7 pin HEI and MSD 6A misfire

Ron Foster · Post by **Ron Foster** » Thu Mar 23, 2006 10:38 am

Hello,
I am setting this up on a TPI turbo SBC. I have an MSII 3.0 runing 2.1 firmware and megatune 747 ( I think). Currently I have the MSD hooked up on the stock location coil side of the 7 pin and using the MSII to control timing( this is the way it was hooked up with the stock ecu as well) I have all of my settings configured to match the 7 pin and a 3.5ms dwell. I have been getting a miss at idle and at 2000 RPM's the tack will spike and misfire and drop to 1800. Is there a better way to have hooked this up or is there a different configuration I should use?

Thanks

krisr · Post by **krisr** » Thu Mar 23, 2006 3:21 pm

When I had HEI7pin and MSD6AL working together, I had the white wire connected to the C pin and set max spark dwell and duration to 25.5. This requires a modification to the .ini file in Megatune (see the docs for which variable).

Also make sure your distributor wiring to HEI is correct. I had to reverse my MSD distributor wiring for HEI

It worked flawlessly.

Ron Foster · Post by **Ron Foster** » Fri Mar 24, 2006 5:03 pm

Yes, I checked the wiring and it apears to be correct, the white wire is on the c term of the ignition module.I found the docs on the ini file and changed it in the note pad in the doucuments. I tryed to change this in the configutor section of 2.1 but I couldn't change anything, is this correct??

One other thing that I noticed tonight is that when it misses the tps will drop say from a reading of 8 to say -1 the accel enrich will come on then so will the decel. At this point I ran a new larger power wire for test purposes directly to the battery and had the same problem.

any advice would be great.

Ron Foster · Post by **Ron Foster** » Sun Apr 02, 2006 4:21 pm

I have spent the last week reading and wiring

I have moved the MSD unit from under the dash and mounted it away from the ms2. I still have problems with the TPS dot and RPM. The car seams to have some minor missing and then will have large spikes.

also in an effort to eliminate the MSD as part of the problem I have taken it out and reset all of the dwell settings to just run the normal hei coil and still have a problem

I have created 2 data logs one with MSD and one without in hopes that someone could review and make recommendation

Ron Foster · Post by **Ron Foster** » Mon Apr 10, 2006 5:22 pm

Ok, I removed the MSD 6A and hooked back up to the HEI coil. This seams to make it run somewhat better but I still have a intermittant miss. I have added a ground wire to the MS2 case and added a larger ground wire from the motor to the frame. I have also made a steel cover for the TPS and grounded that. Still no luck. I then wired in a radio shack 12v filter. All this seams to have made only a small improvement
I have posted another data log of the latest run. You will see the rpm drop off as well as the timing .

Please reveiw and advise as I am running out of ideas

FoundSoul · Post by **FoundSoul** » Wed Apr 12, 2006 10:30 am

Looks like I do see one tach spike about 70% through that graph above--

Is this a 7pin HEI module custom fitted to the car or OEM fitted in the distributor? I'm wondering if there is anywhere that module could be picking up interference. If it's custom fitted did you use shielding for the tach wire?

THe other datalog of your current config might help-- the file above is the log viewer.

We may need to try and attract an HEI guru in here as well as my knowledge of MSing these systems in mostly book knowledge at this point as I can only have so many project cars... and right now I have 3 others going ;).

Try changing the thread title to take out the MSD reference since that's out of the picture now too, that may draw people that may not feel they can be as helpful if they don't know the MSD box, even if they know HEI well. If you do that update that first post so they'll know you started with MSD and then removed it, for the same reason...

krisr · Post by **krisr** » Sat Apr 15, 2006 1:13 am

Jerry, I don't think it's a dedicated HEI problem. I'm using the VR input / MSD Probillet distributor and getting something that looks very similar!... Another thing I noticed too is that the duty cycle drops off each time the spark does...

FoundSoul · Post by **FoundSoul** » Sat Apr 15, 2006 12:32 pm

I don't think it's an HEI specific issue either-- most likely some sort of EMI/RFI interference on the ignition input, either on the VR wires or on the signal wire from the HEI module to the MS.

krisr · Post by **krisr** » Sat Apr 15, 2006 10:02 pm

What about a bad solder joint somewhere in the VR circuit? You've done a couple cars using the VR circuit yeah? They didn't show any symptoms like these?

Ron Foster · Post by **Ron Foster** » Sun Apr 16, 2006 4:10 pm

thanks for the replys,

Yes this is a stock v-8 dissy with a 7pin module. I have taken the sheilded input wire out of the loom and ran it seperatly to eliminate any possible induction noise.I was also playing with the vr pot r52 and 56 and doesent seam to have any affect.

I will post another data log made today.

I have been playing around with the setting
predictor 30%
cranking 50%
afterstart 50%
normal 40%

As you will see I still experience the same spikes. At this point I would welcome any suggestions

krisr · Post by **krisr** » Sun Apr 16, 2006 6:00 pm

What spark plugs are you using? NGK's?

Ron Foster · Post by **Ron Foster** » Mon Apr 17, 2006 9:09 am

Thanks for the replys

Spark plugs are bosch.

Tofast are you thinking it could be a bad 7 pin module?

One other thing I seen in a simalir post is to upgrade to 2.35 software?

Thanks

lteeone · Post by **lteeone** » Mon Apr 17, 2006 9:50 am

i had the same noise when getting my VR input from a pro billet dist. I added some extra grounds no help.

I swtiched to a crank trigger and it cleaned it all up.

Ron Foster · Post by **Ron Foster** » Tue Apr 18, 2006 6:28 am

Well after loading the 2.35 code in to the ms2 I have had a little bit of luck, but one new problem.

Now I can get the tach spikes out at any rpm higher than idle. Once the car is in gear and the idle goes to say 750 a spike will occur and kill the engine.

I had to reset some of the ignition setings to

Predictor 10 to 18 % anything higher causes a mis
crank 50%
normal run 10 - 15% anythng higher causes a back fire
After start 40%

Would any of these setting contribute to a low rpm miss?

krisr · Post by **krisr** » Tue Apr 18, 2006 7:18 am

Ok after spending some time on mine today, I think I sorted out my tach drop problem. I'm sending the mag pickup straight to pin24 utilising the VR circuit. Dieselgeek (big thankyou by the way!) had advised me with a probillet distributor to adjust the hysteresis pot about 4-5 turns out OR to atleast smooth out low RPMs which I did, except I did mine at idle. I then adjusted zero crossing until my RPM picked up slightly, then backed it off 1 turn...

This MAY help you guys some of you guys using the VR circuit.

I'm using 2.35 code with these settings.
Algorithm: Last Interval
Gain: 20%
Cranking NPT: 66%
After NPT: 50%
Normal NPT: 22%

I took it for a drive later on tonight after declaring success and found it only stumbled ONCE! which to me is still a success as before I wouldn't even get 1km from my house and it would have ran out of fingers & toes counting the stumbles...

Ron Foster · Post by **Ron Foster** » Mon Apr 24, 2006 9:12 am

Success !!!!!!!!!!!!!

Changed the predictor algorithm to last interval and adjusted the vr pots some more.

Runs great in the garage, well see how it does tonight

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