Not sure to understand what you told.
I'd like to make sure that, in certain circumstances, the hole by which the
fuel tank internal pressure is balanced with the outside atm pressure, may
not be cluttered.
Following http://.bmwfans.info/original/z3/cou/ it's possibly the fuel tank
breather valve external orifice.
The url points to the 2.5 inst of the 3.0i.
Using the last 7 digits of the serial number I ended with the right model.
I'm focussing on the fuel tank breather valve and the active carbon
container which the upper tube is a fuel vent pipe.
Hovever, I'm wandering where to locate them and how they're interconnected
together and with the tank?
That is not entirely accurate. There is a "vent" of sorts built into the gas
cap that lets air into the tank, but prevents fumes from escaping the tank.
The idea is that a cacuum can develop, so there is a flap kind of thing in
the cap that will allow air to be sucked in, but this flap presses against
the small hole to keep fumes from escaping in the event the tank builds
My guess is, he got a Check light with a code from the P044n family of codes
that is telling him there is a Gross or Minor Leak. Odds favor such a code
to arise out of the improper securing of the gas cap during a recent fill
Does it suck or blow? The "---" is not vent related.
Let's do this, restate the trouble you are having, and we'll talk about the
causes. I do not think the problems you have given are based in venting of
the fuel tank, or lack thereof.
Thanks Jeff for the help.
The tank is under a slight depression.
I also read horrors about tank deformations on 2000 Z3 resulting in gauge
deteriorations and DTE issues.
Concerning the trouble: By accident, I refilled too much the tank although I
was aware not to do that. First the DTE was correct, pointing to ~520 km as
usual. Then 200 km later I noticed the "- - -" on the display, not blinking
as it does when there's an emmergency to refill.
Although the gauge was indicating 1/2, I stopped at the gas station and put
around 25 liters. The DTE didn't change and the gauge continued to decrease
like normal starting from the 1/2 until the light came on. Since, the needle
remains at zero, I refilled something like 8 times without any modification
on the displays.
The car has 98000 km on it, pampered and so. I already had issues at 50000
km but with the DTE only. It recovered by itself after 4 or 5 stops at the
gas station. At that moment I already noticed that the thank was under a
very slight depression.
The two problems look different. I can't manage to understand the link
between the fuel gauge and the DTE. For me, it's the same value sent to both
the gauge and the OBC to compute the DTE, based on the fuel consumption. As
far as the gauge provides a readable indication, the DTE should follow and
indicate a value accordingly. Otherwise the problem doesn't have the sender
as a root cause.
Since I can't understand the DTE failure, I'm keeping investigating several
ways: broken sender stuck against the wall of the tank, software error, bad
data stored somewhere, waiting for reset, ... I've just ordered the TIS on
e-bay to see how the circuits are wired. I also don't believe in a double
failure. It should be more a propagation or a consequence.
By the way, you talked about error code in your previous message. Where are
the error codes displayed on ? Do people read them using a tool or by
depressing buttons in a specific sequence (odometer, contact key, OBC reset
button, ... ) ?
Okay, now we have something to work with.
My E36 (a 325i) had this same problem. I would fill it with gas and it would
continue to display Empty. Sometimes as I drove and parked, then started
again, the tank would then read the current level, then drop as expected
while driving. It would eventually get to E, and remain there after filling
The trouble was, one of the two fuel level sending units (your car might be
different because it is a Z3) was dirty from sulpher or some other
contamination in the gasoline. In any case, I pulled the back seat out of my
car to access the gas tank through access ports inside the car, and removed
the fuel level sending units and cleaned the contact pads.
There is a contact strip that is stationary, and a wiper that is attached to
the lever arm. I used Contact Cleaner and a business card as the abrasive to
clean the contact and the wiper. You have to be careful to not bend the
wiper or your fuel level sending unit will be toast.
As you are working to pull the sending units, the obvious precautions will
become apparent -- do not damage the o-ring, make sure you put the parts
back in straight, etc.
On my car, the tank is under the back seat, on your car I would imagine it
is in essentially the same place, except you haven't got a back seat.
Perhaps your access to the tank will be through the trunk, I do not know.
After I took the seat bottom out and pulled back some tarpaper-like
material, there were two round access panels perhaps 4 inches in diameter
and held on with 4 screws. Under these panels, there are plastic rings that
have to be unscrewed, plumbing fixtures to disconnect and electrical
connections to unplug -- this will release the sending units. There are
o-rings here to be careful of. Assuming you have two sending units as I
have, the Right Side unit is also the fuel pump. When I did my car, I did
the left side first and got lucky because after I put the car back together,
the problem was solved and I did not have to take the right side apart.
If you take this problem to the dealership, they will replace the sending
units (one or both) at a cost of about $350 (for both) just for the parts. I
had no trouble fixing my own sending units for the price of a can of contact
Your car is an '02, so it is OBD II compliant. I'm not certain, but I think
this should be pulled through the OBD II data port with a standard
diagnostic scan tool. Autozone will pull the codes OR let you use the scan
tool to pull them yourself free of charge.
I think you have discounted the sending unit (I also think there are two of
them), whereas I think the sending unit is your trouble. There has been a
problem with the fuel sold in the southeast that is reported to coat the
fuel level sending unit's contacts with sulpher, which causes the sending
unit to stop working. These reports date back a year or so.
Thank you so muck for these details.
From the information I got on www.realoem.com, and similar sites, the car is
equipped with only one sender, part of the fuel pump. It's located behind
the passenger seat and the carpet needs to be cut.
The following url provides some information with pictures. One of them
represents the sender's tracks to be cleaned.
The message is in French, the forum needs free registration. Nevertheless it
may be of some help for somebody else (here's my contribution :-) ).
Correct, because of the discrepant readings on the DTE and the gauge.
Anyway, It's worth to give a try. Worst case: i'll have to buy another pump
at a price pretty lower than the stealer's intervention. Best case it'll
As soon as I receive the TIS, I'll start the surgery. Bye
The carpet comes already with a dotted line, look at the pics into the
message I gave the url to access to.
Quite sure that this is a huge work to remove the trims, I didn't check.
Since I have time waiting for the TIS, I'll proceed to some investigatation
I should clarify an earlier statement ...
I said the gas cap allows air to enter the tank but prevents air from
escaping. This is true. But, it takes a pretty strong vacuum to allow air to
be sucked in, this can cause the cap to make a sucking sound when it is
removed. This sucking sound is not only okay, it is desirable.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.