Fuel Pump operation on E12
* Subject: Fuel Pump operation on E12
* From: Sergio Juan <juans_at_setpoint.com>
* Date: Wed, 28 Aug 96 11:34:12 -0500
>> About hard starting due to lack of fuel pressure when the engine is cranked
because the fuel pump
doesn't begin to function until the engine begins to crank...
Eric Tangen wrote:
> The pump operates: 1. while the starter is cranking & 2. when the flap inside
the air flow meter
moves >off the fully closed position (there is a reed switch under the plastic
cap on the AFM that
>You can turn the fuel pump on by putting the ignition key to the 'on' position
and lodging the air
flow >meter door open, all without having the engine run.
I have an 86 VW Scirocco which had a fuel pump relay that ran the fuel pump f
or one second when
the key was on 'ON' position/cranking position (by the time you got to the turn
ing the engine, the
pressue in the fuel system was already built. When that relay went out, I got
an aftermarket one
and this one only runs the fuel pump when the starter is cranking or engine is
running (no priming).
The car seems to take more cranks to start now...
One suggestion earlier (from Douglas Wyman) was to add a check valve before the
fuel pump, because
the one built in the pump may be leaking, to prevent losing presure. Apparentl
y this works well...
My question: Is is possible to get a fuel pump relay (or other solution) for t
he E12 that will
prime the fuel lines (run the pump for a second) so the system is already press
urized when the
engine begins to crank?
'79 528i 180k...
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