Reference Sensor gap
#33
Thread Starter
I haddah Google dat
Rennlist Member
Rennlist Member
Joined: Nov 2008
Posts: 11,501
Likes: 4
From: Fresno, CA
"Could there be onboard memory processing that causes this?"
Remember, the fuel pump relay is not only energized once the speed/ref signal occurs,
but also when the #50 from the ignition switch/starter solenoid applies power to pin 4
of the DME ECM. Any signal noise or a poor ground on pin 4 will cause the fuel pump
relay to energize, thus running the fuel pump. A voltage as low as 4 volts on pin 4
will cause the fuel pump to 'run'.
Remember, the fuel pump relay is not only energized once the speed/ref signal occurs,
but also when the #50 from the ignition switch/starter solenoid applies power to pin 4
of the DME ECM. Any signal noise or a poor ground on pin 4 will cause the fuel pump
relay to energize, thus running the fuel pump. A voltage as low as 4 volts on pin 4
will cause the fuel pump to 'run'.
I had previously "fooled" the DME by pulsing the ref sensor against the fender, which is why I'm wondering if the stored logic was in run mode, not shut down mode. The car was running with no signal whatsoever from the reference sensor at the time power was last cut at the switch. Surely not all processing is done in real time continuously. That would be too much. There must be memory of some sort in the dme brain.
It's an interesting possibility anyway.