Recent black smoke and fuel smell

  • 1996 BMW 328XI
  • 2.8L
  • 6 CYL
  • 2WD
  • 150,000 MILES
Firstly the car was running beautifully until recently it had a slight dead spot on idle or on take off, the idle would decrease on its own and there's always black smoke and fuel fumes.
I am guessing it's over fueling, however I can't seem to find the source of the problem.
I've already replaced the airflow sensor sorry hoping it would help would the de-fluctuating in the idle.
Unfortunately they didn't help.
I've also had the valve stem seals checked. It isn't that as well.
This one really beats me. Can you guys help?
Do you
have the same problem?
Thursday, March 14th, 2019 AT 4:43 PM

1 Reply

Hi and thanks for using 2CarPros.

If you are getting black smoke from the exhaust, the engine is getting too much gas. What I recommend starting with is a fuel pressure and pressure regulator test. Here is a link that shows in general how one is performed:

Here are the directions, pressure specifications, and pics specific to your vehicle for checking.


Checking fuel pump delivery pressure (M52, M52TU)

Turn off ignition.

Picture 1

The fuel in the fuel lines is under pressure (approx. 3 bar)!

Catch and dispose of escaping fuel.

Picture 2

Prepare special tool kit 13 5 220 (consisting of 13 5 221 and 13 5 222).
Connect special tool kit 13 5 220 to pressure sensor of DIS Tester.

Picture 3

Remove dust cap (1) from measuring valve on fuel rail.

Picture 4

Unscrew check valve (1) on special tool so that valve remains closed in fuel rail.
Attach special tool kit 13 5 220 to fuel rail and tighten down firmly so that sealing ring in special tool is sealed.

Picture 5

Start engine.
Screw in check valve (1) on special tool until a pressure reading is displayed at DIS Tester.

Do not under any circumstances screw in the check valve up to the mechanical stop. This could damage the measuring valve in the fuel rail.

Picture 6

Measuring fuel pressure:
- Select measuring option.
- Multimeter function appears.
- Select pressure test.
- Read off pressure.

Test pressure,
refer to Technical Data.
Injectors And Lines, Fuel Pressure Regulator M52

Picture 7

Switch off engine.

Picture 8

Checking fuel pump:
Detach fuel pump relay (2).

Picture 9

Remove fuel pump relay,

Picture 10

Remove fuel pump relay,

Picture 10

Connect up special tool 61 3 050 to terminal 87b and terminal 30.
Operate button for approx. 10 sec and read off delivery pressure at DIS Tester.

Picture 12

Removing special tool kit 13 5 220:
- Switch off engine.
- Screw out check valve again fully.
- Remove special tool kit 13 5 220 from pressure regulator housing.
- Catch and dispose of escaping fuel.

Interrogate fault memory of DME control unit. Check stored fault messages. Rectify faults. Now clear the fault memory.


If you are getting black smoke, the fuel mixture is too rich. My first suspect is a bad fuel pressure regulator. Try these directions and let me know the results. Keep in mind, pay attention to how quickly fuel pressure drops when you turn the pump off. If it drops quickly, you may have an injector leaking.

Take care,
Was this
Thursday, March 14th, 2019 AT 6:10 PM

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