Fuel Sender for 1994 K-series Caterham 7
Discussion
Hello
I need to replace the fuel sender from a 1994 K-series Caterham 7, but it's proving frustratingly difficult tracking down the source of this part - given the age of the car and the fact that it has a K-series engine, I suspect the sender may be from an MG-Rover vehicle, but if so, I've been unable to identify which.
Some details of the old unit as removed from the tank, as follows.
Critical Dimensions (nominal and approximate):
Mounting flange bolt pattern: 6 off Ø5mm holes on a 60mm PCD (maybe 2.375” PCD)
Float arm length: 120mm
Vertical distance of float arm pivot below mounting flange: 115mm
Markings on Rheostat Housing:
7 30 33
824 / 10 / 4
11 93 38 / 5 26
Can anyone identify this part? If not, is there a good, compatible alternative?
I need to replace the fuel sender from a 1994 K-series Caterham 7, but it's proving frustratingly difficult tracking down the source of this part - given the age of the car and the fact that it has a K-series engine, I suspect the sender may be from an MG-Rover vehicle, but if so, I've been unable to identify which.
Some details of the old unit as removed from the tank, as follows.
Critical Dimensions (nominal and approximate):
Mounting flange bolt pattern: 6 off Ø5mm holes on a 60mm PCD (maybe 2.375” PCD)
Float arm length: 120mm
Vertical distance of float arm pivot below mounting flange: 115mm
Markings on Rheostat Housing:
7 30 33
824 / 10 / 4
11 93 38 / 5 26
Can anyone identify this part? If not, is there a good, compatible alternative?
Thanks for the swift response, but I'm okay for a pump (I managed to track down a complete "New-Old-Stock" pump assembly from Rob at Boss Racing).
It's the fuel sender unit I need - It sits in the top of the tank and consists of a float-operated lever arm, operating on a rheostat, such that resistance measured is proportional to fuel level. As I mentioned in my original post, its probably a standard part from an MG-Rover, but I can't trace which.
It's the fuel sender unit I need - It sits in the top of the tank and consists of a float-operated lever arm, operating on a rheostat, such that resistance measured is proportional to fuel level. As I mentioned in my original post, its probably a standard part from an MG-Rover, but I can't trace which.
Laurence7 said:
Hello
Critical Dimensions (nominal and approximate):
Mounting flange bolt pattern: 6 off Ø5mm holes on a 60mm PCD (maybe 2.375” PCD) that's the same
Float arm length: 120mm it can be made this long (short)
Vertical distance of float arm pivot below mounting flange: 115mm not sure about this. Do you mean with the arm at full droop this is the vertical drop from the flange to the centre of the float?
This is like the generic one I have: https://www.moss-europe.co.uk/fuel-sender-tb9006ki...Critical Dimensions (nominal and approximate):
Mounting flange bolt pattern: 6 off Ø5mm holes on a 60mm PCD (maybe 2.375” PCD) that's the same
Float arm length: 120mm it can be made this long (short)
Vertical distance of float arm pivot below mounting flange: 115mm not sure about this. Do you mean with the arm at full droop this is the vertical drop from the flange to the centre of the float?
Hello Bert!
Yes, I plead guilty to being “Laurence of Clubsport fame”, though I think “fame” might be overstretching it a bit!
It was my involvement first in Formula Ford and then in 750MC Bikesports with the Radical Clubsport that led to my little Caterham falling into neglect. It’s been stored under a car cover in a dry garage unloved for the best part of two decades, but has now become the subject of efforts to bring it back to life, get it through an MOT and then back on track (just for track days - not racing).
Despite the passing years, it’s mostly faired pretty well in hibernation – with the exception of the inside of the fuel tank, the pump and sender unit being caked in corruption and corrosion! I’ve given the tank a good soapy high-pressure jet washing and have managed to source a new pump assembly, but am stuck for a fuel sender unit – hence my cry for help.
Regarding the fuel sender unit and to clarify my description of “Vertical distance of float arm pivot below mounting flange: 115mm”, the float arm pivots at a point low down on what I’ve called the “rheostat housing”, which is basically a sheet-metal box (housing the rheostat), spot welded to the strut that projects down from the mounting flange. This point, about which the arm pivots, is about 115mm below the bottom face of the mounting flange. The float arm will then sit at a fairly shallow angle (about 20deg), with the float sitting on the floor of the tank when empty.
Hopefully this will make a bit more sense (perhaps?), but if not, I’ll try to upload some pictures.
Yes, I plead guilty to being “Laurence of Clubsport fame”, though I think “fame” might be overstretching it a bit!
It was my involvement first in Formula Ford and then in 750MC Bikesports with the Radical Clubsport that led to my little Caterham falling into neglect. It’s been stored under a car cover in a dry garage unloved for the best part of two decades, but has now become the subject of efforts to bring it back to life, get it through an MOT and then back on track (just for track days - not racing).
Despite the passing years, it’s mostly faired pretty well in hibernation – with the exception of the inside of the fuel tank, the pump and sender unit being caked in corruption and corrosion! I’ve given the tank a good soapy high-pressure jet washing and have managed to source a new pump assembly, but am stuck for a fuel sender unit – hence my cry for help.
Regarding the fuel sender unit and to clarify my description of “Vertical distance of float arm pivot below mounting flange: 115mm”, the float arm pivots at a point low down on what I’ve called the “rheostat housing”, which is basically a sheet-metal box (housing the rheostat), spot welded to the strut that projects down from the mounting flange. This point, about which the arm pivots, is about 115mm below the bottom face of the mounting flange. The float arm will then sit at a fairly shallow angle (about 20deg), with the float sitting on the floor of the tank when empty.
Hopefully this will make a bit more sense (perhaps?), but if not, I’ll try to upload some pictures.
So, I've just registered as a PostImage user (for free uploads), and if (big if!), I've successfully uploaded some pictures of the fuel sender unit, you should see them here
https://i.postimg.cc/Kjb4TM0d/IMG-5448-Fuel-Sender...
https://i.postimg.cc/GhcHhv8D/IMG-5451-Fuel-Sender...
https://i.postimg.cc/Kjb4TM0d/IMG-5448-Fuel-Sender...
https://i.postimg.cc/GhcHhv8D/IMG-5451-Fuel-Sender...
Yes that makes sense and I've not seen one like that. All the the senders I've looked at have the box attached to the top plate.
Id contact Chris at Redline and see what he can do.
Depending on the baffles in the tank you may have enough width to use the one I posted a link to if all else fails.
Id contact Chris at Redline and see what he can do.
Depending on the baffles in the tank you may have enough width to use the one I posted a link to if all else fails.
Thanks for further inputs Bert. I tried Chris at Redline today without success - I’ll try again in the new year (the interlude between Christmas and New Year is never a good time to be in too much of a rush to get parts).
In the meantime, the plot thickens (this is becoming one of those learning exercises where the more you learn, the less you seem to know).
Merlin Motorsport market a Racetech Fuel Level Sender https://www.merlinmotorsport.co.uk/p/racetech-fuel...
It has the correct mounting plate bolt pattern and has both a very long float arm and very long vertical ‘stalk’: I assume that both (arm and stalk) can be cut to length to suit – important for the Caterham tank since it is relatively shallow, short from front to back, and, in the case of the S3 Rover/Vauxhall tank, narrow between the baffles, so sender dimensions and orientation within the available space are important.
The Merlin advert blurb states “Sender reads Zero Ohms at empty and 183 Ohms at full”, but (and here’s where the plot thickens), I’ve noticed that some gauges and senders are designed to show EMPTY at minimum resistance, while others to show FULL at minimum resistance.
So, the question arises, does the Caterham fuel gauge register EMPTY or FULL with the sender at minimum resistance?
Another option might be to source a VDO 'dip tube' type sender, but I haven't been able to track one down short enough (it would need to be about 180mm tall), with the right attachment flange bolt pattern.
In the meantime, the plot thickens (this is becoming one of those learning exercises where the more you learn, the less you seem to know).
Merlin Motorsport market a Racetech Fuel Level Sender https://www.merlinmotorsport.co.uk/p/racetech-fuel...
It has the correct mounting plate bolt pattern and has both a very long float arm and very long vertical ‘stalk’: I assume that both (arm and stalk) can be cut to length to suit – important for the Caterham tank since it is relatively shallow, short from front to back, and, in the case of the S3 Rover/Vauxhall tank, narrow between the baffles, so sender dimensions and orientation within the available space are important.
The Merlin advert blurb states “Sender reads Zero Ohms at empty and 183 Ohms at full”, but (and here’s where the plot thickens), I’ve noticed that some gauges and senders are designed to show EMPTY at minimum resistance, while others to show FULL at minimum resistance.
So, the question arises, does the Caterham fuel gauge register EMPTY or FULL with the sender at minimum resistance?
Another option might be to source a VDO 'dip tube' type sender, but I haven't been able to track one down short enough (it would need to be about 180mm tall), with the right attachment flange bolt pattern.
Interesting. I spent some time yesterday trying to get my new sender to fit my new tank (standard S3 carbs version). With the baffles you actually have very little width for the arm. Also you can't see in the tank to get the right length arm.
So on recommendation of blatchat I made a model out of foam board. I had to bend the arm to get the float forward and you don't get enough length for it to get to the bottom of the tank. It'll do, but I think it'll read empty with quite a lot of fuel actually left in it. I'll be able to test how much fuel takes it from empty when it's all properly fitted
Being able to position the arm pivot point half way down seems a good idea provided it goes above centre as well as below.
So on recommendation of blatchat I made a model out of foam board. I had to bend the arm to get the float forward and you don't get enough length for it to get to the bottom of the tank. It'll do, but I think it'll read empty with quite a lot of fuel actually left in it. I'll be able to test how much fuel takes it from empty when it's all properly fitted
Being able to position the arm pivot point half way down seems a good idea provided it goes above centre as well as below.
Laurence7 said:
The Merlin advert blurb states “Sender reads Zero Ohms at empty and 183 Ohms at full”, but (and here’s where the plot thickens), I’ve noticed that some gauges and senders are designed to show EMPTY at minimum resistance, while others to show FULL at minimum resistance.
So, the question arises, does the Caterham fuel gauge register EMPTY or FULL with the sender at minimum resistance?
This is easy to test: with the ignition on, connect the sender feed wire to the fuel gauge to ground (this is the same as reading zero ohms). Then check the gauge to see if it is at full scale (full) or reading empty. So, the question arises, does the Caterham fuel gauge register EMPTY or FULL with the sender at minimum resistance?
Thanks Jeremy - As you say, an easy test, so why didn’t I think of it ?!
So if, when grounded, the feed wire produces an EMPTY signal at the gauge, does that mean (and forgive my ignorance of electrickery here), that when the feed wire is disconnected and therefore open circuit, resulting in infinite resistance, the gauge will show FULL?
So if, when grounded, the feed wire produces an EMPTY signal at the gauge, does that mean (and forgive my ignorance of electrickery here), that when the feed wire is disconnected and therefore open circuit, resulting in infinite resistance, the gauge will show FULL?
Laurence7 said:
Thanks Jeremy - As you say, an easy test, so why didn’t I think of it ?!
So if, when grounded, the feed wire produces an EMPTY signal at the gauge, does that mean (and forgive my ignorance of electrickery here), that when the feed wire is disconnected and therefore open circuit, resulting in infinite resistance, the gauge will show FULL?
No probably not, because the gauge will need some current flowing through it to move the needle mechanism.So if, when grounded, the feed wire produces an EMPTY signal at the gauge, does that mean (and forgive my ignorance of electrickery here), that when the feed wire is disconnected and therefore open circuit, resulting in infinite resistance, the gauge will show FULL?
An open circuit won't allow any current to flow, whereas your fuel sender even at it's highest resistance will allow enough current to flow through the gauge to move the needle.
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