1973 BMW Tii - Fuel Sending Unit

[Billsmith]

My gas gauge is not working and I may need a new sending unit.  Am reading on the forum and troubleshooting now.  Thanks to those who have posted on this topic in the past.  My question:  For a 1973 Tii, do I need the 200 mm sending unit used on the base model that year or is there a 223 mm unit specifically used on the Tii.

 

I found this one but it may be too short for the Tii.

 

https://www.rogerstii.com/bmw-2002-fuel-level-sending-unit-1971-73/. My car was manufactured in March of 1973.

 

Any advice will be appreciated.  Thanks.

[Conserv]

I’ve summarized the relevant part numbers for the three (U.S.) tii fuel tanks and their ancillaries. Assuming your car’s VIN is from 2761963 through 2764521, yours should be a Type II fuel tank. But all U.S.-spec round taillight tii’s share the same fuel sender, regardless of whether Type I or Type II tanks.

 

You should confirm, however, that your car still has its original fuel tank. It would have had a screw-down style of fuel pickup but not the cropped right rear corner of a square taillight tank.

 

Regards,

 

Steve

 

[dlacey]

The tii one is longer and has 2 electrical connections on-top ...in addition is doesnt have the fuel pickup.

 

The one you show seems to have a fuel pickup and a single fuel gauge connection.  It wont work properly in a tii.

 

The two electrical connections are for fuel level and low fuel warning, the tii device is a pure sender unit....no dual-function fuel pickup as on carb cars. 

[BarrettN]

I still have resistance wire if needed - look for my write-up on rebuilding senders.

[Billsmith]

Thanks for the prompt response.  I am a true novice.  Please check out these photos of my tank and keep me out of trouble.

Thanks,  Bill

[Billsmith]

VIN number is 2763563

[Conserv]

9 hours ago, Billsmith said:

VIN number is 2763563

And that is, indeed, a round taillight tii tank of the correct original type for VIN’s 2761963 through 2764521 (having screw-down fuel pickup). It takes the following sender and seal:

 

fuel sender = 62161354267; fuel sender seal = 62168782015

 

That said, the sender is probably no longer available new. Are you certain yours has failed?

 

Here’s a thread on repairing fuel senders (I didn’t find Barrett’s article, perhaps he can link it):

 

 

There are some NOS examples still around, but finding one might not be a quick solution.

 

Regards

 

Steve

 

 

[Billsmith]

Steve,

 

Thanks so much for your help.  Looks like Maximillian has that part number available.  Now to troubleshoot and make sure I need it.  I wanted to have it on hand when I pulled the old one out just in case I destroy the old one removing it.

 

One last question.  Unfortunately, I let it run out of gas thinking I had a 200 mile range.  I carry a two gallon gas can around with me.  When I refilled it, it only took 10 gallons to fill it up.  Not sure what is going on with that.  I thought I was on level ground and worked hard to feed all the gas in that the tank would take?

 

Bill

[Conserv]

1 hour ago, Billsmith said:

Steve,

 

Thanks so much for your help.  Looks like Maximillian has that part number available.  Now to troubleshoot and make sure I need it.  I wanted to have it on hand when I pulled the old one out just in case I destroy the old one removing it.

 

One last question.  Unfortunately, I let it run out of gas thinking I had a 200 mile range.  I carry a two gallon gas can around with me.  When I refilled it, it only took 10 gallons to fill it up.  Not sure what is going on with that.  I thought I was on level ground and worked hard to feed all the gas in that the tank would take?

 

Bill

I don’t know, Bill. The fuel pickup may not drain the tank dry. You might have a dent in the underside of the tank. Yes, they theoretically hold 12-ish gallons. But who knows? I believe on some of my largest fill-ups — these occurred before gas pumps had automatic shut-offs — I was partially filling the filler neck!

 

The appearance of a part number and price on the Mobile Tradition parts listing does not guarantee availability. Just saying... ?

 

Regards,

 

Steve

 

[BarrettN]

Here's a link to my writeup on rebuilding sending units - https://www.bmw2002faq.com/forums/topic/237622-fuel-tank-sending-unit-now-rebuilt/

 

 

Edited March 2, 2021 by BarrettN

[Billsmith]

When I disconnect the two wires from the sending unit and turn the switch on, the gauge reads empty.  With the wires connected, it shows full.  What is this telling me?

[BarrettN]

The best way in my opinion to troubleshoot the sending unit is to understand how it works. When the tank is full the float rides high in the tube, and the resistance is less because the float bridges between the resistance wire at its shortest length. When the tank is empty and the float is at the bottom, the electricity has to go down the length of the resistance wire down to where the float is at, resulting in a higher resistance. Just taking the resistance of the sending unit resistance into account, it's closest to zero resistance when the float us at the top, when it's at the bottom its 75+ ohms. 

 

Now compare your results - with the wires disconnected (where - the gauge or at the sender?) an open circuit is infinite resistance - which behaves like empty, because infinite is greater than the 75 or more ohms of resistance needed for the gauge to read empty. (I'll bet if you check the needle is buried at the limit). 

 

With the wires connected it is  acting as if there's no resistance (that's what you expect if the tank is full) - if its not full it could be that the float inside the sending unit is stuck up high, or maybe the wires to the sending unit are shorted out against each other. 

Edited March 3, 2021 by BarrettN

[Billsmith]

Barrett and Steve,  Thanks so much for the simple explanations and for taking the time to provide them.  Very helpful.  Bill

[PeterCS]

I have this sender which I am told is for a tii -never used.

Peter

 

[Son of Marty]

It may fit the Tii tank but the Tii unit doesn't have the fuel pick up and return built into the level sender.