Question

I have a fuel vapor leak in a ’94 318ic I can’t seem to get rid of.
Here’s what I’ve done:

Replaced the fuel pump and tank seal

Replaced the charcoal canister and valve

Replaced the fuel filter

Replaced the fuel lines on top of the engine block, underneath the manifold.

Replaced the tank cap.

Performed a system smoke check (negative).

There is no smell inside the car, which eliminates a cracked tank, I believe.

The garage reeks of raw fuel odor when the car is parked in a closed garage, otherwise, you can’t tell there’s a problem. The problem is constant (in the garage), meaning there is no difference if the car has been run recently (pressurizing the fuel system) or has been sitting idle for days.

One friend mentioned fuel injector rail or the fuel injector O-ring, but I think the problem would go away after the car sat for several days?

Any ideas?

Answer

Hello Mr. Garvey,

I do have a few questions for you.

First question, when you performed the smoke test was the valve open or closed ?
Is the check engine light on?

The computer is very good at measuring EVAP system leaks and if there was one chances are the light will be on.

The car also has a saddle style fuel tank, that means that it has 2 fuel level senders, one with the pump and one by itself on the other side of the tank, consequently there are 2 seals at the top of the tank, I’m not sure if you replaced one seal or both.

Does the fuel level affect the issue at all?
And how does the car run?

I would suspect a leak on the outside of the car, the best way to figure out where is to place a piece of clean cardboard under the car, if any fuel leaks it will evaporate but leave behind a stain.

The other possibilities are the fuel pressure regulator leaking, to check that remove the vacuum hose at the regulator, if you see fuel it is bad.

Is the car hard to start after it sits for a while?

If there is a leak it should lose fuel pressure over time which will cause an extended crank symptom. Fuel injectors that are leaking outside will leave a stain at the leak site, clean the engine and keep an eye on it. Please let me know a little more and we will narrow this issue down to the cause.

Please reply to the questions in blue italics so I can help you further.

Thank you for the question.

Gil Neves

Florida SunCoast says:
August 26, 2017 at 1:04 pm
Answers in RED above.
Also, besides me, I’ve had two BMW shops look at (and work on) the car. Although many of these replaced parts were original, I’m still spending time and money on fixes that are not working so far. I have also aired out the garage, then closed it up and tried to “sniff-out” where the vapor leak is emanating from – no luck. The line(s) from the tank to the firewall area appear dry. The only other area I – or others – have not investigated is the filler neck below the rubber gasket inside the filler door. I have tried three different gas caps – so negative on the “easy” fix.
Reply
1. Florida SunCoast says:
  August 29, 2017 at 8:19 am
  Hello Mr, Garvey.
  If the system was checked with a smoke machine I would discount the filler hose and all of the EVAP system as a leak would have shown with the smoke test. It sounds like you should have the smoke test done again, if there was a liquid leak chances are the car would be hard to start after it sat for a while and the gas mileage would suffer, maybe something was missed during the first test. The leak at the fuel pressure regulator would also cause a running issue.
  Thank you.
  Gil Neves
  Reply