Fuel Gauge jumps when RPMs move: Video added

[motorsports_3]

My fuel gauge doesn't seem to work on my car. At first my fuel light was always on, but I noticed that the harness that has three pins was in upside down. Once I corrected that, the fuel light turned off but the guage still doesn't seem to be responsive. When you turn the car on it ever do slightly moves.

I have replaced both fuel sending units on my car. The one on the drivers side with two pins, is brand new. I bought a used one that goes on the passenger side, which has three pins. I have also replaced the cluster as well.



It is an 88 325 BTW.

Thanks

[motorsports_3]

Bump. Symptoms updated

[bernzpeed]

gas gauge needs replacement.

[jlevie]

This could be a wiring problem between the cluster and the tank. A few minutes of work with an ohmmeter will tell where the problem is.

[motorsports_3]

That's what I am beginning to think. When I play with the wires the gauge jumps. Do you have any advice on how to test that?

[STAGGERED M3]

if you need to fix the Cluster I might have a spare one from a 325e. I might also have the wiring you need if you can't make it to a Upick, but we will have to go through a molested wiring harness I have from my e30 m3.

[motorsports_3]

^ Thanks dude, ill let you know. I do not think it is the cluster, I had an extra one and swapped it out, which did nothing, unless that one was bad as well, lol.

This is really starting to get to me. I need to get to the bottom of this!

Could someone tell me the purpose of each sender? The one which attaches to the fuel pump is only there to trigger the reserve light, while the two pin one actually give you fuel level readings. Is that correct?

When you turn the ignition you see the gauge move ever so slightly so I know it is getting power, and it sometimes jumps sporadically and stays in the proper place. It seems like something is loose, a connection or what not.

[Jean]

The sender on the passenger side is 2 pin, it's like a variable resistor... The sender on the driver side is just like the one on the passenger side PLUS it's got an on/off switch for the low fuel light. The two senders are wired in series with each other, so if one is bad or faulty it will effect the overall result. BOTH have to be in working condition.

[motorsports_3]

The sender on the passenger side is 2 pin, it's like a variable resistor... The sender on the driver side is just like the one on the passenger side PLUS it's got an on/off switch for the low fuel light. The two senders are wired in series with each other, so if one is bad or faulty it will effect the overall result. BOTH have to be in working condition.

So do you think that since the 3 pin was plugged in upside down (some how) keeping the fuel light on at all times, that it could of possibly damaged the 2 pin sender? I replaced the 2 pin with a brand new one, approx 3 years ago, and have replaced the 3 pin with 2 used ones with no difference.

I used to drive the car a lot, before I painted it, and if I remember correctly the gauge worked properly, just with the gas light on at all times because of the upside down plugged in harness. For some reason when I took everything apart to diagnose it this time, the 3 pin was disconnected though.

[Jean]

So do you think that since the 3 pin was plugged in upside down (some how) keeping the fuel light on at all times, that it could of possibly damaged the 2 pin sender? I replaced the 2 pin with a brand new one, approx 3 years ago, and have replaced the 3 pin with 2 used ones with no difference.

I used to drive the car a lot, before I painted it, and if I remember correctly the gauge worked properly, just with the gas light on at all times because of the upside down plugged in harness. For some reason when I took everything apart to diagnose it this time, the 3 pin was disconnected though.

Most likely no, to your first question. Your next logical step would be to check the wiring FROM the sender connectors to the cluster. The SI board affects the Temp gauge, but the fuel gauge from what I remember seeing in the electronic schematics is wired directly to the sender(s)....

If the senders are ok, wiring is ok, then problem is in the cluster, it's a fairly simple system. The issue is with two senders you have 2x as many possibly issues where the problem may be (extra sender, extra connector/wiring).

[motorsports_3]

And to get to the wires I need to drop the fuel tank, right?

[motorsports_3]

Here are videos of what it does. The sound doesnt work. Im revving most of the time, as you could see in the video that shows the tach

[motorsports_3]

New videos

[Jean]

Unplug the sender(s) and tell us if the gauge still goes up to the same spot.

[motorsports_3]

Unplug the sender(s) and tell us if the gauge still goes up to the same spot.

Both senders?