early vs late fuel tank senders

[scottinAZ]

I have an 87 (late 86) 325, and recently got a fuel sender for a 91 with a bunch of other parts. My sender is finiky and would like to change it out.

Real oem shows the same sender for early and late tanks (pass side sender at least). How is the newer tank with the drivers side sender wired to work, is the pass side late model sender truly the same as the early single sender tanks?

Thanks

[Jean]

On cars with two senders they are wired in series, both are senders, one has 3 pins as it's got a switch on/off for the low fuel light.

[jlevie]

The right side fuel level sensor is the same for both tank variants. You can swap in the sensor from the 91.

[scottinAZ]

thats what I needed to know. RealOEM showed a split at 9/87, however the P/N was the same. Good to know that I have one I can use

[StereoInstaller1]

The right side fuel level sensor is the same for both tank variants. You can swap in the sensor from the 91.

I thought the '91 used Motormeter vs. early using a VDO (or the reverse of that) meaning an inaccurate guage, or something like that

[jlevie]

As far as I know the sensors are the same. But the gauges for the two tank variants are different. If you use an early gauge (for the single sensor tank) in a late model car, or vice versa, the reading will be inaccurate at less than a full tank.

[scottinAZ]

well, looks like I shall be the guinea pig on this one, Im swapping the senders in the AM. Will update this thread with results

[Jean]

The gauges are different,because early cars read from ONE sender and late model cars or the ones with 2 senders obviously read from TWO so they are calibrated fro different ohm scale.

[StereoInstaller1]

So his early car should read wrong with a single late sensor, unless he uses 2 sensors (keeps the ohm scale the same)...so get it done and we will all know!

[Jean]

You can't really put a late model sensor into the early tank, they are not the same size... the late model senser is used with the early sensor. The thin one (same on early and late model cars) is the one in the fuel pump housing, but the thicker one is on the driver side and it can only be used in that spot.

If you use late model gauge with early tank/sender = wrong reading. If you use early gauge with late model tank with 2 senders = wrong reading. They basically have to match.

[scottinAZ]

Only thing I will be swapping is the sender on the fuel pump assy (pass side on early car) if that doesnt work, the original sticky one will be going back in.

[Jean]

Both senders have to be in 100% working condition in order for the system to work properly, you may be installing a good sender but if the other sender is bad you won't solve the issue.

If your car has only one then you should be good, you can test the sender with an ohm meter you know.

[scottinAZ]

only have one sender (early model 55l tank). Ohmed out OK, but that doesnt mean squat if its sticking against the housing like my current one......... no biggie, its not like I have to drop the freaking tank like a domestic car to change the damn thing. Whomever put the access panel in there was a fucking genius!!!!!!

[scottinAZ]

ok, time to put this to bed...... I couldnt sleep, so I slaved in the sender from the 91, and it seems to work fine. I tipped the sender both up and down, and the gauge tracked without issues, and the low fuel warning, while somewhat intermittent, did work. I also installed the new sender, and show the same amount of fuel that I had before, so we will see if the new one tracks the tank properly, or if I end up walking because the damn thing doesnt work, and I run out, but that is the subject of another post for another day