Hello everyone! I submitted a problem several months ago and this forum provided me with the solution.... a solution I would have NEVER figured out on my own! Many thanks!
Here's another problem that I hope will meet with similarly good results.
I am using a megasquirt 2 on a 4.0 Liter Range Rover v8. I can start the motor with a little starting fluid sprayed into the throttle body. Once the motor is running it runs great. I've been driving around with the Tuner Studio "autotune" feature on so the computer's been adjusting my tables nicely. It just won't start without the starting fluid sprayed in. Ordinarily I'd suspect a fuel problem but I've got the cranking fuel settings quite high. I've lowered the "cranking rpm" to 100 because as I'm cranking the engine the RPM maxes at 170 and only reaches that high rarely. Most of the time the RPM reads zero and occasionally jumps to 60-90 RPM.
The "cranking RPM" number really means the threshold below which Megasquirt considers your engine to be cranking, and uses all the relevant settings, and above which the engine is considered to be running and uses the "running" settings.
Based on what you wrote, I'd set cranking RPM to 250 or maybe 300, you want it to be *above* the actual cranking RPM.
Eric Law
1990 Audi 80 quattro with AAN turbo engine: happily running on MS3+MS3X
2012 Audi A4 quattro, desperately in need of tweaking
Actually I just read your post a little more carefully and think you have two problems. The cranking RPM is one.
But during cranking, the RPM should *never* read zero! It should read the actual speed the engine is turning. It sounds like you may have a triggering problem where at low cranking RPM, the Megasquirt isn't seeing the output from the sensor(s) providing the RPM signal.
Are you by chance using a VR sensor on the crankshaft? If so, you might need to adjust the "VR pots" on the Megasquirt mainboard. You can look in the online manuals for the procedure.
Eric Law
1990 Audi 80 quattro with AAN turbo engine: happily running on MS3+MS3X
2012 Audi A4 quattro, desperately in need of tweaking
Yes, I am using the stock VR sensor and toothed wheel from the range rover motor. My earlier problem was misfiring and unstable idle that was fixed by inserting a resistor in-line from the crank sensor. At that time another moderator mentioned I might need to adjust the VR pots but I never did because it ran fine (once started) without the adjustment. Perhaps I should see if adjusting can solve my starting problem without interfering with the idle.
By the way.
I had a similair issue with e VR detection of the MS: It was not able to read the signal of the VR sensor below a specific RPM.
Worked fine at summer but at winter days no chance to get the car running. That's the tricky thing at VR sensors: The lower the RPM, the lower the voltage coming out of the sensor. I lowered the sensor gap etc but no luck.
Finally, I got a VR detection circuit based on the fabulous MAX 9926 chip like Jean offers them at jbperf.com (http://forum.jbperf.com/viewtopic.php?f=6&t=78).
I must say, I am really impressed. Very resistant against noise and able to read very (very) low RPMs.
If you still get sync loss issues during cranking, you can separate the VR- in signal from the MS ground (if you want to do this mod in combination with the stock VR detection circuit of the MS look at "common mode rejection) at http://www.megamanual.com/ms2/vradjust.htm )
Thomas
SUCCESS !!! Opened up the box, located a tiny screwdriver, rotated the pots counterclockwise as engine cranked until rpm signal registered consistently .... and voila .... engine started right up! Boxed everything back up and connected all the wires, turned the key ... again started right up! Took it out for a drive, got engine to 180 degrees, stopped engine, waited for several minutes to maximize the heat sync, turned the key .... again started right up!!!
