Fuel gauge
Moderator: martauto
Hi, trying to get this project finished.
The last "push".
Fuel gauge reads nothing, I've bridged the pump side and it reads half.
Is the pump side faulty or just the sender side?
Later car with pump on 1 side, just sender on other.
Fanks
The last "push".
Fuel gauge reads nothing, I've bridged the pump side and it reads half.
Is the pump side faulty or just the sender side?
Later car with pump on 1 side, just sender on other.
Fanks
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- E30 Zone Regular
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I’ve got the opposite problem, mine always reads full
BMW E30 316 ‘87
BMW E30 325i ‘88
Bristol, UK
BMW E30 325i ‘88

Bristol, UK
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Following.
Last time I used mine it was flickering all over the place and then died.
The low fuel light still works but its now stuck on the bottom.
The MPG gauge is also intermittent im wondering if this could be linked to failed SI board batteries ?
Last time I used mine it was flickering all over the place and then died.
The low fuel light still works but its now stuck on the bottom.
The MPG gauge is also intermittent im wondering if this could be linked to failed SI board batteries ?

e30topless said : Proper BMW's have 4 headlights, last of the run was the E30 and E34/E32 anything after that is just complete shite
- Brianmoooore
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RH sender is faulty (or the wiring to it). Possibly repairable.
- Brianmoooore
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Even with the tank less then half full?
- Brianmoooore
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MPG gauge could be, but not normally the fuel gauge, unless the batteries have leaked really badly.
First test for the gauge is to bridge the sender wires at the pump assembly.
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Yes everytime I start her up it reads full for first 10 mins. Then sometimes it pings to correct reading
BMW E30 316 ‘87
BMW E30 325i ‘88
Bristol, UK
BMW E30 325i ‘88

Bristol, UK
- Brianmoooore
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What happens if you pull the sender plug off at the fuel pump?BristolE30 wrote: ↑Fri Jun 05, 2020 7:14 pmYes everytime I start her up it reads full for first 10 mins. Then sometimes it pings to correct reading
- Brianmoooore
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IF it ALWAYS reads half, then both sides are dud. LH one is open circuit, and RH one is stuck on empty.
What happens if you link out the RH one as well?
I had the same issue. I opened the instrument cluster, took the fuel gauge out (one nut to remove) and cleaned the connection between the fuel gauge and the cluster itself, which is made by contact around the screw area (sorry if I don't have all technical terms, French here...).BristolE30 wrote: ↑Fri Jun 05, 2020 7:14 pmYes everytime I start her up it reads full for first 10 mins. Then sometimes it pings to correct reading
This connection is the ground connection for the fuel gauge, as is illustrated in the electrical troubleshooting BMW document (that can be easily found on the web, and a great tool!). Then assembled everything again and working like a charm since. ;)
What happens is that since this connection is not working, then the current applied to the fuel gauge goes through the "full" position only (hence the "full" reading), nothing goes through the sensor loom. The sensor loom is the one that drags the indicator all the way between full to empy thanks to a variable resistor.
I agree that if it ALWAYS reads half, then both sides are faulty.Brianmoooore wrote: ↑Mon Jun 08, 2020 2:24 pmIF it ALWAYS reads half, then both sides are dud. LH one is open circuit, and RH one is stuck on empty.
What happens if you link out the RH one as well?
Passenger side for sure, since after bridging it, the gauge now gives a reading, so opting for a faulty sensor rather than a faulty wiring.
Under current wiring (passenger side bridged), if the reading moves (half to low) as fuel is used, then replacing the passenger side should do the trick. Otherwise, driver's side may be stuck in a specific position. Maybe worth taking it out and trying to unlock it. Otherwise, replacement.
The low fuel light working means the wiring is correct, this is just the display that is faulty, and highly likely this is a contact issue. As previously answered to another one, open the instrument cluster, take the fuel gauge out, clean the contact between the fuel gauge and the cluster, put everything back together and it should work.
For mpg, it may just be connections in the connectors at the back of the instrument cluster. I have new batteries on the SI board, and sometimes had same issue. I cleaned every contact at the back of the cluster, and now it is working fine.
- Brianmoooore
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Excellent English, an excellent description of exactly how the system works, and almost certainly an exact diagnosis of the problem in this case.Banban3 wrote: ↑Wed Jun 10, 2020 10:04 am
I had the same issue. I opened the instrument cluster, took the fuel gauge out (one nut to remove) and cleaned the connection between the fuel gauge and the cluster itself, which is made by contact around the screw area (sorry if I don't have all technical terms, French here...).
This connection is the ground connection for the fuel gauge, as is illustrated in the electrical troubleshooting BMW document (that can be easily found on the web, and a great tool!). Then assembled everything again and working like a charm since. ;)
What happens is that since this connection is not working, then the current applied to the fuel gauge goes through the "full" position only (hence the "full" reading), nothing goes through the sensor loom. The sensor loom is the one that drags the indicator all the way between full to empy thanks to a variable resistor.
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Thankyou for this I will try this first and report backBanban3 wrote: ↑Wed Jun 10, 2020 10:17 amThe low fuel light working means the wiring is correct, this is just the display that is faulty, and highly likely this is a contact issue. As previously answered to another one, open the instrument cluster, take the fuel gauge out, clean the contact between the fuel gauge and the cluster, put everything back together and it should work.
For mpg, it may just be connections in the connectors at the back of the instrument cluster. I have new batteries on the SI board, and sometimes had same issue. I cleaned every contact at the back of the cluster, and now it is working fine.


e30topless said : Proper BMW's have 4 headlights, last of the run was the E30 and E34/E32 anything after that is just complete shite
- Brianmoooore
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Not so, I'm afraid. The wiring for the gauge and light is completely separate from each other, other than a common earth wire from the RH sender to the earth point on the LH side of the rear seat. Having said that, the wiring for either doesn't normally give trouble.
Yep, correct, went too fast! Thanks for the correction!Brianmoooore wrote: ↑Wed Jun 10, 2020 9:30 pmNot so, I'm afraid. The wiring for the gauge and light is completely separate from each other, other than a common earth wire from the RH sender to the earth point on the LH side of the rear seat. Having said that, the wiring for either doesn't normally give trouble.
Low fuel is only on the pump side indeed.
Sorry for that, I had my issue in mind when everything worked fine (including low level) except the gauge itself (OBC fuel level was correct, so I knew the wiring was correct).
Thanks again for the correction.

Giving it a second thought, based on Brian's correction, before tearing apart the instrument cluster, you may want to check the following continuities first, at the C2 connector (the white one on the back of the cluster). Make sure you check for high resistor values, to avoid false negative results (you are not looking for a simple wire continuity, but for continuity through resistors):
- Since your low level light is working, you should have continuity between pins 6 and 5.
- Then check continuity between pins 6 and 4 (full side of the gauge), and between pins 6 and 16 (empty side of the gauge).
- If there is continuity for both combinations, then there should be no need to open the cluster and your issue is between pin 4 and the sensor on the RH side (other tests then to perform, such as bridging sensors).
- If either combination does not show continuity, then you may want to clean the contact between the gauge and the cluster to ensure continuity first.