MSII + V2 board + VB921 + 8 pin HEI. Spark issues - FIXED

460stang · Post by **460stang** » Tue Aug 01, 2006 11:01 pm

We are trying to use a VB921 and just get a RPM signal from the 8 pin HEI.

With the proper purple with white wire from the 8 pin HEI the MS gets no crank signal.

Using the White wire from the HEI and running it straight to the coil it runs fine (HEI limp home mode 10 deg) and then using the coil negative as the trigger source it runs the MS and all is good, just no timing control.

Seeing as I just need a good input from the HEI module I ran the white wire to the MS and the VB921 to the coil negative. It will not run this way UNLESS I put a test light on the circuit HEI to MS RPM input signal as a pull up resistor, and then runs, but poorly with a very erratic timing signal.

So I am assuming that the V3.0 board has the right signal conditioning for this but the V2 board does not. I thought the 8 pin HEI would properly condition the signal, but I guess not.

The question is do I have to recreate the whole VR input signal to get the white or purple with white HEI wires to give me a dependable RPM signal?

Or what would be the best way?

Thanks.

460stang · Post by **460stang** » Tue Aug 01, 2006 11:35 pm

This is what I found to make HEI work with V2 board and MSI chip. I know part of this is for the timing control part, but is something like this required to make the HEI module RPM signal acceptable to the MSII chip as well?

.Remove D5,D8,R10
.Remove jumper between XG1-XG2
.Fit wire between XG1 and right of D5 (non band)
.Fit wire between bottom of R10 and small hole above D9 (this is a +5v source - you could also use the hole to the left of D4)
.Fit 1.3k resistor in place of D8 (1k-2k ok)
Add 1k resistor from (-) of D17 to the right (5v) side of R23
Run a length of wire from D17 (-) to X12

460stang · Post by **460stang** » Wed Aug 02, 2006 3:58 pm

I put the MSII chip on my buddies V3 board and set the jumpers for opto in and it runs fine using the correct RPM input from the 8 pin module (pin R purple w/white).

Do I need to recreate the complete V3 hall circuit to get the V2 board to work with the MSII chip?

460stang · Post by **460stang** » Thu Aug 03, 2006 10:48 am

Thanks Lance

I did the above and went through the V2 and V3 schamatics and can find no differences now.

The trouble is the V2 MS does not work on the truck. Works fine on the stim but not the truck.

The V3.0 MS does work on the vehicle. We are using the same MSII chip in both the V2 and V3.

Any ideas?

Thanks.

460stang · Post by **460stang** » Thu Aug 03, 2006 4:04 pm

WE did the MSnSE mod to the V2 board (the one where the module grounds the circuit instead of supplies 5 volts).

We still have no RPM input. Now it no longer has RPM pulse on the stim as well.

Is the stim still supposed to work with this mod or did I screw up the mod?

Dang....

Any help would be appreciatted.

Thanks.

460stang · Post by **460stang** » Thu Aug 03, 2006 5:02 pm

Ok so we scoped the Pin 14 on the MSII chip with both boards.

With the V2 board we get a clean square wave but it only goes 3 to 5 volt.

With the V3 board we get zero to 5 volt.

Something wrong with the optoisolator or the ground supply to it?

Seems odd as this ran as a fuel only V2 for a couple of years with no issues before the MSII update.

460stang · Post by **460stang** » Thu Aug 03, 2006 11:05 pm

OK it seems to be working now.

One of the mods to the V2 board (in what was called the "MSnSE mod" ) was to put a 1.3K resistor in place of D8. For us this resistor value was to high and the 8 pin HEI module was unable to pull the 5 volts low enough to trigger. We had a 2K pot there set at the 1.3K, we trimed it back to .7K, it seems to tigger clean there.

I still don't know why the orignal setup (with the mods lance suggested) did not work. To look at it seems just like what was working with the V3 board.

Anyhow It runs, not taking it apart to figure out if we can get it to run the other way.

PSIG · Post by **PSIG** » Fri Aug 04, 2006 9:49 am

Just as an FYI for future reference, the VR INput (not opto/Hall circuit) on the v3 board reads the GM 8-Pin signal just fine.

David

460stang · Post by **460stang** » Fri Aug 04, 2006 8:15 pm

Yea if I was doing a V3 install I would use the VR in for sure. In this case the V3 was just used to make sure it worked. The point was to get the V2 board working.

PSIG · Post by **PSIG** » Sat Aug 05, 2006 2:38 pm

460stang wrote:Yea if I was doing a V3 install I would use the VR in for sure. In this case the V3 was just used to make sure it worked. The point was to get the V2 board working.

I understand. I was inserting that verification comment for future researchers that may check this thread to solve a similar problem.