Re: Help!!
 

Ed, I'll assume from the business you're in you have a DVOM? Hook it to the power supply circuit for your MSD or FAST unit, most have a record function to record high, low and average voltage set it to 1ms record speed and make a lap. If all looks well there, hook up to your crk. sensor circuit, also record set to AC voltage and monitor, a sudden change here would indicate an issue. Hoe are your Ign. components powered/ Relay, direct from switch? I have seen relays cut on and off due to points bounce, What sample rate does you datalogger have? Sorry for all the questions, just intrigued by the problem. Joe

Re: Help!!
 

Joe, I have a Fluke DVOM, and a Fluke 98A digital lab 'scope. Both will record, the 'scope has a faster capture rate than the meter. May have to make some passes with one of them connected. It's usually off close to 1/10th of a second. Don't know the sample rate for the FAST data logger. Need to check that.
I did replace those power wires to the FAST ECU and MSD box and the ignition switch Saturday. May have fixed it. Need to test again this week. I'm wearing it out chasing this down. Eight passes Friday, and accomplished nothing. I do know what it isn't. <G>
Thanks, Ed

Re: Help!!
 

Just thinking here Ed, have you tried a pass or two foot braking it? If it did the same thing then you could isolate from there, if not......How about all the non-tracked/under tracked stuff, injector harness perfect, fuel pump 100% ? I feel for you that is hell to try to figure out.


Good luck

Eric

Re: Help!!
 

.
"I did replace those power wires to the FAST ECU and MSD box and the ignition switch Saturday. May have fixed it. Need to test again this week. I'm wearing it out chasing this down. Eight passes Friday, and accomplished nothing. I do know what it isn't. <G>
Thanks, Ed"

Did you see anything with the wires?

Re: Help!!
 

Nope. I tried wiggling & tugging on the wires while it was running with no cut-off. I had those two wires running from a small fuse panel for "switched power" accessories. Now it's a double pole switch, one side powers that panel, the other side of the switch only powers the MSD box & FAST ECU directly. Had to make up new wires to do that. And that new switch. About to pull the rest of my hair out.

Re: Help!!
 

No Eric, I maybe should. I replaced the trans brake solenoid and microswitch. I think I'll record the waveform from the trans brake to see hig big of a voltage spike I may have.
Foot braking would isolate that circuit. Good idea.
Thanks, Ed

Re: Help!!
 

Ed,
Could the 3 step be faulty and sending a charge back to the T-brake?

Re: Help!!
 

Ed, is this thing a speed density set up, or does it have a MAF sensor?

What are you using for a distributor?

I want to go back over some of this, and see what you've replaced, or bypassed.

MSD box?
Coil?
Batteries?
Crank trigger pick up?
Coil wire?
ECU?
Transbrake switch?
Master switch
Ignition switch?
Transbrake solenoid?
Starter solenoid?
Battery cables?

Anything else?

Have you tried looking over all of the wiring, and using wire ties or "strain relief" to keep the wires from moving anywhere?

Have you tried tapping sharply on your electrical devices? I'm sure you're familiar with the old "tap test" that we all used to use checking things like the MAF years ago.

Also, what was changed, or what happened, immediately prior to this problem rearing its ugly little head?

Re: Help!!
 

Adger has a good thought, are you using a two or three step and if so at what RPM are the "pills"? Is one of them the same as the RPM engines dropping back to? Though I've never tried it I'd suspect even a small amount of voltage say 8-9 volts at the rev. limiter may be enough to activate it, where it would reqire full voltage to activate the trans brake. Joe

Re: Help!!
 

I use the 7AL2Plus boxes. Heard too many stories about the 7AL3 stuff. I use the rotory 2 step RPM selector, but did plug a regular chip in it's place Friday. thought I had it one pass, then it did it again. It is speed density. I have tapped on everything, flexed and tugged on wires. Only thing I have not yet tested, but it's next, is the master battery cut-off. I have banged on it, and jerked on the battery cables trying to make it cut off, mis-fire, something. Right now both battery cables are on the same post. Guess I'll find out this weekend. Wanted to rent the track, but they are working on it this week. Water problem near the finish line. Been so dry here, I can't imagine where it's coming from.

Re: Help!!
 

Any issues with fuel pressure? Though I'm sure you've looked it's not fluctuating is it? Joe

Re: Help!!
 

Very valid point about the fuel issues. At the Topeka National a couple years ago, my car would fall on its face after letting go of the tranny brake. Changed carbs, spacers, richened, leaned, etc and nothing worked. Then we looked at the fuel pump pressure from the pump to the regulator and it was way down from the original setting. Changed it and increased the fuel pressure from the regulator to the carb and it all went away. Turns out (according to Barry Grant) the regulator and pump were taking a nose dive. Ended up getting them repaired and sold all of them for Magnafuel. Best switch I have made so far.

Might be worth looking into. I believe we set the fuel pump to regulator at 28 pounds. Was at 15 when we were having problems.

Re: Help!!
 

Well, it may be fixed. Got 4 passes in last night without it cutting off. I'm crossing my fingers and going to Ennis next weekend. What I *think* it was, (changed more than one thing this week) is the battery ground cable. (This is an EFI car). It runs from the batteries to a starter bolt. This stupid flex plate shield required a twist in the cable to get the bolt through it. I soldered the lugs on each end. Looks like that pulled the solder loose. Not sure how it started as well as it did. But, fixing that cured it. Also added some redundant ground straps.
I want to thank all(several) the racers, many I have never met, for all the sugestions. You are a great group of guys!
Thanks again! Ed

Re: Help!!
 

Good news and good luck at Ennis.

Bill

Re: Help!!
 

Thanks Bill. Gonna need it. :-)

Re: Help!!
 

That's good news, glad you got it figured out. Not giving up is the key. Good luck Joe