Help!!
 

I hope you guys have an idea about this. When I let go of the trans brake button my car has begun to cut off & back on real quick. About a tenth off in 60' when it does it. Often only first pass of the day. I have tugged on wires, tightened grounds, replaced the trans brake solenoid, MSD box, crank trigger, disconnected the tach, etc. The battery voltage to the XFI ECU doesn't change when it does this. Two new NAPA batteries also. Only thing I wanted to replace last week was the microswitch on my Biondo button. Have a new on now. Going to test again Saturday. I would appreciate any ideas.
Thanks, Ed

Re: Help!!
 

Ed,
Have a look at this product from Shogun.

https://www.shogunindustries.com/cgi...ew_item=101003

It might be worth a call up there to see what their engineers have to say about your issue.

Chad

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Chad, a couple of years ago I asked about that and was told it was illegal for SS. I have wondered about a simple capacitor to try to dampen posdible voltage spikes. Pete Peery says he has a microswitch not open cleanly so it was bumping the 2 step again. I waited too long last week to find another microswitch and the problem was still there at the track Sunday. New one on it now, just looking for more things to look at before I take it back out Sat.

Thanks.

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I had an intermittant miss in my SS car. Drove me crazy,tried everything.Turns out it was the microswitch in the TB button. The vibrations would make it activate the 2 step. I replaced the switch and mounted the button on rubber to try to isolate vibrations.

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If it's only on the first pass of the day, perhaps it could be something related to the carb/jetting/vacuum signal. It may be momentarily too lean because the engine isn't "heat soaked" from previous runs and bogging.

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now you're gonna have Ed searching all over that LT one for a CARBURETOR. I know he's old but don't mess with him like that, lol.

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lol Oops. Well, he didn't say what he had and I didn't know.
But the theory is still the same - momentary lean. Don't know what may have changed from before the problem appeared. Just a possibility to consider.

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You have probably already checked this but pay close attention to anything going thru the firewall even if thick grommets are used. I have helped chase this stuff down on several cars that only happened on the leave and only for what seemed like milliseconds. Very small nicks not readily apparant to the naked eye. Seems that the offshore grommet sources quality control was lacking.

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Ken may have it. Pete Peery told me the same thing. I have a new microswitch on it now, maybe it's fixed. It's the only thing I didn't get changed out last week. Self employed, but you would think I could make a run across town to the electronics store to pick one up. This semi-retirement ain't very "semi" yet. Still busier than I would prefer. Got a new switch this week anyway. Two guys that had the same issue with the switch makes me feel a little more confident.

Thanks guys!

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The REAL solution to your problem is a Jerico transmission. That way you don't have to worry about a transbrake button going bad. LMAO!!!!!!!!!!!

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I like your style

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I always had stick cars before. They are way more fun to drive, no doubt about it.
I'm not up to more maintenance than I have now.

Now, GET OFF MY BUTT ABOUT BUILDING A STICK CAR!!
LMAO!

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Ed, does your XFI have an internal datalogger? If so can you view parameters such as rev limit signal voltage? My system indicates a certain voltage ....3.2 volts = rev limiter on 0 volts = rev limit off. May be a way of seeing if in fact it's being requested to be on. Also may have to set sample rate very high.... fast as comm will allow. Just a thought. Joe

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Joe, it does. I have never noticed that parameter. Sure something to look at!
Thanks Joe!!

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Big help there Chad. Big help. :-)

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I've spent all morning going over my car. I'm trying to get all those little things that never get fixed or looked at taken care of. Someone on here talked about a T-brake tripping at the wrong time. I got to looking at my switch and figured out I was having a similar problem. Last week my T-brake activated going up on the front end lift and going across the parking lot to load up and leave the alignment shop. You know, just a momentary thump/stumble type of apply. Well, best I can tell the little micro switch was set up in the button with partial travel already used up.
I could move the plunger less than .010 and the V/O meter would indicate a circuit. I think the odd /harsh vibrations of my little "V6" was shaking the switch enough to make a intermittent circuit. I took it all apart, moved the slope on the rod .040 and took the diameter of the rod where the switch roller rubs down to .340 depth. the switch lever starts to make contact @ .319. so I now have approx .045 travel in the plunger before the switch completes the circuit. (running SS I don't need the instant apply like a super class car) I also have the switch roller in a position where it is not touching anything when the switch is at rest. My thought there is no harmonics going through the switch lever. Well, I'll try to check it out next weekend. I think I'm going to find that thread and add my findings.
Ed, while I was reading this I thought of another issue that could be your problem.
If theses switches are all set up so close on the travel could the little spring in them cause a slight snap back when you release it? You know, like a valve bouncing on the seat. I always used a couple of shims on my switch and the spring seemed pretty soft so I tightened the spring up a couple of rounds. I figured I could take the shims out if it got too fast. Since it's been three years since I used a T-brake and I added a few B-days to myself I figure I've slowed down. :~) Good luck with it.

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Adger, you got me thinking more about this. I'm going tonpull that thing and measure that with a dial indicator, with my dvom connected. Thinking about my lab 'scope connected to see what kind of wave form I get with both the old and new switch to see if the new one is ant cleaner. It was too cold and wet to test today so we got some running around done. Think I can get in on a track rental Mon, so will do some investigation about this tomorrow (Sun).
Thanks for some new thinking about this.
Ed

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Ed, you have a PM

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always happy to help

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Just that kinda guy, right? LOL

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Just a big cuddly ray of sunshine.

Hope you get the problem fixed

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What I think I found is a failed spring inside my micro switch. I measured the travel on my new switches and found .043" travel for the roller on the lever would close the switch. My old one was so weak I had to hold the roller up to zero my dial indicator. It then only required .025" travel to close the switch. I think the new switch with more travel and a stronger spring will help prevent bumping the 2 step. The new switches (bought a spare) costs about three dollars at Affiliated Electronics. Cheapest thing on the whole car.
What you look for is called a short roller micro switch. Affiliated's part number for the switch is PH30-2080B. They are online.
Hope this helps somebody.

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Ed, what kind of button are you running?

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Joe, it's a Biondo Terminator. I've gotten over a half dozen private messages from guys having the same issue I had. Some just changed to a different style different button. Guess I'm either stupid or stuborn. Probably the latter. <G> I feel like this new switch will take care of it. Too cold to test here this weekend. Hope I found it.

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Well, it wasn't the micro switch on the Terminator button. Tested this afternoon at Tulsa. Still cuts off & back on. TPS graphs have been ugly, so changed it at the track. Also changed the FAST XFI ECU. Cleaned up the TPS graph. Still cuts off. Unplugged the rotory dial MSD 2-step selector, plugged on a rev limiter chip. No help. When it doesn't cut off the car is the fastest it has been. Can't race it like this.
If I find it I will post it with the hopes it might help somebody else.
Ed

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What are your wide band readings when it is cutting out?
Another trhing I've heard about are tachometer problems effecting the motor.

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Art, wide band doesn't change, voltage to the ECU doesn't show a change. Had the tach disconnected, still did it.

Thanks, Ed

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I couldn't get a good O2 reading below 5500 (the O2 sensor is in the collector). I had to put an extension and a muffler to get the O2 to read in the lower rpm ranges. I found I was lean leaving the line (it never showed on the dyno). The car would stutter, pop and bang, leaving the line. With the motor cold. Richening it up between 4500 and 6000 cleaned it up.

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I had this same problem and it turned out the Battery mount had broke at the bottom where I couldn't see it. Everything looked fine upon inspection but once the car launched it would rock out of the mount and short out on the chassis. I assume that since you changed your batteries that this isn't you problem but it sounds like some where down the line there is a short. May have to start tracing wires to see if any are chaffing and shorting out.

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Batteries aren't moving. Yesterday afternoon it cut off 5 out of 8 passes. Getting more frequent. It runs ten to twelve hundredths slower when it does it. Sounds like a loose connection, but according to the XFI internal data logger the voltage doesn't vary. May be too slow to catch it.

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Different battery? Maybe internal plates? I'm just guessing here

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Ed, Are you seeing any abrupt changes in your injector Pulse width or timing? If you can see it on the Datalogger lookat the Pulse width closely it should not change, if it does we;d need to see if it's due to some incorrect input. Wish I were more familiar with the FAST system, however diagnosis should follow the same approach. Please let me know if you see anything irregular as far as the PW or timing. Joe Forgot to ask what inputs are you using for Crk and Cam? Possible Crk sensor issue, as I believe Cam is only used at start up

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2 new 16 volt AGM batteries last week. Had 2 12s & alternator before that. No change.

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Joe, the pulse does narrow, but I'm not sure if it's the cause or effect from the RPM drop. Usually happens about 4900, drops to anywhere from 3900 to 3200, then right back up. Has an MSD crank trigger, no cam sensor. Replaced the crank trigger, MSD 7AL2Plus box, batteries, trans brake solenoid, micro switch on the Biondo Terminator, and the FAST XFI ECU, and TPS. I tugged on, wiggled, & flexed the wiring & battery cables. Only things I can think of are the ignition coil and battery cut-off. I have thumped on the cut-off and tugged on the cables, all while the engine was running. Couldn't make it miss. The TPS graph had gotten a bit eratic, new fixed that but had no effect on the running. I'm about ready to burn it. LOL

Today I replaced the ignition switch and wiring to the ECU and MSD box.

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Run a loop across the master cut off for one runuse BIG wire or just hook it to one pole. I had one of those give me fits on a S/C car.

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Adger, I put both cables on the same post yesterday. Probably won't get to test until Friday, unless somebody rents the track this week, and I can split the cost with them. Going tonput my old ignition coil back on it too. Running out of ideas.
Thanks.

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Ed you have a PM

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Got it! Thanks!!

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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.

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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.