RE: E30 325i hard to start when warm

[Chris Pawlowicz <cpawlowicz@xxxxxxxx>]

> "Allan Williams" <allanw@domain.elided> asks
> > 
> > We have a 1990 325i SE, and it has this small problem-
> > 
> > If you drive it until it is fully warm, then shut it off for 
> > 20+ minutes, it is hard to start. It cranks and cranks, but 
> > doesn't fire. If you hit the gas it will sometimes start,..snip
> 

Alex sez
> Allan,
>         That is a hint to go on. 
>         By hitting the gas pedal you open the throttle and let more air in.
> The only time this would help is if the initial fuel/air mixture was too
> rich...snip 

I was talking to a BMW mechanic in the fall and he was telling me why
later E30 325i
very often have warm start problems..

I think he said it was because the sensor which figures out crank
position (mounted on the
 front of the engine, unlike earlier E30s with the sensor on the
flywheel) tends to get
a bit flaky when really hot

cold engine - sensor works fine because it is cold
warm engine/stopped - heat soak makes sensor malfunction *until* the fan
turns enough to blow
 cool air over the sensor and cool it down a bit
hot start - sensor has not had time to heat up yet and works fine

New sensors work a bit better, but 'they all do that' (later E30) to
some degree


Chris Pawlowicz
'89 325i
'74 2002

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