Fuel pump PWM control... fuel pump relay output function?

[OkayDriver]

I'm in the process of wiring my car up for a PWM controlled fuel pump (open loop) with a MS3-Pro. My understanding is that this overrides the default behavior of the fuel pump relay output even if a different output is chosen for PWM control of the fuel pump. This seems to be in conflict with the recommendation that all other engine related devices be powered up when the fuel pump relay output is active so that they are powered up when the engine is cranked and then are turned off when the engine stalls.

In this scenario what is the best practice to allow the MS3-Pro to control the relay powering the FPDM, lift pump, wideband o2 sensor, fuel injectors, coils, etc?

Thanks.

[Matt Cramer]

If you set the output to the fuel pump pin, it will use PWM on the regular fuel pump relay output.

If you select a different output pin in current firmware, the regular fuel pump relay output will operate as normal.

[OkayDriver]

That is great to hear Matt. I had the impression from searching old threads that the normal operation of the fuel pump pin output was overridden no matter what output was chosen for PWM . Maybe it was that way in the past.

I glanced through some of the source code to try and figure it out myself but didn't have much luck locating the section that deals with that. It will take a bit of studying to figure out what is going on inside there.

Thanks again.

[darthmayndawg]

I do not want to sound redundant. But ..
MS3x SBF says Purple Wire out to Fuel Pump Relay. Are you saying I need to verify that that is the setting ? Even though that's the normal setting

[Matt Cramer]

I do not want to sound redundant. But ..
MS3x SBF says Purple Wire out to Fuel Pump Relay. Are you saying I need to verify that that is the setting ? Even though that's the normal setting

The MS3X always uses pin 37 of the main board connector as the fuel pump relay output, or as the main fuel pump relay output if you have enabled a secondary PWM fuel pump control output.

[darthmayndawg]

Thanks Matt I am aware of my mistake now. Also James corrected me and I have to adjust.

[darthmayndawg]

Wired it correctly and now FP works when Test Mode enabled. IDK about the prime pulse though.