M535i (B34) In-Tank Fuel Sender Unit

E28 technical advice asked and given! Troubleshooting, modifications and more.
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Alan
Posts: 9
Joined: Aug 20, 2019 4:10 PM
Location: Dublin

M535i (B34) In-Tank Fuel Sender Unit

Post by Alan »

Hi All.

Might any of you knowledgeable folks have a workaround/fix for the fuel sender unit? I can confirm the problem lies with the sender unit. Shorting the pins onbthe cable going to the sender unit gives me fully empty and fully full.

I looked inside the sender unit. Hopefully I didn't break it. I don't recall seeing the two small wires extending through the full length of the internals. I'll double check this today though.

The obvious thing is to simply replace with a new unit, but these are not cheap. In EU they're 300 euros or so, and inbthe states, they're cheaper, but then I have the taxes and delivery costs , bringing up the proce again.

If there's a repair I'm then I'd love to try that, or if any of you have a confirmed good second hand one then I could maybe go for that.

Thanks in advance.

On a side note, I have resurrected my M535i after 18 years of storage and ownership. All the correct re-torqueing and re-lubing, and lots of other things have been done. She starts and drives as it should - and it's great fun!!!!
Alan
Posts: 9
Joined: Aug 20, 2019 4:10 PM
Location: Dublin

Re: M535i (B34) In-Tank Fuel Sender Unit

Post by Alan »

Also, to point out, this sender unit literally worked only days ago!! I took it out to replace the in-tank pump. Hasn't worked since.
ccchrisss
Posts: 39
Joined: Aug 02, 2023 2:46 PM
Location: Irvine, CA

Re: M535i (B34) In-Tank Fuel Sender Unit

Post by ccchrisss »

Congrats on the resurrection! I have no info on how to repair the sending unit, but I did replace mine with a cheap copy (herko unit) and it's been working fine for over a year. Might be a little hard to find now but they should be around 60-80 euros, a cheaper option if you want to go that route.
JohnH
Posts: 699
Joined: Jan 24, 2007 9:55 AM
Location: Surrey,UK

Re: M535i (B34) In-Tank Fuel Sender Unit

Post by JohnH »

Quite a simple fix to rewire it with Cr20Ni80 0.08mm wire. Just needs soldering, nothing clever. Available on ebay for a few Euros.
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