Fuel Tank level sender issue

loanheadhouse · 03-15-2020, 05:47 AM

Okay so i'm on a F31 320D manufactured Dec 13 . Car runs/ drives fine but fuel gauge is displaying wrong information . Issue is with fuel tank and signals sent from it about fuel level. Nb This issue Is common with many other 1 / 3 /4 series diesel engined cars of a similar age as they all use the same tank and pump and level measuring components / methodology.

There are two fuel level measuring devices in the 'saddle' type fuel tank - 1 in each side of the saddle. Problem is that the LH side level measuring equipment is not accessible with tank in car as inside the car under rear seat squab there is only one access 'hatch' - which is on the right and has the main low pressure fuel pump directly below it [ and the RH fuel level measuring is part of that assembly].

Looking at pictures [ on ebay] of the tank from a F series diesel there is a round cover where the LH level equipment is going to be located.
Nb I have already established the LH unit is causing my problems [ and i've replaced the rh one anyway as its easy to do].

SO - my questions:
1. Can anybody tell me if the LH tank cover is actually removable or has it been welded or glued in place at manufacture ie is it worth dropping the tank so that i can get at it ?

If thats a no no then thoughts on a plan B are:
2. Electrically both float levels connect to the low pressure fuel pump. I could fabricate a connection so that the RH float feeds an electrical signal to both the LH & RH connectors. [ Obviously i'm only then getting a RH reading but i can live with that as the LH fuel is pumped to the RH anyway ]
But as it is resistance that is being measured how would the ECU interpret that? [ i'm not very good at electrical stuff] Any electrical experts out there? HighlandPete?

Can post pictures of tank / sender if anyone wants to see what i'm on about

All help appreciated!

dmaxdmax · 03-15-2020, 05:53 AM

I don't know about diesels, per se, but with the gas engine, the fuel pump and sending unit use a 'hall sensor' and get gunked up...sometimes 'hang up' and send the wrong level. Many e46s have run out of gas because they thought they had a quarter tank, when they had none.

I use Techron fuel system treatment...same as bmw stuff. Not sure what analog might work for a diesel, but I'm sure there's some...and maybe, over time, it'll start working again without your needing to rip into it at all.

In the meanwhile, just estimate your fuel needs based on mileage.

loanheadhouse · 03-15-2020, 06:00 AM

Thanks but have tried the 'non evasive' approach! Have been filling it every 500 miles to ensure i dont run out but want to actually fix it.

03-15-2020, 05:47 AM	#1
loanheadhouse Registered 2 Rep 4 Posts Drives: F31 320D Msport 2014 Join Date: Jul 2019 Location: Scotland iTrader: (0)	Fuel Tank level sender issue - input requested Okay so i'm on a F31 320D manufactured Dec 13 . Car runs/ drives fine but fuel gauge is displaying wrong information . Issue is with fuel tank and signals sent from it about fuel level. Nb This issue Is common with many other 1 / 3 /4 series diesel engined cars of a similar age as they all use the same tank and pump and level measuring components / methodology. There are two fuel level measuring devices in the 'saddle' type fuel tank - 1 in each side of the saddle. Problem is that the LH side level measuring equipment is not accessible with tank in car as inside the car under rear seat squab there is only one access 'hatch' - which is on the right and has the main low pressure fuel pump directly below it [ and the RH fuel level measuring is part of that assembly]. Looking at pictures [ on ebay] of the tank from a F series diesel there is a round cover where the LH level equipment is going to be located. Nb I have already established the LH unit is causing my problems [ and i've replaced the rh one anyway as its easy to do]. SO - my questions: 1. Can anybody tell me if the LH tank cover is actually removable or has it been welded or glued in place at manufacture ie is it worth dropping the tank so that i can get at it ? If thats a no no then thoughts on a plan B are: 2. Electrically both float levels connect to the low pressure fuel pump. I could fabricate a connection so that the RH float feeds an electrical signal to both the LH & RH connectors. [ Obviously i'm only then getting a RH reading but i can live with that as the LH fuel is pumped to the RH anyway ] But as it is resistance that is being measured how would the ECU interpret that? [ i'm not very good at electrical stuff] Any electrical experts out there? HighlandPete? Can post pictures of tank / sender if anyone wants to see what i'm on about All help appreciated! __________________ The E30 was replaced by an E36 325tds which was replaced by a E46 320d touring which was replaced by an E91 320d . Then my F31 320d msport arrived ..... but i'm still driving my E91.....and ignoring the F31!!!
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03-15-2020, 05:53 AM	#2
dmaxdmax Captain 417 Rep 923 Posts Drives: 2016 M235i 6-spd Join Date: Jan 2020 Location: New Jersey iTrader: (0)	I don't know about diesels, per se, but with the gas engine, the fuel pump and sending unit use a 'hall sensor' and get gunked up...sometimes 'hang up' and send the wrong level. Many e46s have run out of gas because they thought they had a quarter tank, when they had none. I use Techron fuel system treatment...same as bmw stuff. Not sure what analog might work for a diesel, but I'm sure there's some...and maybe, over time, it'll start working again without your needing to rip into it at all. In the meanwhile, just estimate your fuel needs based on mileage. __________________ '92 325i, '99 328i, '16 340i, '16 M235i all manuals dmax on FB My last pre-covid standup set
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03-15-2020, 06:00 AM	#3
loanheadhouse Registered 2 Rep 4 Posts Drives: F31 320D Msport 2014 Join Date: Jul 2019 Location: Scotland iTrader: (0)	Thanks but have tried the 'non evasive' approach! Have been filling it every 500 miles to ensure i dont run out but want to actually fix it.
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