MS2 Not seeing RPM at startup intermittent
#21
So this weekend I did not have an issue starting it and running it. Turned it off 6 or 7 times always restarted. It started yesterday at lunch time. But this morning I get nothing. Again seems the problem is no cam signal. I was having a problem starting it on Friday but after re gaping the crank sensor and having it hooked to a battery charger I got it started. So I though it may of been a weak CCA on my battery. I have a smaller battery then stock. And every time I have an issue with it starting it seems the air temp and coolant temp are at there lowest. I dont know if it is a setting that may not let it see crank because of temperature? So this morning I tried switching the battery with another Miata battery i have and it still did not work. Then I tried jumping the car with another car and still no start. Do you have any idea where I should look next for diag?
#37
Boost Czar
iTrader: (62)
Join Date: May 2005
Location: Chantilly, VA
Posts: 79,729
Total Cats: 4,126
provides the 5v pull-up on your cam signal.
when the cam passing along the sensor it grounds the signal, and the MS can read that, but it has to drop to ground from voltage. if no voltage is provided on the cam signal, there's no difference between grounded and not grounded. so we apply a little voltage to the signal, so the MS can see it floating at 5v and then drop to 0v when it's grounded. whenever it sees that, it knows the cam made a rotation.
the crank sensor has a 12v pullup, but with your battery issue, the voltage may be dropping too low from 5v for the MS to pickup a signal from it...
when the cam passing along the sensor it grounds the signal, and the MS can read that, but it has to drop to ground from voltage. if no voltage is provided on the cam signal, there's no difference between grounded and not grounded. so we apply a little voltage to the signal, so the MS can see it floating at 5v and then drop to 0v when it's grounded. whenever it sees that, it knows the cam made a rotation.
the crank sensor has a 12v pullup, but with your battery issue, the voltage may be dropping too low from 5v for the MS to pickup a signal from it...
#39
I read this on the DIYPNP site
Cam Adjust: This lets you change the trigger voltage on the VR2 input. R20 increases the threshold trigger voltage, R21 decreases the threshold trigger voltage, and R39 can be adjusted to move it either way. If you already have information on what works for your sensors, solder a fixed resistor to either R21 or R20 as documentation recommends. For example, most Nippondenso ignitions work best with a 51K resistor in the R21 slot and R20 empty. If you’re having triggering problems and want to be able to adjust this yourself, leave R20 and R21 empty. Install R39 and adjust as needed to get a clean signal.
Do you think I could put a resistor in the R21 or would that make too much noise?
Cam Adjust: This lets you change the trigger voltage on the VR2 input. R20 increases the threshold trigger voltage, R21 decreases the threshold trigger voltage, and R39 can be adjusted to move it either way. If you already have information on what works for your sensors, solder a fixed resistor to either R21 or R20 as documentation recommends. For example, most Nippondenso ignitions work best with a 51K resistor in the R21 slot and R20 empty. If you’re having triggering problems and want to be able to adjust this yourself, leave R20 and R21 empty. Install R39 and adjust as needed to get a clean signal.
Do you think I could put a resistor in the R21 or would that make too much noise?