Help!!

[Ed Wright]

Got it! Thanks!!

[buzzinhalfdozen]

So the engine doesn't actually shut off it just loses power? You mentioned I think it sounds as if it's misfiring correct? I'd doubt you're losing voltage as I'd expect a severe "buck, backfire" as power were restored, I've seen this many times at work with intermitent power issues to various modules the veh. would act as though you cycled the ign.Did you mention you have a scope? If so this may help in diag. this issue, hopefully it has a "glitch" feature? The new crk. sensor is it the shielded type.... grounded to the block. I've seen many issues fixed mostly on the MSD digital units by installing the shielded type crk. sensor.

[Ed Wright]

Joe it sounds like the key was shut off and back on really quick. No backfire, pop, blubber, dropped cylinder, etc. Just cleanly off & on. The air/fuel shows 12.3-1 to 12.5-1 around there, which is where it has always had it's best 60' times. Has been cutting off about 4600 to 4900, and has always been back on before it drops to 3200. Hope to get to test again this week. Points race at Ennis next week. Need to find it. Also, if it blows the tires off it never does it.

No matter how embarrassing it might be, I'm going to post the results. Might help somebody else if it happens to them.

[buzzinhalfdozen]

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

[Ed Wright]

Originally Posted by buzzinhalfdozen

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

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

[Eric Merryfield]

Originally Posted by Ed Wright

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

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

[Ed Wright]

Originally Posted by Eric Merryfield

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.
I put a new ECU harness on it late last year. This started first race this year.

Good luck

Eric

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

[Joe Schweigert]

.
"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?

[Ed Wright]

Originally Posted by Joe Schweigert

.
"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?

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.