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Fitting 850 6 screw fuel tank sender unit
https://www.ausmini.com/forums/viewtopic.php?f=2&t=95039		 Page 1 of 1
Author:  TartanRed [ Tue Mar 14, 2017 8:26 pm ]
Post subject:  Fitting 850 6 screw fuel tank sender unit
Hi, next question for the experts: I had to swap the dead sender unit in my 850 fuel tank. I had a good working one and have cleaned everything up ready to refit. I lashed out on a new cork gasket. My question is should I used a sealant on the gasket (ie like a Permatex flexible cement) or fit the cork gasket dry. Some interweb research suggests that the cork was meant to work without any sealant, but I have had (admittedly ancient) cork gaskets leak previously.

Matt

PS if anyone has tips on how to pull apart and repair the faulty sender unit, I'm all ears - seems a shame to toss a part that should be fixable with a bit of know-how... :)
Author:  jambos [ Tue Mar 14, 2017 9:19 pm ]
Post subject:  Re: Fitting 850 6 screw fuel tank sender unit
Matt

I will happily buy the old sender off you, pm me what you want for it.

Laurence

TartanRed wrote:
Hi, next question for the experts: I had to swap the dead sender unit in my 850 fuel tank. I had a good working one and have cleaned everything up ready to refit. I lashed out on a new cork gasket. My question is should I used a sealant on the gasket (ie like a Permatex flexible cement) or fit the cork gasket dry. Some interweb research suggests that the cork was meant to work without any sealant, but I have had (admittedly ancient) cork gaskets leak previously.

Matt

PS if anyone has tips on how to pull apart and repair the faulty sender unit, I'm all ears - seems a shame to toss a part that should be fixable with a bit of know-how... :)
Author:  wild_willy [ Wed Mar 15, 2017 7:44 am ]
Post subject:  Re: Fitting 850 6 screw fuel tank sender unit
Most sealants will dissolve when in contact with petrol. The screws have small copper washers to help seal the threads but don't always seal properly the second or third time around. I use Stag Paste to seal threads and under the washer. A new cork seal should be Ok without any sealant.

The sender's resistance wire can be cleaned and the wiping contact slightly re-tensioned to make contact over the full range of contact. Use an ohmmeter to check for continuity over the full range.
Author:  drmini in aust [ Wed Mar 15, 2017 7:50 am ]
Post subject:  Re: Fitting 850 6 screw fuel tank sender unit
Don't use any sort of silicone sealant on the gasket. It dissolves into the petrol then floats around and can clog the strainer, as I found on an outboard tank once.
Author:  mini0998 [ Wed Mar 15, 2017 4:26 pm ]
Post subject:  Re: Fitting 850 6 screw fuel tank sender unit
When I replaced mine I used loctite No 3 on both sides of the cork gasket. Has been in for 5 years or so now without a leak.
Author:  drmini in aust [ Wed Mar 15, 2017 4:35 pm ]
Post subject:  Re: Fitting 850 6 screw fuel tank sender unit
Loctite #3 gasket sealant is fine, it used to be called Permatex #3.
Author:  TartanRed [ Wed Mar 15, 2017 8:08 pm ]
Post subject:  Re: Fitting 850 6 screw fuel tank sender unit
Thanks for all the comments. I have fitted the sender tonight without any sealant on the gasket, just some Loctite on the screw threads. Will see how it goes once the tank has fuel in it again - I have Loctite No.3 if it leaks, and some spare gaskets.

Cheers
Matt
Author:  John Smidt [ Wed Mar 15, 2017 8:16 pm ]
Post subject:  Re: Fitting 850 6 screw fuel tank sender unit
TartanRed wrote:
Hi, next question for the experts: I had to swap the dead sender unit in my 850 fuel tank. I had a good working one and have cleaned everything up ready to refit. I lashed out on a new cork gasket. My question is should I used a sealant on the gasket (ie like a Permatex flexible cement) or fit the cork gasket dry. Some interweb research suggests that the cork was meant to work without any sealant, but I have had (admittedly ancient) cork gaskets leak previously.

Matt

PS if anyone has tips on how to pull apart and repair the faulty sender unit, I'm all ears - seems a shame to toss a part that should be fixable with a bit of know-how... :)


If you want to give me a call tomorrow, I will explain how to fix the old one, if it is not too far gone
02 45776221
Regards

John
Author:  Timbo [ Thu Mar 16, 2017 10:52 am ]
Post subject:  Re: Fitting 850 6 screw fuel tank sender unit
The sender unit in my Traveller was pretty stuffed. The coil had burnt out, but it had got so hot that the former in the middle of it had charred (that can't be a good thing to have happening inside a fuel tank!). I sent it to Roger Howard at Howard Instruments and he replaced the coil and re-plated the body. It came back looking like a new one and should do another 50 or so years.

Tim
Author:  TartanRed [ Sun Mar 19, 2017 6:59 pm ]
Post subject:  Re: Fitting 850 6 screw fuel tank sender unit
Hi John, thanks for your offer - didn't see your post until the weekend. Will give you a ring this week. The sender appears in good condition externally, but is open circuit. I'm hoping it is just a broken wire and easily fixed, but I can't figure out how to open it up. There appears to be a spot weld holding the two halves together. I had assumed they would separate easily after straightening out the three twist lock tangs, but apparently not so...

If the internal coil needs rewinding I will definitely try Rodger Howard.

Cheers
Matt
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