Fuel sender unit, ceramic resistor availability?

[Kiwipom]

Hi, I fitted an aftermarket fuel sender resistor (see pic) in an attempt to avoid buying a complete BMW pump unit, but it cracked apart, just last the original, only after a month.

I can’t find the same resistor part on ebay, which is where I bought it before. I was going to get another and try to glue it place to stop it flexing and cracking.

Is the only option a new (or used) BMW unit or is there another source of the resistor part, or another fix method?

I did notice chinese pump assemblies are available on ebay (see pic) are these worth a try?

 

[bonbon]

Search the net - there was a chap in Holland who printed some ceramic plates.

 

[Kiwipom]

Search the net - there was a chap in Holland who printed some ceramic plates.

The pic in my post above is of the plate I bought from the chap in holland in 2020, lasted no time at al, but in any event I have so far found no sign of them being sold on ebay, or the wider web. Which maybe is not surprising if complete units are now available cheaply.
It looks like I will have to take a chance with the oem copy, if no one on here has yet tried one, I wonder if it uses the same design if resistor.

 

[Kiwipom]

I am waiting for this pump assembly including sender to arrive. I will

investigate swapping the pump from my oem unit into it before fitting…

 

[bonbon]

The pic in my post above is of the plate I bought from the chap in holland in 2020, lasted no time at al, but in any event I have so far found no sign of them being sold on ebay, or the wider web. Which maybe is not surprising if complete units are now available cheaply.
It looks like I will have to take a chance with the oem copy, if no one on here has yet tried one, I wonder if it uses the same design if resistor.

What do you mean it lasted no time? How did it fail?

 

[Kiwipom]

What do you mean it lasted no time? How did it fail?

It cracked into pieces after a weeks or two gauge went back to zero with orange light as before, I suspect the float arm was either too loose on its pivot (age related issue), or maybe I’m getting a vacuum in the tank and the tank wall is bending the float arm, or the ceramic is a bit weak….. dunno. I spent ages making sure the float arm was not touching the tank wall before finishing the install.

 

[Mazza]

If you get stuck I have a surplus tank which I could remove the Fuel pump/sender unit assy from

 

[bonbon]

It cracked into pieces after a weeks or two gauge went back to zero with orange light as before, I suspect the float arm was either too loose on its pivot (age related issue), or maybe I’m getting a vacuum in the tank and the tank wall is bending the float arm, or the ceramic is a bit weak….. dunno. I spent ages making sure the float arm was not touching the tank wall before finishing the install.

I had failures with both mechanisms you describe (aside from the ceramic pcb).
Solved the loose arm by inserting a piece of aluminum foil around the pivot arm.
For a few years I solved the vac by a vented Mini cap from a Turkish manufacturer. That cap eventually started to leak - and their new one-way valve design leaks on our cars (not sure why).s So now I don’t empty the tank to zero….

 

[Kiwipom]

If you get stuck I have a surplus tank which I could remove the Fuel pump/sender unit assy from

Thanks, I will report on the chinese unit when I get it, hopefully in a couple of weeks, its very hit or miss in my experience with aliexpress car parts, but if it goes pear shaped and you use paypal refunds are generally easy to get.

I have the resistance figures for the sender from this forum, and did a test myself by putting a 100 ohm resistor in the circuit to see where the gauge moved to, about a third full in my case.

 

[Kiwipom]

I had failures with both mechanisms you describe (aside from the ceramic pcb).
Solved the loose arm by inserting a piece of aluminum foil around the pivot arm.
For a few years I solved the vac by a vented Mini cap from a Turkish manufacturer. That cap eventually started to leak - and their new one-way valve design leaks on our cars (not sure why).s So now I don’t empty the tank to zero….

When I get the new part I will do a careful compare, in the meantime I will also try to find out how the charcoal cannister and valve thing vent the tank, to make sure its not subject to a vacuum BEFORE i fit a new part. Not sure how to test that system yet.
Urban myth says dont fill these cars right up as it stuffs the sender, and chang8ng fuel typevcan “clean” the ceramic resistor etcI wonder how much of that is actually that the cannister gets stuffed by over filling…..I’m prob on the wrong track but ……

 

[bonbon]

If you can advise how to fix the vent I’d be most grateful - in the summer heat here the vac collapses the tank. I already had a failed float arm (with scratches evident on the inside back of the fuel tank).

 

[bonbon]

When I get the new part I will do a careful compare, in the meantime I will also try to find out how the charcoal cannister and valve thing vent the tank, to make sure its not subject to a vacuum BEFORE i fit a new part. Not sure how to test that system yet.
Urban myth says dont fill these cars right up as it stuffs the sender, and chang8ng fuel typevcan “clean” the ceramic resistor etcI wonder how much of that is actually that the cannister gets stuffed by over filling…..I’m prob on the wrong track but ……

I used 98 octane once a year together with a can of BG44K to clean the ceramic PCB and contacts.

 

[Kiwipom]

Well the pump has been delivered but is faulty so I have asked for a refund or be sent another one. The fuel filter section is loose and not properly fixed to the pump. I have not checked anything else, or looked into fixing it.
See vid on this link

New video by Simon Byrne

photos.app.goo.gl

 

[bonbon]

It’s not clear from your clip what exactly is the problem with the filter

 

[Kiwipom]

It’s not clear from your clip what exactly is the problem with the filter

the filter section should not move freely like in the vid, it should be firmly attached to the bottom of the pump maybe glued I’m not sure…when it is moved a gap (between the pump and filter) appears that means fuel can pass through into the pump inlet, without passing through the filter. On the oem pump the filter is fixed at 90 deg to the main pump body.

A second fault is that one of the anti vibration rubbers is missing….

 

[bonbon]

the filter section should not move freely like in the vid, it should be firmly attached to the bottom of the pump maybe glued I’m not sure…when it is moved a gap (between the pump and filter) appears that means fuel can pass through into the pump inlet, without passing through the filter. On the oem pump the filter is fixed at 90 deg to the main pump body.

A second fault is that one of the anti vibration rubbers is missing….

I have the same Chinese aftermarket part sitting on a shelf. The filter on mine is also a bit flexible as there is a fitting that is molded around the mesh. Are you sure that there is an air opening that can bypass that flexible fitting?
(Mine has both black shock absorbers)

 

[Kiwipom]

I have the same Chinese aftermarket part sitting on a shelf. The filter on mine is also a bit flexible as there is a fitting that is molded around the mesh. Are you sure that there is an air opening that can bypass that flexible fitting?
(Mine has both black shock absorbers)

Yep there was definitely a way the fuel could bypass the filter HOWEVER I was able to unclip the lower part of the pump housing (on what I assume is an oem pump this is all one piece) and this revealed a black “pin” which the filter should be pushed over but wasn’t and so this was the fault, it had not been properly assembled, there is a black moulded rubber “spacer” as well to put back correctly which fits between the pump and housing that helps hold the filter in place, before clipping back the housing.

Luckily one of the anti vibe rubbers on the oem pump can be transferred to the chinese one.

I will check the filter has no other possible leak paths like yours, and continue to check it over before deciding if I fit it complete or make up a pump assembly out of the two of them. The sender section (including pivot bearing) looks like it could be swapped over for example but would involve soldering.

I asked for and got a partial refund from Aliexpress before I took the chinese pump apart in case it broke in the process and they wanted me to return it as a condition of getting a refund (but they didn’t ask).

More pics will follow which will make things clearer.

 

[Kiwipom]

I have successfully fitted the chinese pump assembly, points of note on the pump are:
The fuel filter was incorrectly fitted
The brass resistor contacts were incorrectly fitted
The float/wire could not be used as it pressed the contacts onto the ceramic resistor too well causing the float arm to be too stiff to float

Other notes from memory
The seat can be unbolted and just slid forward rather than removed and wires disconnected
The pump will switch off after a few secs if used to drain the tank so needs an independent power supply to do that
If a plastic tube is pushed through the filler cap it can be used to pull string back up attached to the float for testing purposes
A small cable tie on the float atm allows string to be pulled through it after testing rather than removing the pump again
Resistance of the sender is 20 ohms empty over 150 ohms full and the ohm meter will interfere with the fuel gauge reading if left in the circuit (it passes current through the sender hence also the module controlling the gauge)
There is some smart logic to the sender module as it samples sender resistances and will maintain a fuel gauge reading even when the sender is disconnected
The sender casing and float wire rubbed on the rear tank wall, float was bent to fix this and a heated 4” nail used to melt the sender plastic in key areas to give clearance

 

[Kiwipom]

Vid shows me pulling the string to pull the float up inside the tank….pic shows how I worked out which bits of the swivelling sender unit to remove by melting, and how to bend the float wire.

New video by Simon Byrne

photos.app.goo.gl

 

[bonbon]

The rubbing on the back is due to collapse of the tank due to vacuum when running the tank to empty (as the vac release mechanism on all our cars fails).