Fuel level sender resistance

#1

Anyone happen to know what the empty tank resistance of the level sender should be? I’m seeing 0 for full and 59 ohms with the float at the bottom (and the low warning light on). But the gauge doesn’t indicate below about half scale (it does fall to below E with the key off).

The cluster has been pieced together with parts from others, so it is possible that my problem lies in the cluster. But to figure that out I need to determine whether the level sensor is operating properly and for that I need to know what resistance it should have when the tank is empty.

Oh yeah, the car is an 87 325is…

#2

I’ve had similar issues - I think the "e" and "i" gauges may be different too. I know that the late model cars used a second sender on the driver’s side of the tank that runs in series with the other sender.

I would suggest swapping out the gages and see if that works. Please share if you figure it out!
-Vic

#3

victorhall wrote:

[quote]I’ve had similar issues - I think the "e" and "i" gauges may be different too. I know that the late model cars used a second sender on the driver’s side of the tank that runs in series with the other sender.

I would suggest swapping out the gages and see if that works. Please share if you figure it out!
-Vic[/quote]pump side(I think) level sensor turns on the light the other one runs the gauge… Or it is reversed…bottom line is that one runs the light and the other runs the gauge.

#4

Sean,
I think that the light and one of the senders are all done from the passenger side. The passenger sender has 3 leads on its connector. One is power to the empty light, and the other 2 are for the resistor to read level. When a car is equipped with a second sender, that sender only has 2 leads - just for level, and they are connected in series with the first sender. That’s what the ETM says at least.

It may be that they’ve got some whacky variation on that - i dunno. After all, BMW did re-design pump/sender/tank for the E30.

-Vic

#5

victorhall wrote:

[quote]Sean,
I think that the light and one of the senders are all done from the passenger side. The passenger sender has 3 leads on its connector. One is power to the empty light, and the other 2 are for the resistor to read level. When a car is equipped with a second sender, that sender only has 2 leads - just for level, and they are connected in series with the first sender. That’s what the ETM says at least.

It may be that they’ve got some whacky variation on that - i dunno. After all, BMW did re-design pump/sender/tank for the E30.

-Vic[/quote]Vic is probably right. I wasn’t thinking it all the way thru…My 89 had a non working guage but the light would come on…

#6

An Update…

I found a reference in the TIS that says that the level sensor (an early car only has one) should be 3-72ohms. I’m seeing 0-59 so it seemed obvious that the sensor is bad. The new one should be in today and I rather expect it to fix the problem.

Now I need to see if I can clean the debris from the fuel tank. If I can’t I’ll have to replace the tank. There’s enough loose gritty stuff in the tank to cause fuel starvation by clogging the inlet screen when one throws the car around on the track.

#7

Good info - thanks!!
-Vic