ultimatepoghero Posted May 22, 2007 Share Posted May 22, 2007 how would i know if my vb921 high current ign driver is burned out. i haven't been getting rpm signal one day suddenly and i haven't been able to figure out what went wrong seems like this is the last thing i could think to check. Quote Link to comment Share on other sites More sharing options...
big-phil Posted May 22, 2007 Share Posted May 22, 2007 Mine went out but I still had an RPM signal. It could be your optical sensor inside the stock 83 280zx turbo dizzy. A new vb921 is about $5.00 from diyautotune.com so you could buy one, put it in, and see if that works???? Quote Link to comment Share on other sites More sharing options...
Matt Cramer Posted May 23, 2007 Share Posted May 23, 2007 Megasquirt is going to need an RPM signal before it will trigger the VB921. Is it the Megasquirt that can't see RPM, or the tach? Quote Link to comment Share on other sites More sharing options...
ultimatepoghero Posted May 23, 2007 Author Share Posted May 23, 2007 the megasquirt doesn't show rpm neither does the tach. About the optical sensor though i thought about this as a problem and i swapped it out with the original 300zx sensor and wheel because they used to work and that CAS is actually brand new, it was a shame i blew like a $100 after realizing i needed to use a 280 CAS and Opti-wheel. Still no rpm signal. This all happened after a trip out of town to jacksonville, FL about an hour away. the car did great the way down but wouldn't crank when i went to leave the first place I stopped in town. after five min or so it did and drove around town and almost back home when it started misfiring a lot progressively worse and worse until it cut off. I let it sit for about an hour took the dizzy apart the CAS was pretty warm don't know if it was abnormal but after everything cooled down i put it back together and it cranked right up and i took it home. I drove it a few more times before it did the same thing again except this time it's not going to fix it's self haha. Seems to me like something is loose maybe or a part somewhere is giving out or burning up perhaps. I was playing around with the 2 CAS's i have checking the prongs with a multimeter meter and the 2 pins closest to the middle shows no continuity on the old 280 CAS but does on the Brand new 300 CAS. Seems like i did this before and didn't find a difference like this, so i thought maybe the 280 CAS was broken. Seems to me though if that was the case it would have worked when i swapped it with the original stuff because it would crank and run like that before just not well because of the 300 optical wheel having one big slit and five little ones. Originally i tried to use the 280 opti-wheel and the 300z CAS because it was new but it wouldn't give me rpm signal i had to use the one from the 280 luckily it all fit. One last thing to i only use one pull up resistor in my setup one the cas line before it goes to the megasquirt could this be causing problems? Quote Link to comment Share on other sites More sharing options...
big-phil Posted May 23, 2007 Share Posted May 23, 2007 I also had trouble with the plug on the bottom of the dizzy. My car would just die when you closed the hood? Found out that the hood hinge was pushing on my intercooler pipe, which pushed on the plug harness that went to the dizzy. It had cracked wires. I did away with the plug, rewired it and it works fine. Like Matt (who IS the man by the way) said, if megatune, and your tach are not seeing an RPM signal, neither is the vb921. I only burned mine up after setting my dwell way way way too high! I had no spark, but megatune still could see RPM when cranking the car. Here is kinda how to replace it by the way. and what sounds to be the same problem you are having? Its a small world. Thats me in the video by the way. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 24, 2007 Share Posted May 24, 2007 So there are a couple of ways to burn out the VB921. 1) Not choosing GOING HIGH INVERTED in megatune. 2) Using too much dwell. I will try to learn from your mistakes....I am going to fire it up this weekend for the first time with the MS-II. Quote Link to comment Share on other sites More sharing options...
big-phil Posted May 24, 2007 Share Posted May 24, 2007 So there are a couple of ways to burn out the VB921. 1) Not choosing GOING HIGH INVERTED in megatune. 2) Using too much dwell. I will try to learn from your mistakes....I am going to fire it up this weekend for the first time with the MS-II. Good luck!!!! Quote Link to comment Share on other sites More sharing options...
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