Kindly Help Fuel guage problem

Greetings all

one day my E46 318i simply didn't start I went to mechanic and he told me it's a bad fuel pump so he removed the pump and found a clogged filter (The one attached with the pump inside the tank) he changed that with an old one of his and it worked fine even better than what I remember.

After that day I found the fuel gauge giving totally false indication, It hesitates and gives a full tank while its definitely not full and fluctuates quickly through that simply it's gone crazy.

I thought maybe something happened to the sender in the pump while he was cleaning the filter so I bought a new one, but the same problem is there !!!!!

After internet searching I went to the cluster test and that I got :

098303 6.0

after one second

097305 6.0
after another second
098305 6.0
etc.
100305 6.0

101305 6.0

the readings fluctuate as u can see

0403 6.1

and 0404 6.1
and 0401 6.1

0412 2 -6.2

those are the readings I could have written and I made a cluster reset at the end

Can any body tell me what's happening plzzzz It's really bothering me not knowing how much fuel I do really have.

Thanks

There is a siphon jet pump on the left side of the tank (Driver side). It is nothing more than a tube with a check valve in it. If your fuel pump (on the passenger side of tank) is weak it will not suck hard enough to open the check valve and the fuel in the left side of the tank will never get sucked to the right side of the tank and you will run out of gas somewhere between half and a quarter of a tank.

I would change the fuel pump, but it could also be that the sucking jet pump tube was disconnected and simply not allowing the transfer of fuel from one side of the tank to another. So you might want to pull apart the Driver side first and inspect it to ensure your tube did not get disconnected between the two lobes of the tank. The Driver side also has a sending unit along with the jet pump. If it fails it will also give you a false fuel reading.

http://www.realoem.com/bmw/showparts...72&hg=16&fg=05

Look at number 1 in this photo (in upper right hand corner of photo)...it is your sending unit with the tube (sucking jet pump) attached to it...make sure it is in that configuration and not disconnected...

And how can this syphon valve affect the fuel gauge on the cluster ?? the car doesn't run out of fuel at some point but it just faulty reads the fuel level in the tank and how can I access to this part if the fuel is filling the tank ?

Btw I did change the fuel pump with a new VDO pump

Your problem started when you changed the fuel pump. You have two sending units...one on the pump and one on the other side of the tank. Since it occurred immediately after changing the pump, the sending unit on the pump may be inop/damaged or hung up on something. You may also may have disconnected the siphon tube.
Access? very carefully....you should drain it with an approved pump for that purpose...but I know it can be done by wearing gloves and working carefully in plenty of ventilation. You'll be able to lift it out of the tank and replace the sending unit same as you did the fuel pump.

A quick inspection of both sides of the tank will give you a clue...if they are not equally filled, then the jet pump is disconnected or the valve is stuck.

BTW...I would disconnect the battery too...so as not to create a spark and blow yourself up.

Originally Posted by QAfred

A quick inspection of both sides of the tank will give you a clue...if they are not equally filled, then the jet pump is disconnected or the valve is stuck.

So as not to spread misinformation, this statement if fundamentally and totally incorrect. The purpose of the sucking jet pump is to transfer all the fuel it can from the left side saddle tank over to the right side saddle tank where the fuel pump pickup is located.
As long as the right side fuel level is over the top of the bridge connecting the two sides of the tank, the fuel will flow back to the left side, recirculating the fuel over and over.
But when the fuel in the right side falls below the bridge threshold, all the left side fuel will be transfered over to the right side. Thus the right side can be close to full, when the left side is pumped empty.
Physics explains so much in life.

OP, if you've replaced the fuel pump and are convinced it is correctly installed and the sender is functioning properly, I'd say your next move is to replace the driver side sender.

Do know that some attempt to clean the sending unit contact wiper board with a pencil eraser to breathe some new life into a unit that has tarnished. Personally I prefer the quality of new parts.

doesn't those codes from the cluster fuel test mean any thing to anyone ? I think is a big clue

Originally Posted by GoForthFast

OP, if you've replaced the fuel pump and are convinced it is correctly installed and the sender is functioning properly, I'd say your next move is to replace the driver side sender.

Do know that some attempt to clean the sending unit contact wiper board with a pencil eraser to breathe some new life into a unit that has tarnished. Personally I prefer the quality of new parts.

Well I prefer that but I actually think the problem is in the tank pump side before I do any thing in he other side and have double trouble.
can I clean the new pump sender with a pencil eraser or a fine sand paper ? or that will not help.

Yeah, you can give a try to cleaning up the copper contact segments where the sender contact wipes with an eraser.
Use sandpaper and you'll chew up too much of the fragile thin metal.

Fine steel wool perhaps, but I'd be concerned that you'll get small pieces in the pump or tank. Clean well.

Originally Posted by GoForthFast

So as not to spread misinformation, this statement if fundamentally and totally incorrect. The purpose of the sucking jet pump is to transfer all the fuel it can from the left side saddle tank over to the right side saddle tank where the fuel pump pickup is located.
As long as the right side fuel level is over the top of the bridge connecting the two sides of the tank, the fuel will flow back to the left side, recirculating the fuel over and over.
But when the fuel in the right side falls below the bridge threshold, all the left side fuel will be transfered over to the right side. Thus the right side can be close to full, when the left side is pumped empty.
Physics explains so much in life.

Go forth-you may be correct, as I have never had to get into the Driver side of the tank.
However, I did not pull this info out of my ahole. It is on page 160-13 of my Bentley manual- 1999 to 2001 version as a Note at the top of the page, but nobody is always correct, not even the technical experts who write manuals.

Originally Posted by QAfred

Go forth-you may be correct, as I have never had to get into the Driver side of the tank.
However, I did not pull this info out of my ahole. It is on page 160-13 of my Bentley manual- 1999 to 2001 version as a Note at the top of the page, but nobody is always correct, not even the technical experts who write manuals.

Darn, and I was all set to have to apologize! I checked out my (newer) version of Bentley and it says nothing similar on the page you detail. A few pages later it does have a sentence about equalizing the fuel level, but it goes into zero detail.
I'm going to try to definitively research this, but in the absence of printed facts, perhaps I'll be graphing realtime OBC hidden function fuel tank readings to see how the twin saddles empty over time.
So for now we're both in the dark a little!

PS--I'd never pit my life on something Bentley said. We do a much better job of DIY's on e46 boards than Bentley. Sad fact of us caring more than they do. Hired gun and all you know.

That's wuts happening with me !!!!


still can't find an answer please heeeeeelp

but I've got another tip I found that from the cluster test that the first three numbers change rapidly for example "056263 6.0"to "118262 6.0" I know that this mean something but I really can't get a clue