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R1100RT Gas Tank Wiring


RK Ryder

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RK Ryder

Before I put the Tupperware back on the bike, I’d like spray the electrical connector from the gas tank to the fuel gauge with cleaner in the hope of having the gauge read more accurately. As I recall, I think that the connector is found tucked up under the front right side of the tank; am I correct? I’ve done this in the past but it has been a while. I keep hoping that one day the gauge will read full after a fill up.

 

Paul

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dirtrider
1 hour ago, RK Ryder said:

Before I put the Tupperware back on the bike, I’d like spray the electrical connector from the gas tank to the fuel gauge with cleaner in the hope of having the gauge read more accurately. As I recall, I think that the connector is found tucked up under the front right side of the tank; am I correct? I’ve done this in the past but it has been a while. I keep hoping that one day the gauge will read full after a fill up.

 

Paul

Morning Paul

 

It should be up under the R/H side.

 

If you want your fuel gauge to read correctly then you really should run a separate ground wire from the tank connector brown wire directly to the battery negative post. 

 

The ground wire is especially important if your fuel gauge reads higher with the key ON but lower with the fuel pump running (both the gauge & the pump share that brown wire ground circuit). 

 

You can clean & spray the connector pins and that can help but that won't cover for a high resistance ground circuit.  

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RK Ryder

Thank you Dirtrider.

 

The fuel gauge read full after a fill up for the first few years that I owned the 1100. After a master BMW tech relocated the fuel filter outside the tank, the gauge has always shown only 9 bars full. Basically I mentally add an additional bar to what the gauge shows but anxiety does set in when the fuel level starts dropping below the mid-point. Cleaning the connectors in the past has made no difference but hope springs eternal. 😂

 

Thank you again.

 

Paul

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dirtrider
30 minutes ago, RK Ryder said:

Thank you Dirtrider.

 

The fuel gauge read full after a fill up for the first few years that I owned the 1100. After a master BMW tech relocated the fuel filter outside the tank, the gauge has always shown only 9 bars full. Basically I mentally add an additional bar to what the gauge shows but anxiety does set in when the fuel level starts dropping below the mid-point. Cleaning the connectors in the past has made no difference but hope springs eternal. 😂

 

Thank you again.

 

Paul

Afternoon Paul

 

It could be inside the tank caused by resistance, or internally from a float problem, or externally as a resistance, or in the pump pass through as a resistance. 

 

You might be able to pin it down a little if you have a decent digital DC voltmeter by running a voltage drop test between the brown wire at the pump pigtail connector & the battery negative post (with the fuel pump running).

 

If you don't show a meaningful voltage drop on the brown wire then your problem is probably inside the tank, or in the pass-through solder connections, or even in the sliding float resistor wire area.

 

Why BMW shared the high amp fuel pump ground with the sensitive low of the fuel gauge sender is beyond me. 

 

Probably cleaning the big multi-ground connection point under the air box would a great place to improve the fuel sender low (grounding) but it is a LOT easier to just run a parallel ground wire between the fuel tank connector & the battery negative post.   

 

I have seen some difficult to get that last bar 1100/1150 motorcycles require a separate ground wire run to a clean spot on the pump pass through plate, then inside the tank split the fuel sender ground from the pump ground then attach that to a clean spot on the inside of the pump pass-through plate (eliminate the resistance areas & basically ground the fuel level sensor directly to the battery negative post)

 

Or, just mentally add an additional bar to what the gauge shows:classic_rolleyes:

 

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Michaelr11
11 hours ago, RK Ryder said:

keep hoping that one day the gauge will read full after a fill up.


Quick dry electrical contact cleaner.. Separate the two parts, clean each side. Clean them several times. Then, clean them again. I clean the connector on my RT each time I have the right side panel off. I have over 270k miles on the bike and 10 bars on the fuel gauge doesn’t switch to 9 bars until after 30 miles. There are no extra ground wires. Not saying that it wouldn’t help, but it’s not always needed.

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I separate the plug, use deoxit on it, then plug and unplug a couple of times, every time I have the right side panel off. I get full bars on a full tank for the first 20km. 

 

but there is no need to have fuel anxiety, the orange fuel light will tell you when you have at least 4 litres left. 

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13 hours ago, Michaelr11 said:


Quick dry electrical contact cleaner.. Separate the two parts, clean each side. Clean them several times. Then, clean them again. I clean the connector on my RT each time I have the right side panel off. I have over 270k miles on the bike and 10 bars on the fuel gauge doesn’t switch to 9 bars until after 30 miles. There are no extra ground wires. Not saying that it wouldn’t help, but it’s not always needed.

Morning Michael

 

But your motorcycle reacted to cleaning,    Paul stated   "Cleaning the connectors in the past has made no difference", so he has something else going on & this is most likely a resistance thing. Adding the parallel ground wire has been a good starting point on a number of problematic 1100/1150 motorcycles.  

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When I did the external fuel filter mod on my 1100r I found the loop of hose that’s fitted inside the tank, to bypass where the filter and U bend hose normally go, fouled the arm of the fuel level float. No matter how I twisted and twiddled I couldn’t get it all to fit together while allowing full movement of the float. 
Being clumsy and  impatient I eventually snapped the float off the switch, so no fuel switch now. 
I don’t know if your bike has the same level switch float mechanism, but maybe the hose is fouling its movement, not allowing it to reach the top? 

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8 minutes ago, King Herald said:

When I did the external fuel filter mod on my 1100r I found the loop of hose that’s fitted inside the tank, to bypass where the filter and U bend hose normally go, fouled the arm of the fuel level float. No matter how I twisted and twiddled I couldn’t get it all to fit together while allowing full movement of the float. 
Being clumsy and  impatient I eventually snapped the float off the switch, so no fuel switch now. 
I don’t know if your bike has the same level switch float mechanism, but maybe the hose is fouling its movement, not allowing it to reach the top? 

Morning King Herald

 

Different dog_

 

You have an (R) with a float for fuel level. 

 

We are talking about an (RT) that ONLY uses the float for low fuel level warning, the (RT) uses a separate (semi-sealed tube) with a sliding float inside to register fuel level. Nothing mechanical can get to the float & fowl it.

 

The internal float can get varnish build up, or the thin resistor wires can get oxidized or have resistance to the float contacts, or the float tube can get crushed at about mid point  from a fuel tank side suck-in due to a plugged vent or plugged evap can (USA thing). 

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