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Warm starting problem (look

                       Subject:                               Time:10:06 AM
  OFFICE MEMO          Warm starting problem (look for fuel...  Date:8/28/96

  I encountered the same problem after an engine rebuild/swap job on my 79
528i.  The car refuses to start unless you crank the engine for several
seconds, or several times after the car has been driven and then sit for about
an hour.
   Based on suggestions from friends on the digest, I first try to isolate
problem to the pump check valve.  I use a air hose clamping device to clamp
the incoming fuel line from the fuel pump.  (A locking vise grip will do
nicely, just make sure you do not apply too much clamping force and use some
rags to wrap the fuel line to protect it from the jaws of the vise grip).  You
can do this right after you stop the engine.  After you wait for an hour or
so, remove the clamping device and start the car.  If you can start right
away, there is a good chance that the fuel pump check valve is defective.
******Remember to remove the clamping device before starting the car,
otherwise your fuel pump will try to pump the fuel to nearly 100 psi!! ******
    You can use the same technique to clamp the fuel line to the cold start
valve, making sure it is not leaking!
    You can also clamp the return fuel line after the fuel pressure regulator,
check to see if it is leaking.
    It is even better if you can connect a fuel pressure guage so that you can
see the fuel pressure state during the diagnostic procedures.
    In my case, however, none of the above was the cause.  Ultimately I
tracked down to 3 leaky fuel injectors.  So, more than just loosing fuel
pressure, the engine has been flooded at the same time.  Based on the fuel
pressure guage indications, the main fuel pump can pressurize the fuel rail in
a few seconds.  I feeling is the warm start problem may be caused primarily by
the flooding, at least in my case.


Eric Huang