Author Topic: Fuel level sending unit question  (Read 7250 times)

Offline guitbiking

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Fuel level sending unit question
« on: November 30, 2019, 04:19:29 PM »
I have a fuel level sending unit that has wires broken off at the connectors at the base of the unit inside of the tank. I'm not concerned with losing the fuel level function (can use odometer like other bikes). But, I need to power the fuel pump. The ground wire is still intact, but the power to the fuel pump wire is not only broken off, but there is no nib to solder it to.
 It would seem that the base plate could be drilled such that the two fuel pump wires could be routed through it using a fuel safe grommet and sealer. Much like the little plastic original connector accomplishes.
I'm thinking other applications of in-tank fuel pumps must accomplish getting the wires to it in a similar fashion, without including a 200 dollar fuel level attachment :(
Before I do an lengthy search, has anybody done this type of repair? Thanks!
  • Western PA
  • 85 K100RT; 87 K100RT; 90 K75RT

Offline Laitch

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Re: Fuel level sending unit question
« Reply #1 on: November 30, 2019, 05:13:13 PM »
Before I do an lengthy search, has anybody done this type of repair?
Somebody must have done it to have created a market for fuel-tight grommets. Give it a go and show others a path out of this condition.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline guitbiking

  • Curious
  • Posts: 6
Re: Fuel level sending unit question
« Reply #2 on: December 01, 2019, 10:57:30 AM »
I came up with this item that might fit the bill. https://www.summitracing.com/parts/abt-cfd-504/overview/. Usually for the top of a fuel cell. But I was thinking of running PTFE insulated wires through it and putting a little JB Weld Steel Stik on the connector for good measure.

The other option would be to run a bulkhead stud through. Then connect wires to the outside and the inside of the stud. Probably only one for + and use the existing ground post on the sending unit plate. As I doubt there is room for two studs in the plate without weakening it.

Any thoughts on the legitimacy of my thinking? It would be about a 50 dollar fix.
  • Western PA
  • 85 K100RT; 87 K100RT; 90 K75RT

Offline volador

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Re: Fuel level sending unit question
« Reply #3 on: December 01, 2019, 11:17:42 AM »
I came up with this item that might fit the bill. https://www.summitracing.com/parts/abt-cfd-504/overview/. Usually for the top of a fuel cell. But I was thinking of running PTFE insulated wires through it and putting a little JB Weld Steel Stik on the connector for good measure.

The other option would be to run a bulkhead stud through. Then connect wires to the outside and the inside of the stud. Probably only one for + and use the existing ground post on the sending unit plate. As I doubt there is room for two studs in the plate without weakening it.

Any thoughts on the legitimacy of my thinking? It would be about a 50 dollar fix.

BADA BOOM
pm sent
  • NYC NY
  • 1991 K100RS 1993 K75S ABS
5 BOROUGHS SISYPHEAN SOCIETY  MAINTAINING THE OBSESSION

Offline guitbiking

  • Curious
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  • Western PA
  • 85 K100RT; 87 K100RT; 90 K75RT

Offline Laitch

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Re: Fuel level sending unit question
« Reply #5 on: December 01, 2019, 12:26:25 PM »
Any thoughts on the legitimacy of my thinking? It would be about a 50 dollar fix.
Your thinking seems reasonably dispassionate and analytical. There's always this, too. It would likely give you a pump connection you could strengthen; function of the fuel level sender would still be questionable.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline guitbiking

  • Curious
  • Posts: 6
Re: Fuel level sending unit question
« Reply #6 on: December 08, 2019, 05:10:04 PM »
All for naught. I was able to melt the plastic around the post enough to solder a wire to it. I was also able to clamp the wire so that there is no tension on the solder.
Happy trails to you.
  • Western PA
  • 85 K100RT; 87 K100RT; 90 K75RT

Offline Laitch

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Re: Fuel level sending unit question
« Reply #7 on: December 08, 2019, 06:57:33 PM »
All for naught.
Which was the all and which was the naught.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline The Mighty Gryphon

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Re: Fuel level sending unit question
« Reply #8 on: December 08, 2019, 07:22:15 PM »
So you're telling us your repair didn't work?
  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline Chaos

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Re: Fuel level sending unit question
« Reply #9 on: December 09, 2019, 01:09:33 AM »
No, I think he's saying posting here was an exercise in futility.
  • sw ohio
1987 K75S    VIN 0231
Original owner, Original litter
200,000 miles (plus or minus) and 5 paint jobs
sold 6/23
2023 Ural 2WD sidecar (BMW's bastard step child)

Offline Laitch

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Re: Fuel level sending unit question
« Reply #10 on: December 09, 2019, 09:48:25 AM »
I think he's saying posting here was an exercise in futility.
Probably. I think his innate genius will carry the day wherever he goes.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline guitbiking

  • Curious
  • Posts: 6
Re: Fuel level sending unit question
« Reply #11 on: December 09, 2019, 10:20:35 AM »
Holy crap! I just meant that I was able to melt the plastic on the original part such that I could attach the wires and solve the problem without having to do a work around as I thought was my only option. I reached out for help and was encouraged to try it.
 Perhaps a poor choice of wording on my part in the follow-up, by trying to be brief. But did it really seem that I was being arrogant or offensive?
I don't often ask questions, because I do extensive research on this and several other sites before asking. I am grateful for all of the helpful information.
  • Western PA
  • 85 K100RT; 87 K100RT; 90 K75RT

Offline Scott

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Re: Fuel level sending unit question
« Reply #12 on: December 09, 2019, 10:37:55 AM »
Holy crap! I just meant that I was able to melt the plastic on the original part such that I could attach the wires and solve the problem without having to do a work around as I thought was my only option. I reached out for help and was encouraged to try it.
 Perhaps a poor choice of wording on my part in the follow-up, by trying to be brief. But did it really seem that I was being arrogant or offensive?
I don't often ask questions, because I do extensive research on this and several other sites before asking. I am grateful for all of the helpful information.
I understood what you did and you also were able to take the strain off the repaired joint as well. Good job in this throw away and buy new culture.
  • SoCal
  • bmw R100r, bmw k75, hondapotamus G/W, XT 500 enduro

Offline The Mighty Gryphon

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Re: Fuel level sending unit question
« Reply #13 on: December 09, 2019, 11:32:08 AM »
Your wording led me to think the repair wasn't ultimately successful.  Very glad to hear it worked well. 

Is it possible to post a photo of what you did?  I have a tank connector with a similar issue and would like to try your repair.
  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline guitbiking

  • Curious
  • Posts: 6
Re: Fuel level sending unit question
« Reply #14 on: December 09, 2019, 12:42:32 PM »
It is under a gasoline filled tank at this point. I will try to illustrate with a found photo. [img]
* fuel sender fix.jpg (43.97 kB . 544x576 - viewed 555 times)[img].
The metal post continues down into the plastic nib, the green line. (Actually it is the wire on the backside, but looks the same.)
I melted the nib with the solder iron until I had enough metal showing to solder to. I then ran the wire through the old float mechanism and pinched the wire with the tab, red line.
A bit of a hack, but it did the job.
  • Western PA
  • 85 K100RT; 87 K100RT; 90 K75RT

Offline Laitch

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Re: Fuel level sending unit question
« Reply #15 on: December 09, 2019, 12:48:31 PM »
Thanks for the illustration.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline Scott

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Re: Fuel level sending unit question
« Reply #16 on: December 09, 2019, 12:53:22 PM »
I did the same sort of thing on my xt500d, about five years ago on the rectifier diode, I guess it's fixed.

  • SoCal
  • bmw R100r, bmw k75, hondapotamus G/W, XT 500 enduro

Offline The Mighty Gryphon

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Re: Fuel level sending unit question
« Reply #17 on: December 09, 2019, 01:16:13 PM »
Nice job!
  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline Chaos

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  • Mars needs women!
Re: Fuel level sending unit question
« Reply #18 on: December 09, 2019, 01:39:41 PM »
Holy crap! I just meant that I was able to melt the plastic on the original part such that I could attach the wires and solve the problem without having to do a work around as I thought was my only option. I reached out for help and was encouraged to try it.
 Perhaps a poor choice of wording on my part in the follow-up, by trying to be brief. But did it really seem that I was being arrogant or offensive?
I don't often ask questions, because I do extensive research on this and several other sites before asking. I am grateful for all of the helpful information.

Don't take it personally. If we're not out riding we're sitting around making obtuse remarks online.  Glad you got your dilemma fixed!
  • sw ohio
1987 K75S    VIN 0231
Original owner, Original litter
200,000 miles (plus or minus) and 5 paint jobs
sold 6/23
2023 Ural 2WD sidecar (BMW's bastard step child)

Offline Past-my-Prime

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  • All of us are better when we're loved.
Re: Fuel level sending unit question
« Reply #19 on: December 10, 2019, 09:39:58 PM »
Hey I understood "All for Naught"!

It means "All the drama for no big deal" which implies that after the help, you were able to find your way through.

Good job mate!
  • North Shore of Lake Superior (in my garage)
  • BRICK: 1989 K75 RT - Rocinante; NON-BRICK: 2007 F650 GS Dakar - Betty Blue

Offline volador

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Re: Fuel level sending unit question
« Reply #20 on: December 12, 2019, 07:11:32 PM »
Hey I understood "All for Naught"!

It means "All the drama for no big deal" which implies that after the help, you were able to find your way through.

Good job mate!
Surprisingly you did not mention "splines"
  • NYC NY
  • 1991 K100RS 1993 K75S ABS
5 BOROUGHS SISYPHEAN SOCIETY  MAINTAINING THE OBSESSION

Offline Past-my-Prime

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  • All of us are better when we're loved.
Re: Fuel level sending unit question
« Reply #21 on: December 13, 2019, 10:25:08 PM »
"splines splines everywhere the splines,
do this don't do that"

Sorry, back to your usual programming. I've been into the rum and eggnog this chilly evening.
  • North Shore of Lake Superior (in my garage)
  • BRICK: 1989 K75 RT - Rocinante; NON-BRICK: 2007 F650 GS Dakar - Betty Blue

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