Tank ventilation problem

[bzoli]

Recently I have problem stating up my car ('95 530i). The problem started a cold morning, after I used the car for approx. 80mile trip the day before. I was not able to start it up; I have tried at least 8 times before I gave up. In the evening I spend a couple of minutes trying to figure out the problem, when I noticed that the fuel gauge shows empty tank (it was half full). From that moment I have problem starting the engine. If it starts sometimes I experienced hesitation under acceleration and rough idling (Engine Check #1222). After a couple of days I figured it out that this is a fuel problem, I was not able to smell fuel vapor after several attempts to start up the engine, I have checked a spark plug and it was dry, no taste of fuel.
I thought the fuel pump is the problem. I have checked fuel line (just on/off, not pressure test) and intake manifold as well.

The rough idle (and #1222) can be explained with intake manifold vacuum leak, which I have tested. The rear of the intake manifold seems a problem. But this did not develop over night. So I kept looking what the problem could be after I checked the intake (seems one of the most popular problems in the topic). The check engine light goes away after warm up anyway, so that should not prevent the engine from starting up at least alone….

In the mean time I have noticed that if I let out the vacuum from the fuel tank the engine starts up right away. I have tested, if I open the tank and let air in, the engine starts without a problem.
What could be the problem?
Is this a fuel pump problem? The pump starts to fail since it is not able to deliver fuel if there is a vacuum in the tank?
Or it completely normal and the problem is the tank ventilation? Could it be so severe that the engine fails to start? A certain level of vacuum is normal, always can be heard during the fill up, right?

Opinion?

[BillionPa]

charcoal canister.

sounds like the fuel pump is failing though, exactly what you said about pumping against the vacuum.

the problem is related to low sulfur fuel, using an upper cylinder lube is a good substitute, but the pump is probably damaged beyond saving.

[bzoli]

charcoal canister.

sounds like the fuel pump is failing though, exactly what you said about pumping against the vacuum.

the problem is related to low sulfur fuel, using an upper cylinder lube is a good substitute, but the pump is probably damaged beyond saving.

Thanks for the reply!
I have been using the car since I posted the problem, by opening the tank every time, worked until yesterday. Started right up in the morning (approx. 32degF) got to work, after work (it was 65degF!!) I was not able to start up anymore.
1) The engine starts but stalls almost immediately, if not it is rumbling, by giving gas sometimes it revs up, but it is very hesitant, and back firing, sometimes just stalls.
After several starting-stalling attempts definite fuel can be smelled. Just because of this I guess there is fuel delivered, maybe not the right amount, hence the stalling, hesitation and the back firing.

2) I have checked the carbon canister across the forum, but it's still not entirely clear to me how it works. How does this effect the tank ventilation? Where is the canister connected, tank to intake manifold? It has to be a valve, which openes or closes based on intake manifold (one end?) and tank pressure (other end?). If is clogged there is no tank ventilation, right? Therefore the tank pressure could increase or decrease based on fuel level, ambient temp etc… right?
Basically what the symptoms are a failing carbon canisters? How does is affect the fuel supply/ fuel pump operation?

Do I have two problems in the same time, or all these symptoms are related? Or one caused another….

Any opinion?

Thanks very much,
Zoltan

[632 Regal]

ever change the fuel filter? the canister could be clogged, gaskets leaking and a weak pump from a clogged canister or filters, you might have a few things going on here.

[bzoli]

ever change the fuel filter? the canister could be clogged, gaskets leaking and a weak pump from a clogged canister or filters, you might have a few things going on here.

Never, and I guess nobody did ...
I have the car the since this spring, and I put approx. 5-6k mile to the car.

I have order them (there are two, right?), they are somewhere near the left rear of the car. I don know exactly where.
You are right clogged filter could lead fuel delivery problem.

[632 Regal]

yes 2 of them behind the right wheel well. Some of these guys have replaced them without drinking a bunch of fuel, I chose the swap and spill method (sucked). I dumped the filters out into a bucket and a LOT of black stuff drained out, the fuel was black.

They are also directional, make sure you note the direction of the old ones.

[bzoli]

yes 2 of them behind the right wheel well. Some of these guys have replaced them without drinking a bunch of fuel, I chose the swap and spill method (sucked). I dumped the filters out into a bucket and a LOT of black stuff drained out, the fuel was black.

They are also directional, make sure you note the direction of the old ones.

Jeff
What I still don't understand that how the carbon canister relates to my problem …. clogged canister effect tank pressure or not? This system let fuel vapor to the intake manifold, right? Not the other way around, air into the fuel tank …. so how get air into the fuel tank, anyway?
I just didn't get it.

Reading my original post, what could be the problem?


Thanks!!

[genphreak]

When the car won't start, remove the fuel vapour line from the charcoal canister (beware of flash danger!!! so no smoking!)

See if that releases the pressure in the tank. Normally the ECU operates a purge valve on the engine that draws gases from the tank using engine manfold vaccum to occasionally suck some gas through the canister. The activated charcoal is there to remove bad things from the gas before the engine combusts it.

By doing this regularly every trip, pressure is not allowed to buildup in the tank, and often a vacuum can. The vacuum is not very strong, because the next time the engine tried to suck through the canister the vacuum will prevent it- in fact it may even allow fuel vapour from the manifold into the tank.... I am not sure but I doubt this.

When you fill your car excess vapour is forced into the vapour tank just above and beside the gas tank (in some countries however the filler is open to the atmosphere. In the US they seal the nozzle to stop the customer getting cancer from the Benzene cloud as they fill the car) but since this is not 81 litres in size I don't know what happens to the other 70 odd litres of vapour if you were filling from empty... anyway... bottom line is you often find the tank has a small vacuum- it will obviously occur as the fuel gets used up as the system is sealed. It may be that the only breathing it can do once filled is through the charcoal canister... and as a result a clogged canister may cause problems? I don't think it all adds up every time but they design the thing to work within certain limits and some vacuum is acceptable, we all notice it when driving our cars long distance and stopping to fill up.

Perhaps one of the other guys will correct the flaws in my explanation... I know it doesn't quite add up. My guess is that the purge valve actually allows air back into the tank at times... perhaps at time of low manifold pressure, or maybe there is another valve I don't know about... I think there is one on the canister itself- maybe that vents the system.

Anyway, I wouldn't be too worried about vacuum in your tank unless the car generates it itself at times when you have not used much gas and the ambient temperature has not changed much. If it does this, there must be a very weird fault in the recirculation system and you should change the canister (we should all do this every few years) and inspect and test every single valve you can find in it.

Maybe consult the BMW TIS for such faults too. You'll need the ETK to find all the purge valves.

But my guess is that it is your clogged up fuel filters. As I said, vacuum in the fuel tank is a product of many factors and is probably normal. :) Nick

[brosher]

When you change the fuel filter add on an external check valve to the fuel line. This helped with my cold starting on my M60. Now that I have done that and the intake gaskets it starts and idles perfect. :) Also, verify on realoem.com whether you have 1 or 2 fuel filters. I think the late production M60's only had one.

p/n for the check valve is 16 14 9 068 988 and its only a couple bucks.

[bzoli]

Thanks!
I will post updates as soon as I have something.
I have order a fuel pump, pressure regulator valve and fuel filter.
Once it starts up and got home, I will change the carbon canister as well.

I have checked out realoem.com to get an idea of the vacuum lines
What does this do?
http://www.realoem.com/bmw/showparts.do?model=HE13&mospid=47406&btnr=11_1543&hg=11&fg=45
Because this http://www.realoem.com/bmw/showparts.do?model=HE13&mospid=47406&btnr=16_0184&hg=16&fg=10
is the carbine canister, but where is that purge valve?

[BillionPa]

the air pump is a completely independant system.

on the canister diagram, the top tube on the canister goes to the purge valve, which in turn is connected to the intake manifold.

the way the canister works is it traps the vapors from the tank, then lets it back into the intake by mixing it with air that it sucks from the other side (with no tubes). that side is connected to tube 6, which clips to the side of the car under the bumber.

if the canister is unable to suck in air through the bottom, when the purge valve opens up under cold start, instead of it sucking air through the bottom, it sucks it through the fuel tank line! and also the canister is unable to alleviate the vacuum in the tank so the effect is even higher.

when changing my canister, it weighed 3 times as much as the new one, and was heavily rusted. there was salt crystals all over the bottom, it was toast. after changing it the idle better, but it was harder to start the car (no absorbed vapors int he canister yet)

one thing i did notice was how bad the fuel lines were. i have a bag of them for the rear end of the car the next time i change the fuel filters and put in my new pump and sending unit, but i still need to order ones for the engine bay (bunch of em on the canister, a few on the fuel rail)

[bzoli]

Earlier last week I have replaced the fuel pump, one day later I was not able to start up the car again! I had to put a small can of gasoline to be able to start up, although I was sure that there is gasoline left in the tank. When I replaced the fuel pump the level was approx. ½, and I only drove 50miles. Anyway I went to the gas station to fill up fully I could only manage to tank 10 gallon, so it wasn’t empty.

During the weekend the fuel filters were replaced as well. After a couple of minutes test drive I checked the fuel lines for leaks, I got hand and knees looking at the bottom of the car from the back when I realized the problem, I could not believe, but it finaly make sense everything.
The fuel tank collapsed exactly where the fuel pump is!!
That explains why I found the fuel sender in pieces, why I was hardy able squeeze the pump to its place, and why the pump failed to deliver fuel while there was gas in the tank. The pump sits in the top of the dent, that's why….

I have searched the forum, and I have found a couple of cases when the same thing happened.

I will try to post a photo to see it.

The funny thing that I'm sure I wasn’t hit anything, it is something else ……

[bzoli]

Any idea or experience how to fix the tank above?

[E34-520iSE]

Wow I've never seen a tank implode before!

[Milkboot]

I have heard some people tell me "BEWARE" you have a plastic gas tank, but after changing my fuel pump 2 weeks ago, i know i have a metal one. is yours a plastic or metal one?

[bzoli]

Metal....