Ignition and it's relation to fuel pump triggering - safety

[Tony Hoffman]

Here's how it works.
 
The ECU gets a signal from the hall sensor and the two reference sensors. Not sure if all three are required for the FP relay to be triggered, but they are all required for the ignition system to fire. Anyhow, if the engine dies for any reason, the signal dies with it. Then, the ECU quits triggering the FP relay. So, if you flip a car, and the engine stays running (usually not for long) the FP relay stays energized. If the car dies, the FP relay opens. That's how Bosch did their safety. If, for example, you broke a fuel line in a crash, the engine would die for obvious reasons. Then, your FP relay would also shut off the pump, greatly decreasing the chance for a fire.
 
Tony Hoffman 

Kent McLean <kentmclean at mindspring.com> wrote:
Brett Dikeman wrote:
>> (for safety reasons; if the car overturns, the FPR opens
> 
> Where are you getting this information from?

Probably mis-remembered from a number of sources.



Ah, here's a good one:


It seems some fuel pressure relays have a switch, but apparently
the Bosch ones do not. I stand corrected.

So is the FPR's only function to make sure the engine is cranking
over and/or running before it will provide juice to the fuel pump?


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