i have a 1998 540i6 and everytime it gets down to a 1/4 tank it starts to sputter and loses power.. cant figure it out.. some times it sends the code miss fire to certain cylinders.. can anyone tell me what this is coming from.. it only does it when it gets right below the 1/4 tank mark.. it will not make it to the point where the gas light comes on.. my computer still shows that it has like 80-100 milels left on the tank so i know its not out of gas unless the gauge is off...

if anyone has had this similar problem or has any insight on why it might be doing this would be very helpful... thanks

Maybe a weak fuel pump?

fuel pump in the tank or ???

any others suggestions....

Do you fill up when you reach the 1/4 tank level? If so, how many gallons does it take? Knowing the volume of your gas tank will tell you quickly if your gauge is off or not.

thanks good point what size is our gas tanks on the e39 540 that way i know...

Try changing your fuel filter first and possibly your fuel gauge could be off showing 1/4 when really on reserve.

Have the same problem on my 97 528i. Changed the fuel filter so its not that, at least in my case it wasnt. Also checked how much gas it takes to fill up when the sputtering starts to happen and it was several gallons less than the 18 gallons it takes to fill my tank, so thats not it. Also replaced recently, air filter, spark plugs, all 4 o2 sensors, CPS & mass air flow sensor. Anyone with any other ideas?? I was thinking a possible weak fuel pump as my next guess or a gas cap thats not holding pressure. I was under the assumption a fuel pump either works or it doesnt. Could it be the fuel pump?

Monitoring the pressure in the fuel rail will tell if that's the problem.

Well i think i found the problem. Today my tank went below 1/4 tank and of course started sputtering. I pulled over and took my gas cap off for about 30 seconds while it was running, put it back on and started driving. No more sputtering at least not yet. I think it may be the gas cap is not venting properly and is creating a vacuum in the tank when the gas gets low. From what i understand about gas caps is they are designed to keep vapor in and also to let air into the tank so that when the gas level goes down it does not create a vacuum. Going to get a cap tomorrow, fill up my tank and see what happens when i get down to about 1/4 tank. Will keep you posted, may take a couple days obviously before i get back down to 1/4 tank.

INteresting, I just posted a problem today, and never in a million years would have thought of this. I will go check out my gas cap right now! thanks!! :)

let me know how it works out.. i got a full tank right now.. and it will be a while before i could find out if thats my problem..

Well after reading the workings of a gas cap i thought it made perfect sense in that when the volume of gas goes down the volume of air needs to be dispersed in order to prevent a vacuum in the tank. Got a new gas cap today at about 1/2 tank and drove it all day. When it got down to 1/4 it started sputtering again. UGHHH! Is there a pick up tube attached to the fuel pump that could have loosened up and fallen off? So when the gas gets below a certain level and the pump is no longer submerged in fuel, the pick up tube (if any) isnt able to pump any more fuel below a certain level. I would think a weak pump would cause this problem regardless of the volume of fuel in the tank. Anything above 1/4 tank the car runs perfect. Going to look at some pictures of the fuel pump for this car and then take mine out to see if there is a pick up tube that may have fallen off. Maybe even try a new fuel pump. Will keep you posted.

well, theres nothing wrong with MY gas cap :( , and no sucking noises when i open it. and the problem still exists for me. I will fill the gas tank tomorrow, to see if this cures it. Not one person responded to my post! oh well - Sorry, i dont mean to hijack yours lol :)

darn.. ok... well keep me posted.. i would like to know.. im still thinking its the fuel pump or the hose on the fuel pump...ima try and look at some pictures tooo..

i fillied up today, it had a lil more that a 1/4 tank and it toook 12.8 gallons of gas.. does that sound right??

That sounds about right.

anybody else knows..????

Here's a long shot:

When I was in college, I had this '84 volvo 240 wagon that exhibited this exact same failure. It was the most puzzling thing. I discovered that there was a very small rubber connecting line (about 1/2") on the fuel pump that had corroded. When the fuel level was low, the rubber would allow air to get into the fuel line, and so the car would act as though it was possessed.

Sorry i havent updated this post in a while. Finally having time to get that fuel pump out and see what the deal is. Doing it this weekend. Will let you know if there is a tube that fell off or deteriorated. Im hoping that is the case.

I took out the fuel pump and there were no hoses which were deteriorated or that fell off. Time to get a new fuel pump and see if that solves the problem. Will be ordering a new fuel pump next week.

I took out the fuel pump and there were no hoses which were deteriorated or that fell off. Time to get a new fuel pump and see if that solves the problem. Will be ordering a new fuel pump next week.

yea man i really think thats the problem, but we will find out oonce you change yours out.. let me know how it works out.. thanks man

I have the same problem with my 97 540i6. Recently had my fuel pumps changed, and the problem kicked in. Taking it back to repair shop for diagnosis and hopefully repair. Will keep you posted!

thanks man.. keep me posted... really appreciate it

Just got a new fuel pump but after reading Skininsac's comment about the problem not being resolved after installing a new pump makes me want to hold off and maybe get my money back for the pump. PLEASE keep us posted...

Just got a new fuel pump but after reading Skininsac's comment about the problem not being resolved after installing a new pump makes me want to hold off and maybe get my money back for the pump. PLEASE keep us posted...

Possible bad sending unit. Access Test #6 in your instrument cluster to see how much fuel is in each tank & what is being transfer.

Two things to check. The saddle tank in your car has only one fuel pump, but two level sensors - one for each side and it averages the two to give you a reading (i.e. one side full and one side empty = 1/2 tank; one side half full and one side empty - 1/4 tank). Anyhow, there's a siphon that operates off vacuum created by the pump and pulls fuel from the non-pump side. It's attached to the level sensor in the non-pump side (driver's side). If this siphon of any of it's lines are damaged, it won't pull fuel from the non-pump side of the tank (think : trying to suck through a straw with a slit in it). Other thing to check is the pressure regulator and the 3/2 valve (return regulator). Pressure regulator is part of the fuel filter and the 3/2 valve regulates fuel pressure returning to the tank.

has this been resolved yet? I'm really curious to find out the cause...

The pressure regulator is part of the fuel filter?? Im a little confused. I did change my fuel filer recently. Anyway where are these regulators located? Im not even sure what the 3/2 value is??

Hello all.

I'm searching the forums and this is the exact same problem I was looking for. I've had my 98 528i for three weeks and it started doing the same thing last night. This morning it started and drove fine until it got a little warm and then it didn't want to idle. It died on me and I had to get it towed. I did notice that I had a little under a 1/4 tank gas but I had the car lower than that before (to the point that the gas light came on) and the car didn't shut off. I'll be watching this thread closely.

yea any suggestions guys will be very helpful.. does anyone know yet??

no one yet??

Well here it goes. I have read in these forums that on some cars there is a small electric motor device that pumps the gas from one side of the tank to the other. That is not true in my car. I took the sender out from the drivers side as well as the fuel pump/sender on the passenger side. I took out the suction jet that is connected to the sender on the drivers side, inspected all the tubing. All looked good. I blew some low pressure air through the gas line that is hooked up to the drivers side unit, cleaned the entire suction jet assembly out with aeresol cleaner and blew air through all of the tubing and reassembled. Ran down to near empty and NO PROBLEMS!!! I even got the gas light to come on which has not happened in a real long time. Must have had some debris in the suction jet assembly. Good as new!! Hope this works for you Nsty540!!