From digest.v6.n677 Tue May 20 12:29:25 1997
From: Richard Cartiledge <richard.cartledge_at_jigsawsystems.co.uk>
Date: 19 May 97 17:32:21 +0100
Subject: re><E28> L - Jetronic Question/problem
re><E28> L - Jetronic Question/problem
"Arthur Manowski" <manowski_at_space.net.au> wrote...
>I have a problem with my car that i think is related to the fuel injecti=
> Sometimes when I accelerate at low revs (about 2000rpm) the engine feel=
>strained/chocked and not much acceleration occurs. Sometimes it actuall=
>*slows* down. if i ease off the throttle the car seems to accelerate MO=
>than with a larger throttle setting.
This could be one of several things, as always.
- AIRFLOW METER When you open the throttle, you are opening the apertu=
re of the throotle butterfly, thus allowing more air into the engine. The=
airflow meter should measure the airflow and change the pulse-width of t=
he injector opening current - (opening duration) this duration is what c=
ontrols the mixture and gives the correct amount of fuel for the amount o=
f air coming in..
If the airflow meter is faulty, this may give a false impression to the i=
njection control unit and thus the mixture may lean out. Over 3500rpm wit=
h full throttle (as per throttle position switch), the L-jetronic system =
leaves the injectors open continuously, (you may notice a power band star=
ts here) this means that the airflow meter is ignored.
2. FUEL PRESSURE REGULATOR The fuel pressure at the injectors is desi=
gned to remain constant, the amount of fuel injected is controlled soley =
by the opening duration. The pressure regulator is located at the end of =
the fuel rail and returns excess fuel back to the tank to keep the pressu=
re constant. It controls the fuel pressure via a valve which is connected=
to a vacuum diagphram. The vacuum hose is connected to the bottom of the=
intake manifold. If you think about it, the fuel at the injectors needs =
to be about 3.0 bars of pressure, if the intake manifold becomes depressu=
rised to say 1.5 bars less than atmospheric pressure, this makes the pres=
sure across the injectors 4.5 bar instead of 3.0. If the regulator is fa=
ulty, it may be dropping the fuel pressure upon high induction.
3. You dont say which model you have, but you may wish to have the ignit=
ion timing checked, and make sure that the vacuum advance and centrifugal=
weights are working.
4. Also, the fuel pumps and fuel filter could be inefficient or clogged.
Hope it helps, Richard.
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