VB921, No Spark

[KaoticOrder]

Setup:
MSnS-Extra on a v3.0 board
DSM CAS modification (dual wheel cam angle sensor on back of head)
4cyl Mazda engine
2 coil wasted-spark setup driven by two VB921s


I believe that I have it correctly configured in MegaTune because when I try to crank it over the rpm is a little higher than expected but about right (around 400RPM). I'm getting a good reading from all of my sensors, as well. I am just not getting any spark. There are 3 wires going to the coil: 1. power for both 2. coil1 signal 3. coil 2 signal. My question is how do I test to make sure that the VB921s are working correctly (i.e. providing spark)? Also, will the gauge of wire affect whether or not the VB921s can get the correct amount of current to the coils? Any other clues or pointers in the right direction would be very welcome.


Thanks In Advance,
Stephen

[Toyshop.no]

Hi!
We have the same problem.
Two times the VB921 got loose from the main bord and was lying loose inside the cover. It had been so hot that it melted the plastic screw. Put it back on, and got sparks for a while, but then it died. Getting all the correct response from the hall sensor, fuel pump starts and injectors are triggered when i turn the distributor by hand out of the engine. Pretty sure we have done everything right, but something is responsible for this VB921 to get loose or die.

Would be very greatful for help!!

(sorry for my bad enlish, im Norwegian )

Howard Norheim
Toyshop.no

[KaoticOrder]

v3.0 MSnS-E running 24s13c
Megatune 2.25

Well, my problem amounted more to a fried I/O line on the processor than anything else. I swapped it out with a new one and everything sparked normally.

As for how the line got fried, I tried buying replacement transistors Q6 & Q8 for my board from RadioShack. I bought the wrong ones the first time around (they were the opposite of what they should have been i.e. PNP instead of NPN, or vice versa). Either way, problem solved.

[jsmcortina]

Hi!
We have the same problem.
Two times the VB921 got loose from the main bord and was lying loose inside the cover. It had been so hot that it melted the plastic screw.

Check your dwell settings and ensure you have "spark output inverted". If possible wire your ignition coils from the fuel pump relay so they cannot get power until the Megasquirt is ready.

James

[purple people eater]

i have had trouble with the vb921 getting very hot if my dwell settings are wrong, and yes spark output must be inverted or it really cooks