Cannot fill up gas tank

[Classiks]

Hi,

I've searched quite a few forums and can't seem to get an answer. The closest I got was an E36 experiencing the same issue but I dont' think I have the same problem as he had fuel leaking from the o-ring under the rear seats.

I don't have fuel leaking or have fuel smell. When I go put gas in the car I can only fill up to 40 litres (10 gallons) and the pump will stop. If I try to slowly add more then the fuel backs up through the fuel filler.

I'm guessing it is more or less a venting problem as there is too much pressure and the fuel gets backed up. My question is does anyone know which vent hose it is? If it's related to the expansion tank or if it maybe the breather valve instead? Not sure what is common to go on the E30. Or if this would have anyway to do with the senders.

Thanks in advance

[Robotin]

IIRC e30's only have like a 12 gallon tank..

r u sure you are not just over filling it?

[Classiks]

IIRC later ones have a 16 gallon tank (62 litres) and I think the earlier ones have 55 litres (14 gallons). I'm sure I'm not over filling. The gauge always reads 40 litres when the pump stops.

I'm pretty sure it's a vent tube that's pinched, either the one that vents outside or the one that goes to the charcoal canister. Or the charcoal filter is clogged. But I actually don't know the location of these vent tubes to check...

[jlevie]

The tank vents via the charcoal canister and the collection of parts in the right side rear wheel well. But It sort of sounds like that isn't the problem. When the tank isn't venting properly the pump nozzle will kick off, but you can fill the tank by feeding fuel in slowly. The fuel appearing in the filler when you slowly add fuel sounds more like the tank is actually full. It would be interesting, and probably illuminating, to drain all the fuel from the tank, add a measure quantity (say 5 gallons), and then see how much fuel the pump puts in.

BTW: what car is car is this?

[603Racing]

I've seen this happen... with my e24 race car. In my situation the bottom of the fuel tank had been pushed in by contact with a tire wall. Resulting in a 18 gallon tank only taking in about 16 gallons from bone dry. Yes, it was pushed in that much. No, I wasn't the one in the car when it happened. :)

In your case I am thinking jlevie is on to something. When my e30 gas gauge reads empty, I'm lucky to get over 10 gallons into my tank unless I drive for a while on E.

[vpilarrt]

The later (90, 91) US 318is have the 55 liter tank. Which car do you have?

[KillaCam]

someone jacked your car up on the gas tank

[SmokeE30]

ive seen e30's with 10 gallon tanks, 83 320i tc baur doesnt even have a dropdown part on the drivers side

[Classiks]

Hey guys sorry I have an 89 325i built in September '88. The gauges says 62 litres.

Dented gas tank eh, well I'm under there right now attempting to install my sport shocks and struts. I just go the car not long ago, it was winter driven. The diff is all rusted and so is the bolt. I really wish BMW didn't make you drop everything in the back just to free the trailing arm enough for the spring to pop out. Anyway thats another story.

It doesn't seem like my tank is dented from under there but I'll look again tomorrow. I removed the plastic piece in the passenger fender and nothing seems pinched. Where exactly is the charcoal filter on this car, is it in the engine bay? Behind the plastic cover all I see are hoses and if I'm not mistaken the expansion tank.

I would like to take a good look at the charcoal filter as that could be the culprit.
If my tank is actually full but my gauge is always reading 40 litres...then I'm getting some really bad gas mileage!

Another thing I should add is that the car is hard to start from time to time. Sometime it takes 4 or 5 turnovers to start, sometimes it starts instantly. This mixed with my fuel filling issue makes me think perhaps they are related?

I recently changed all my plugs, fuel filter, oil filter, did a compression check (175-180 each cylinder), and bunch of suspension things. But I know the starting isn't a clogged filter issue.

[SmokeE30]

tank or guage cluster could have been replaced but i belive the 62l should be correct for that car.

all that you need to undo in the rear is the lower shock mount bolt and the swaybar mount bolt to get the trailing arm to drop down, then get a big prybar under the spring and pop it over the knob it sits on and pull it out, just did both sides of my car in about 30 mins.

charcoal filter is located in the engine bay on the drivers side mounted low around the shock tower area.

[jeffnhiscars]

All of this seems to be based on the assumption that the gauge is accurate. They often aren't.

[bmwstephen]

i have the same issue. I just assumed thats how it was for us late model cars as we utilize a single pump and some sophisticated tubing to syphon from one end of the tank to the other

[Classiks]

While under the car doing my rear suspension today, I actually did notice my tank was dented in on the drivers side. I don't think that would reduce my fuel capacity by 20 litres though.

Jeffnhiscars: I'm assuming the gauge is accurate because if it were not then I'd only be getting around 360 km to a tank of 62 litres. This is not how much mileage these cars get. When the gauge is near empty, when I go to pump to fill up, the pump stops at around 40 litres every time. It never says 60 or 55 or anywhere close to what the tank can hold.

I will check my lines going to the charcoal filter and the filter itself. Thanks again everyone. If that's all good then perhaps killacam is right and a punched in gas tank reduces the amount of fuel it can hold by a lot, it is punched in where the fuel filler hose goes into the tank so since it's concaving there it may push the fuel up.

[blkbma]

Sending unit out of whack?

[jeffnhiscars]

... late model cars as we utilize a single pump and some sophisticated tubing to syphon from one end of the tank to the other

I'm quite sure that the pump does not move fuel from one side of the tank to the other on any e30

Jeffnhiscars: I'm assuming the gauge is accurate because if it were not then I'd only be getting around 360 km to a tank of 62 litres. This is not how much mileage these cars get. When the gauge is near empty, when I go to pump to fill up, the pump stops at around 40 litres every time. It never says 60 or 55 or anywhere close to what the tank can hold.

A fuel gauge is simply useless for calculating consumption so I encourage you to eliminate it from your thought process before it drives you nuts. Fill the tank, reset the trip meter, run the tank down, fill it again then divide it out. To be more accurate do this over a few fillups.

I really think anything else is a waste of time and energy.