This is the 4 the run I made Sat. The 1st run looked normal on the engine rpm. Nice & smooth. Car went 4.66 @ 147. The 2nd run was fairly smooth but you could see some similar reading as this one in the start of the run. Car still went 4.66. The 3rd run was a little worse. Still went a 4.66. This run however was alot worse. Went 4.72 @144. I could hear it missing. Coil is a HVC 2. The big red coil. It is a 2015 model. The CT pickup is older than that. Pickup ohmed @ 81. Plugs were new AR3932. #7 & #8 almost looked fouled. I put an old set of NGK in & made a run. The front half of the run looked good but the back end kinda fell off again to a 4.68 @ 145.

Which ignition box and model# ?

MSD 7530T

The Data Acquisition that you are using lacks the ability to record the ignition pulses IN to the Ignition and what the Ignition OUT is doing. This DA information is / can be a troubleshooting advantage if available.

If you have the MSD 8276 CT pick-up 3/4"x16 UNF it should measure 70 – 90 ohms. You should also confirm this ohm measurement where the intermediate cable from CT pick-up plugs into the ignition box. This confirms that the cable is also good.

This recommendation has been written about before. If you are using a stand-alone Ignition ON toggle switch try replacing. If this is from a toggle switch panel try moving Ign ON to a different switch and output if possible.

Try removing any components attached to the RPM Output of the ignition box.

Try removing the alternator belt and run total loss ignition.

When doing Electrical component replacement, only do each 1 time and move on and not repeat.

What does the Battery Voltage show in the DA ?

Could possibly be mechanical. These problems can be tough to identify.

I measured the ohms on the pickup itself. I will measure with the extension cable that goes to the box. I am using the Digital Delay Mega Dial panel. So the ignition switch is on a panel board. Battery Voltage under load is 18.7

Because you have a DD Mega Panel that has an isolated Ignition ON output you can be assured that this is NOT the problem imho.

working off of memory ,i think a crank trigger did that to me once.i believe you said you could hear the miss

on that run i could her it for sure. The other runs it was so slight it did not affect the run but it showed on the log

quote:

Originally posted by rusty:
working off of memory ,i think a crank trigger did that to me once.i believe you said you could hear the miss

I had a 7AL-2 box go bad and it looked similar to that on the graph. I changed most every cap,rotor, plugs,crank trigger pick up, plug wires etc.

I have one of those MSD ignition testers thing that bothered me is MSD kept saying box tests good nothing wrong with it and kept trying to send me on a wild goose chase. Saying stupid stuff like the crank trigger wire may be too close to an ignition wire, the battery may be low, Blah, blah, blah but nothing is wrong with the box. Changed the box and problem resolved. Sent it in to TechWest and the box is good again.

With the 7530T I do not know if it can be repaired. I would check all of the easy low cost stuff and if it is not resolved try another ignition box.

Not sure about a MSD trigger pickup but the FIE and Leahy/Electromotion pickups I use are 40 ohms new. I know this because I had one fail out of the the blue on me last week

Well. I have been waiting on this box to go bad so I could switch to the Gris setup. Just wish I knew for sure. I guess i will have to TNT this week.

Did you check the screw that holds the rotor to the distributor? They loosen up if you don't use lock-tite or silicone,I check it frequently.

I will check it tonight. I replace that just last week. Didn't use lock tight. Be great if that's what it was.

So far my bets are hedging on the ignition switch, suggestion.

Not that it matters lol.

quote:

Originally posted by MorgretNation:
I will check it tonight. I replace that just last week. Didn't use lock tight. Be great if that's what it was.

Ok let rephrase that,the screw in the middle of the plate that the rotor bolts to. It's a small allen scew. Almost every race I will pop the cap off and give the rotor a twist to make sure it's not loose.

Yeah. I knew what you were talking about. I will check it tonight.

I had an MSD lockout plate on the distributor break and it had quite a bit of play but looking at it from the top looked good. Took me a while to find that issue.

After I found that I welded it up. Never going to use a mechanical advance anyway.

The answer to the question is yes, change the coil. Fought same issue, changing Grids and crank triggers, for it to be a new coil from that same time.

I hope to have some answers tomorrow.

Update. Made 3 passes today. I put a new set of AR3932 plugs in. Made a run Car is about 5-6 hundreths slow. Engine Rpm is all over the place like the log above. Came back put the new coil on. Same problem. Came back Changed the CT pickup. Same problem. Battery is 1 year old. XS 16v. Plug wires are 2 years old Taylor 10.4mm. MSD 7530T is from 2009. Cap & rotor are brand new this year.