How to test the Fuel Sender inside the fuel tank ?

[Dicky&Dawn]

Hello Bongonauts - can any of you shed some light on testing the fuel sender inside the fuel tank or replacing it with another one ?

My fuel gauge went on the fritz a few months back and now I need to fix it before we go Bongoing again this Easter.

At first I followed all the other postings relating to the duff earth connection but that didn't fix the problem. I also tested shorting out the connection back to the fuel gauge to see if the wiring to the gauge and the gauge itself were working ok. So far so good but still the gauge wouldn't work when connected to the sender unit.

I then handed my van into my local garage to investigate the problem and all they did was short out the terminal block and tell me it'll cost £225 for a new sender unit and housing - argh !!!!!

So I then tried the following:-

Removed the cover on the tank and inspected the float and arm was working ok. Connected a multimeter from the black wire at the top of the plastic sender housing up to the connector on the main terminal block where the fuel gauge connects to. This confirmed a connection existed from one end to the other but I couldn't get my meter to show any difference in the reading if I moved the float up and down.

My guess is the sender is bust but I'm louthed to pay £225 if the sender unit can be swapped with another one. The unit itself has a single bolt holding it onto a vertical leg which points down into the tank. Then a wire connects the variable resistor on the plastic sender housing up to the base of the tank cover. So it looks like this is an item which can be replaced independently of the whole unit.

If anyone has any ideas on how to replace the sender unit with another I'd appreciate your advice.

Cheers

Rich

[Bollicky]

hi, yeah i am in the same boat and have been looking for a duff one to play with but no luck yet. As I have a duff one in the tank I shall soon remove it and try a repair,been holding off though hoping to hear from someone who may already have had a go.£225!! scarey my ol Landy 110 was a tenner.

[patmckenna]

Hi Dicky&Dawn
Have sent you a PM.
Pat

[Peg leg Pete]

I just gave the connection a wiggle and the next day the guage worked again

[Richard D]

If anyone has any pictures of the sender I could take them to my mates yard and do some looking.

[alphabetter]

If anyone has any pictures of the sender I could take them to my mates yard and do some looking.

From the parts manual

[Peg leg Pete]

brilliant Alphabetter

[Bollicky]

My fuel indication is now spot on! cost 2 hours most of that head scratching wanna know more?

[pippin]

Nah, not really.

Of course we do!

[Bollicky]

I have been celebrating my success so will give a coherant reply later on

[maxheadroom]

Dicky&Dawn

This is all I have

The F postion is with the float up and E is with the float down.

keep the faith

Bongo Fuel Tank Gauge Unit
Position on the Float
Ohms
F
3±1
1/2
32.5±1
E
110±1
Checkpoints
1. Remove the fuel tank gauge unit.
(refer to sections F1, F2 and F3)
2. When you have removed the float, measure the ohms between the two battery pins.
3. If the ohms are different to those in the table above, or if the ohms do not decrease as you move from point E to point F on the float, the fuel tank gauge unit must be replaced. (Refer to section F1, F2 and F3)

[maxheadroom]

Bollicky can't wait as mine is reading full all the time

keep the faith

[Bollicky]

right then first i tried running an additional earth from the terminal block to the engine so the best there is. Result fuel gauge reading empty indicating an open circuit as if you short the 2 wires going back to the instrument panel you will get a reading of full. stay with me.
I went on after testing the loom wiring yet again as above,to removing the sender unit and took it to the shed for some intimidation.
I cleaned the terminal block spades until they shined and also carefully dissassembled the variable resistor housing and cleaned the contacts with a cotton bud.
After putting it back together I found i got a good reading on my multimeter varying with the movement of the float as you would expect.
Put it all back in the van same reading as before EMPTY!
Took it out again and removed the terminal block by drilling its mounting rivet out .Attatched a wire for ground to the sender/float housing mounting screw and resoldered a new longer wire from the resistor housing.
I then passed the two wires through the small hole left by the origional terminal block and crimped some spade connectors on, then covered the opening with araldite to make a good seal.
A couple of beers later and the araldite is dry enough to return the unit to the vehicle, i had already cut off the origional female connector on the loom so made neat with insulation tape and a cable tie.
Result perfect reading
Looking at the terminal block from the top of the sender assembley that I removed I see that the earthing is made by the plastic sandwiching a metal plate to the metal surface via a rivet,dirt/corrosion and sealiing gunk was evident under this so no way was a descent connection to the other end of the resistor ever going to be made for the blocks spade.
Running out of puff now how many chapters is that. hope it makes sense.
Took some pics too.

[mikeonb4c]

This sounds like a really good piece of work Bollicky - BF Factsheet stuff / Bongoogle if you take some pics and Ian and Ozric are able to oblige.

Mike

[maxheadroom]

Cheers Bollicky,

Tried your top tip today and hey presto my fuel gauge now works.
Thanks to your head scratching only took an hour.

Regards Maxheadroom

Keep the faith