• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Location of ground wire for BJ8

Share this page

T

Tomblin

Freshman Member
Country flag
Offline
While working on my fuel gauge, I have discovered that there is a fairly resistance (around 2 k ohms) between the ground wire and the frame. Given that the fuel gauge reads changes in resistance, this may be the source of my problems. Tracing this further, I found that this was true for all the ground wires serving the dash gauges and also the ground to the regulator and the overdrive relay. In contrast, my ohm meter shows very low resistance among all these grounding wires as I believe should be the case. The circuit diagram shows that the ground wire for the gauges, the regulator and the overdrive relay all share a common grounding point to the frame. My guess is that this is the source of the resistance. The problem is that I can't locate where this grounding point is. The ground wires disappear into the wire loom and I can't find where they join and connect to the frame. It would seem likely that this should be on the firewall, but I can't find any black wires tied to it. It could be under the dash, but before I try looking there, I'd like to know where to look. Of course, I could just tie each of the black wires to a new ground, but if possible I'd like to do it right.

Bruce Tomblin
 
Bruce,

Early or late BJ8?

The fuel gauge grounds via the sender through the tank hard connection to the fuel pump and chassis. This is iffy. It can help the gauge to run a ground wire in the trunk from the top plate of the fuel sender to the chassis.

If you don't have one, recommend the large color wiring diagrams from Tom's Import Toys:

WiringDiagramTomsToys.jpg

https://tomsimport.com/category/new-parts/wiring-diagrams/
 
Last edited:
I would add that working on a friends Healey that was having problems with starting, we finally tracked it down to the ground cable off the battery. The cable was so old it was corroded and even though I resoldered the end mount, it would not transfer enough power. New cable and the problem with starting was solved. I am sure it affected other grounds also.
 
Thanks for the thoughts. The sender has its own ground that is supposed to be through the tank. I agree that it is best to just run a wire from the sending unit to a good location on the frame. My problem is with the gauge which has its own ground that is common to the gauges and some switches on the dash. This circuit runs through the wiper switch and then to the common ground with the overdrive relay and the voltage regulator. This is the circuit that has too much resistance (I think). One the standard wiring diagram, you can see where these three circuits join to a common ground right next to the regulator. The problem is that the diagram doesn't show where this is actually located in the car.
 
Tomblin said:
Thanks for the thoughts. The sender has its own ground that is supposed to be through the tank. I agree that it is best to just run a wire from the sending unit to a good location on the frame. My problem is with the gauge which has its own ground that is common to the gauges and some switches on the dash. This circuit runs through the wiper switch and then to the common ground with the overdrive relay and the voltage regulator. This is the circuit that has too much resistance (I think). One the standard wiring diagram, you can see where these three circuits join to a common ground right next to the regulator. The problem is that the diagram doesn't show where this is actually located in the car.
Click to expand...

I didn't like that lengthy path to ground so I made a small grounding harness which links at least one mounting screw from each gauge to a new dedicated ground screw tapped into the windshield wiper motor mount. Also added a direct ground from wiper motor to this screw.

screenshot.1967.jpg
 
A

All the suggestions made by steveg are in line with correcting the fuel senders grounding problem , install em OK
 
I agree. I just tied the grounding wire to the frame as recommended by Steve. Now I have a functional ground for the gauges etc. Also, I agree that the sending unit also needs a grounding strap from the unit to the frame rather than relying on the tank to do this. The big lesson I learned was that when you have an electrical problem check that the ground in the circuit is solid.
 
Back
Top