Jay, you mentioned the active eletronics inside the Hamlin sensor.
What are the chances that it's compensating for the missing tooth?? I noticed on my scope trace that the missing tooth did not seem like a complete missing tooth. Double check that you are getting the proper gap for the missing tooth please. This has been driving me nuts!
Also, huber mentioned that he had problems once with a tachometer that seemed to be loading the Tach Output too much, and it behaved similarly. For grins, maybe disconnect the Aeromotive pump controller's tach interface and see if it changes anything? Might need a stronger pullup on the tach output...
More info on this issue. I think the problem is the Aeromotive fuel pump controller, not the ems-pro. I hooked the scope up to the Hamlin sensor and watched the signal while I was cranking the engine. The signal was stable during the entire cranking period, and I was able to watch the fuel pressure gauge go back to zero after a few seconds, while the crank sensor signal still looked fine.
Next I monitored the voltage on the control wire from the ems-pro, that energizes the fuel pump relay. During cranking this voltage pulls low to turn on the fuel pump relay. During cranking the voltage on this wire stayed low the whole time, even though the fuel pump shut off after a few seconds. So, the ems-pro is seeing the signal from the crank sensor, and is trying to keep the fuel pump running, but the Aeromotive fuel pump control box is turning off the pump after a few seconds.
When using a carbed setup, the Aeromotive fuel pump controller turns the pump on for a few seconds at key-on, and then shuts off, waiting for an RPM signal before it turns the pump on again. It also runs the pump at a reduced speed when the engine RPM is below 3000 or so, to save wear and tear on the pump. There is an override switch on the dash, connected to the fuel pump controller, that makes the pump run continuously if desired.
I think what is happening is that at key-on, the ems-pro is turning on the fuel pump relay to charge the fuel lines, and then shutting off the relay waiting for an RPM signal. When the fuel pump relay turns on, the Aeromotive fuel pump controller does the same thing, turning on the fuel pump to charge the fuel lines for a few seconds, and then shutting off. Either the ems-pro or the Aeromotive controller is shutting off the pump after a few seconds, but in any case if the key is turned on and the engine isn't cranked the fuel pump runs for a few seconds, then shuts off.
Then, when the key is turned to crank, this whole cycle repeats. However, based on my tests, when the engine starts cranking, the ems-pro sees the signal, turns on the fuel pump relay, and keeps it on. But the Aeromotive fuel pump controller is not seeing the RPM signal, so it turns on and goes through its charge the fuel line cycle of 3-4 seconds, then shuts off.
The tachout signal from the ems-pro goes three places: to the Autometer tach, to the Innovate Motorsports DL-32 datalogger, and to the Aeromotive fuel pump controller. You may be correct that the ems-pro's tachout signal can't drive all three of these devices, at least not until the engine starts. The tachometer in the car does work fine, but I haven't tested the DL-32 yet so I can't say about that one. I can say that when the engine is running, the Aeromotive fuel pump controller is definitely seeing the tach signal, because you can tell by watching the fuel pressure gauge. When the pump controller is limiting voltage to the pump, the fuel pressure bounces rapidly between 20 and 30 psi, but when the fuel pump controller's override switch is flipped, the fuel pressure goes right back up to the stable 45 psi level. I'm kind of wondering about this, since it will obviously affect the A/F ratio with the car running down the road, and also at idle. I noticed during Drag Week that if I tuned the idle with the fuel pump override switch flipped on, when I flipped it back to turn off the override the car would nearly quit. Less fuel pressure, less fuel at idle.
In any case, I think its much more likely that the slow RPM signal during cranking is not being picked up by the Aeromotive fuel pump controller, and so it thinks the engine is turned off, and won't turn on the fuel pump. I thought an easy fix for this would be to just flip on the override switch during cranking, but it won't work; the pump stays off during cranking even with the override switch flipped on.
I need to do some investigating on this, including reading all the literature on the Aeromotive fuel pump controller, and also looking at the tach signal going into the controller with the oscilloscope. I'll post what I find out when I have something definitive...
EDIT: Looks like I spoke too soon; now I am seeing the ems-pro fuel pump turn-on signal dropping out when the engine is cranking. Hmmm, back to square 1...
