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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 3 Series / 4 Series > E30 (1982 - 1993)

E30 (1982 - 1993)
God's Chariot. The E30 was produced primarily from 1982 through 1991. The cabriolet was the one exception which was produced through 1993.

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  #1  
Old 06-28-2014, 07:02 AM
bmwe30man6293 bmwe30man6293 is offline
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Location: Gold Coast, Qld.
 
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Fuel Pump not priming!!!

Can someone please tell me if the fuel pump on a 1989 318i is supposed to prime before the engine starts, and if so what is the feedback mechanism to shut it off, once primed??
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  #2  
Old 06-28-2014, 09:34 AM
Dromey Dromey is offline
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Location: Provo, UT
 
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Mein Auto: '90 325iC
My fuel pump on my 325i only turns on when the motor is cranking, it doesn't prime beforehand.


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Old 06-29-2014, 12:13 AM
Billwill Billwill is offline
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Mein Auto: BMW E30 318i 1991
Quote:
Originally Posted by bmwe30man6293 View Post
Can someone please tell me if the fuel pump on a 1989 318i is supposed to prime before the engine starts, and if so what is the feedback mechanism to shut it off, once primed??

The fuel pump does not run until the engine has started. The pin 86 on the fuel pump relay coil will get +12 volts on pin 86 at all times while the other side of the relay coil...pin 85...gets Ground from the ECU once the engine starts to turn over and the ECU picks up the Crankshaft Pulse Sensor pulse.

The fuel pump then runs all the time until you switch off the ignition and the ECU drops Ground to the relay...there is a fuel-return line that sends unused fuel back to the tank as measured by the Fuel Pressure Regulator.
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Old 06-29-2014, 12:42 AM
bmwe30man6293 bmwe30man6293 is offline
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Thanks guys
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  #5  
Old 06-29-2014, 05:43 AM
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downhiller downhiller is offline
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do you have to crank the engine awhile before it starts?


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Old 06-30-2014, 12:39 AM
Billwill Billwill is offline
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do you have to crank the engine awhile before it starts?


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No, there should be pressure maintained in the fuel rail overnight by the fuel regulator so the injectors should start pumping as soon as the engine starts to turn over.
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Old 06-30-2014, 04:46 PM
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downhiller downhiller is offline
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Originally Posted by Billwill View Post
No, there should be pressure maintained in the fuel rail overnight by the fuel regulator so the injectors should start pumping as soon as the engine starts to turn over.

i only ask asked cause most times when people ask this is it takes a bit to start. and if if takes a few seconds of cranking to start theres a leak in the fuel system somewhere and allows the fuel to be pulled back to the tank. i forgot if mine was a fuel pump or an o-ring on a injector. either way took me about a week to figure out by accident.


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Old 06-30-2014, 08:51 PM
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BMWFatherFigure BMWFatherFigure is offline
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Mein Auto: E23;E30;E38;E32;E34 +
No more than 4 compressions before it catches. More than that needs investigation.
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