Fuel Guage Sender

Had some trouble with my BMW 325I, turned out it was the fuel pump..and only 160,000 miles. Pulled the pump assembly out and was surprised at the sending unit. Basically an oval shaped tube straight down into the tank about 8" long. The top plate has 4 holes for mounting and a nice weatherpack type socket for the wiring. The tube has no exterior components, and it seems it would operate well in a foam filled tank.
I needed the car so I replaced it, but it looks like a really simple unit that would fit the type of tanks most of us are using. Has anyone out there tried this unit? and is there any info on the resistance value of the sender?
Cheers
Phil
 
Phil,
Fuel Safe makes one similar if not the same. It comes in different resistance values, so you choose which one you want/need. They have several neat features. They come in two lengths, but can be shortened. Easily calibrated and have an accessory feature that can be wired for a low warning light that can be set to any level you want. It is what I am using in mine and I have a light added on my dash just for that function. They also have a gauge to go with it if you want or use your own.

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Bill
 
Bill:
Thanks, I will check it out, since I didn't know the resistance value and I needed the car I re-assembled it without measuring.
Bob, I had seen the Centroid unit but I was a bit put-off by the need for a conversion box that I assumed converted the capacitance value to a voltage output, I may be wrong on that and I will check it out also, thanks for the info. My tanks are baffled, and it just seemed a nice solution to not have a swinging float assembly that was infleuenced by cornering and braking forces etc.
Thanks again
Phil
 
I didn't notice the page marker didn't change when it gave the catalogue selection. Should have clicked on it to get the representative unit. Yes it isn't cheap. for that reason and some others, I chose only one sender, and one gauge. I have a connector hose from the drivers side to the passenger side, with a one way valve in line. Fuel pickup is on the passenger side and return is to the driver's side.

Bill
 
Just thinking about its "method operandi" a bit more.......

Does it operate by having a resistive centre section and a ground outer tube and the liquid shorts across the gap, thereby creating the circuit? The high the fuel rises the less of the resistive element is in the air gap and therefore the lower the resistance of the circuit. By adjusting the minimum and maximum resistive readings, that gives an adjustable (or set-up-able?) fuel sender?

What an incredibly simple, but effective system, if my deductions are correct. Pity it is so expensive though.
 
Bill:
Thanks, I will check it out, since I didn't know the resistance value and I needed the car I re-assembled it without measuring.
Bob, I had seen the Centroid unit but I was a bit put-off by the need for a conversion box that I assumed converted the capacitance value to a voltage output, I may be wrong on that and I will check it out also, thanks for the info. My tanks are baffled, and it just seemed a nice solution to not have a swinging float assembly that was infleuenced by cornering and braking forces etc.
Thanks again
Phil
The Centroid senders that I've used require no intermediate adapter. Their output directly mimics a standard resistance sender.
 
Gents:
Thanks for all the input. I checked out all of the available units mentioned and they all seem to be similar, The BMW unit is actually made by VDO, and is an OEM piece, but they do offer others in various lengths over the counter. The Centroid unit looks like it can be tailored to any length which is a definite plus even though it is a bit pricey, all things considered it may be the way to go. The Fuel safe unit looks good too. I may go for one sender as Bill mentioned, and set up things that way. I didn't want to install something and find a better mousetrap down the road. I guess if it works and is reliable a few bucks more is well spent on getting it right the first time.
Thanks
Phil
 
Unless it is patented?? a resistive centre core could easily be produced with a length of resistance wire (what resistance does the Smiths gauges work on) inside a tube with a hole at the top and one at the bottom for the liquid to enter. The size of the holes would automatically create a damping effect. Anyone fancy having a try?
 
240-33 Ohm I believe. It appears that Fuel Safe do one on Special at $148.

So £100 plus shipping etc plays against £34.65 plus postage (for a traditional swing sender).
 

Sandy

Gulf GT40
Lifetime Supporter
The fuel safe one is made by Centroid and they are about $80 USD in any length and resistance range. I have them on several cars. They work by capacitance not resistance, but the magic electronics of the sender make it all right for what the gauge sees. You do have to run power to the sender unlike a pure resistance unit. They are excellent with foam in a fuel cell as you just need to poke a small hole and all done. One other gotcha is that if you car is an old timer and uses a pulsing gauge voltage regulator (my mustang did and sunbeam tiger did) you need to do some extra work to provide clean power to the gauge.

CENTROID PRODUCTS

Their site is a bit stale and old tech.

Sandy
 
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