MSefi.com read only forum (Jan.15,2018)

This is sort of a loaded question. My question, does the solid, no PWM prime pulse occur for both injector banks? I found with my MSII v3, code version 2.92, TBI, 4 low impedance injectors, 2 and 2 alternating, that the prime pulse is a solid pulse for 4msec on one bank of 2 and the other bank has holding PWM only with no turn-on pulse, just PWM for the 4msec. I was using the prime pulse to troubleshoot the injector banks, and with one bank only PWMing, they won't fire. I have confirmed all circuitry is in working order with a scope. My only concern is getting this confirmed that what I see coming from the processor is correct.

Thanks,
Dan Williams
41 Willys Coupe
Chevy 454 w/6v71 blower 1:1
TBI injection w/Enderle Bug Catcher Injector Hat

Interesting question. Pretty sure I've seen both injector LEDs come on on my JimStim at switch on for the duration of the priming pulse. But haven't checked on the car.

Yup, same thing. The JimStim will show both injector banks firing at switch ON. But, one of the banks is PWMing, not ON constant during the prime pulse. I was using the prime pulse to diagnose one bank not firing. I spent 3 days trying to figure this out and finally I scoped it and saw what was happening. I was looking for squirt out of that bank and wasn't seeing it. I can see the fuel coming out since the injectors are on top of the blower.

I wonder if it's a firmware issue? Do I need to reflash the firmware and reload my parameters?

Even more interesting. Thinking about it, I'd sort of expect the MS to use PWM for the priming pulse if set for low impedance injectors and no series resistors. If it were 'pure 12v', the drivers would have to supply 20 amps each on this 8 cylinder engine.

Be interested to see the answer from one who knows.

Well, they state in the megamanual that for cranking, MS hits all the low impedance injectors with a solid pulse every tach pulse, so I expected the same for the prime pulse. The prime is only 4msec, so unless the 12v source impedance isn't the best, apparently MS should be able to so it. It's more of a curiosity now, since I got further into it and I'm firing all injectors properly during cranking. I have other issues I'm sorting out now. I guess it goes with the territory when designing your own induction system. Darn thing is that the setup was working for a good season before things hit the fan.
I blocked off 2 of the three butterflies on the injector hat so it makes the throttle more streetable, because that is my throttle body. One of the block off plates started to pull away from its spot, totally screwing up my tune. The car is strictly for cruising, so part throttle ease of driving is critical, and I'm purposely keeping the blower from developing boost. Guess I have to get the plate welded in rather then relying on JB Weld.

I am surprised that there isn't some sort of capacitance on the 12v injector supply line that would smooth out the pulses from such a high current hit. For my injectors, it's a 20 amp pulse on the line for prime and cranking. But it seems to work, only when all of my mechanical stuff is working though.