. I bought a 10 circuit marine fuse block. Someone put a handful of individual in-line fuse holders wadded up inside the dash with no labeling. Got to trace all of them and switch to the new fuse block. Wires are crimped together and crimped to connectors. It's a mess! I'm surprised everything works.

 

Dennis, do yourself a favour and buy one of the EZ Wiring kits (other brands are available). A colour-blind monkey had been employed at some stage to rewire my D20, using a random GM truck harness from a scrap yard. Maybe 15 or 20 unused and unlabelled circuits were just zip tied out of the way behind the dash, but still live and occasionally sparking out when they touched bodywork.. Where wires weren't long enough, another random colour wire had been crimped on, but the join hidden inside conduit or wrapped in electrical tape, so while you might start out looking for a blue wire with a white tracer, it may be dark green at the other end...

 

By far the easiest thing to do in the end was to rip out the entire harness - every last piece of wire on the car - and start from scratch. Every wire in the kit is labelled with it's name printed every few inches. An absolute joy to install. You need to be methodical and patient, but it is so much easier than trying to patch what is already there. I'd also recommend buying a kit of 1/4" multiway automotive connectors and the right crimp tool. This is a UK one, but you're bound to find a local supplier: https://www.12voltplanet.co.uk/26-piece-multiple-connector-block-terminal-kit.html

[vintage6t]

If you decide to start from scratch and use something like an ez-wire kit make sure it is compatible your car's voltage. In other words if your car is still 6 volts, you need a kit with wires sized for a 6 volt system. The wires on a 12 volt kit will be undersized in terms of carrying the current for 6 volt circuits.

[DrDoctor]

 . 

Edited May 21, 2018 by DrDoctor