Fuel sending unit electrical connections

[npdw]

Hi all,

the old gas tank for my normal '72 carburated bmw 2002 was too rusty to work with. The fuel sending unit was also broken with parts missing. Therefore I started looking for a 2nd hand gas tank to replace it with. I found one, but it is slightly different:

1. It is a bit higher, so the fuel sending unit is just too high compared to the floor....
2. The connections where it is attached to the body do not line up for 2 or 3 holes
3. The fuel sending unit has only 2 electrical connection pins, where the original unit had 3 pins!

 

I think I can solve issue #1 and #2 but for #3 I have no idea. See attached the original fuel sending unit with 3 connection pins, now I only have 2 connection pins. However, from my wiring harness I still have 3 cables.....the ground cable/connections pin is easily to match, but what to do with the other 2 cables from the harness? I only have one connection pin left!!...

 

Maybe I have to look for another gas tank?

 

gr, niels

 

 

Edited May 12, 2019 by npdw

[Simeon]

The ‘third’ connection is related to a low fuel light (using the large red light on the instrument binnacle). If you leave it disconnected (I would insulate it well do you don’t get an occasional flicker) it will have no negative impact. 

 

Oh, and get some hose clamps on your fuel line. Clamp all joints in the truck and any under the hood as the hose goes to the carb. 

Edited May 12, 2019 by Simeon

[Mike Self]

17 hours ago, Simeon said:

the ‘third’ connection is related to a low fuel light (using the large red light on the instrument binnacle).

Simon, US spec cars don't have that low fuel warning light--that big red light on the dash is given over to low brake fluid warning, and our sender units only have two terminals.

 

mike

[npdw]

My car is european, any ideas?

[npdw]

I think I have the solution. My replacement tank is 51 liters altough I used to have 46 liters original. 

 

I have to look for an original one with 46 liters. 

[Simeon]

If you can find one. 

 

I have a similar combination, you need to put > 10 litres in the tank before the gauge will move off empty. I would like to fix this but the cost of tanks and senders is more that’s I want to pay (not complaining!). 

[dlacey]

On 5/13/2019 at 7:13 AM, mike said:

Simon, US spec cars don't have that low fuel warning light--that big red light on the dash is given over to low brake fluid warning, and our sender units only have two terminals.

 

mike

Never knew that, I thought the big red light was a general 'something is wrong' light... And then you are meant to pull out the manual like an aircraft copilot and go thru the checklist to identify the fault...

[BarrettN]

12 hours ago, npdw said:

My car is european, any ideas?

Any chance you can disassemble the old sending unit and graft the low fuel contact and leads onto a new sender? I tore open an old sending unit and rebuilt it - pm me a pic if what's left of your old sensor and maybe with that I can give a better opinion of your options. 

[Simeon]

From memory, one of the side shafts that carry the float is insulated from the body at the top and connected to the terminal at the top. The other is grounded to the body of the sender. A simple brass contact on the float connects the two together when it is right at the bottom of its travel.