Tony D Posted April 21, 2005 Share Posted April 21, 2005 I can spend a few minutes getting someone's MS-S unit running over the phone, meanwhile mine is acting up again. Can't even drive it now. BAH! Scratching my head on this one, started backfiring, and now has a "tach irregularity" again... Above 2500 it starts going haywire... So much for taking this one to MSA. Freezit didn't help. I will kill someone if I actually have a Bad CAS unit, that simply didn't show up until I drive the car to get it to 200F and good an heat soaked. I give up again. For another year. This sucks. Quote Link to comment Share on other sites More sharing options...
johnc Posted April 21, 2005 Share Posted April 21, 2005 This may not help at all, but... In my LT1 Corvette the PO had replaced the battery with a generic side and top post style. Well, the postive top post had a cheap plastic cover and it was rubbing on a frame bracket. Yesterday the car starting exhibiting the exact symptoms you describe below. Once I figured out the problem and replaced the battery with the correct one, problems went away. I wouldn't immediately blame Mr. Squirt. Check power and grounds first. Quote Link to comment Share on other sites More sharing options...
sims76 Posted April 21, 2005 Share Posted April 21, 2005 I have had the exact same problem in the past with no tach noise for a few days and then severe irregularity a few days later (especially when the engine is warmed up.) I have tried every pullup resistor, R10, and Dave Cap combination possilble. The problem was never compeletely fixed with my stock 76 VR Sensor in the distributor. I understand your frustration. I ended up buying a crank pulley with three magnets already mounted in it from someone over at zcar.com for $100. I then ordered samples of hall sensors from http://www.allegromicro.com for free. I now have no triggering problems at all. Nice clean signal. I'm not sure they have samples available anymore, and I have one more spare. If you need it let me know and I can drop it in the mail for you. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 22, 2005 Author Share Posted April 22, 2005 I am truly wondering if the 81CAS is marginal, and the signal deteriorates when heated. Sims, did you see your IN DASH tachometer start going crazy at the same time? I have not had the in-dash tach fluctuate UNTIL this last go-round, which leads me to think it's the triggering circuit in the CAS giving a bad sensor signal, and throwing everything else off. The in dash tach senses firing of the coil, so that pretty much isolates it outside the MS and what it's doing. All the MS does is pass through the signal it receives... I also note nobody with the 82/83 CAS is not having these sorts of problems... So when Moby says take it from a RUNNING DRIVING CAR, the only thing I have to add to it is LISTEN TO THAT ADVICE!!! I have another 81CAS that has been offered to me, as well as the stuff required to convert to the 82/83 CAS setup. It will have to wait till after MSA to diagnose further, I am hardheaded and want to PROVE beyond a shadow of a doubt that the 81 CAS is useable (which is pretty much a foregone conclusion) but after the modification to the pulley, I want to prove it again with full advance. Man, the way this thing pulls and the throttle response is phenomenal! And as an aside, I talked a guy through an MS problem the past two evenings (bought the stuff assembled) and his relay box had hard-soldered relays on the board! But we got it running the first night, and the next evening he DROVE it to Irwindale for the drags on Moby's maps! So I know the "back end" of the equation WORKS! It's just my "front end" that is making me appear as a "rear end"! LOL Quote Link to comment Share on other sites More sharing options...
sims76 Posted April 22, 2005 Share Posted April 22, 2005 Sims' date=' did you see your IN DASH tachometer start going crazy at the same time?[/quote'] Haha, yes I did. I'm using an MSD as my ignition module with an Autometer tach connected to the tach output of the MSD. The autometer reacts very fast and accurately so sometimes you could actually see exactly how high the spike was. You can actually SEE the tach needle vibrate when the tach signal is poor. As the car warmed up, the needle vibration would turn into jumping all over the place. Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted April 24, 2005 Share Posted April 24, 2005 was going to use 81 cas but i got a cherry hall sensor and magnets .so i have 2 81zxt cas units laying around. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 26, 2005 Author Share Posted April 26, 2005 Randy, I may have to stop through Modesto on the next trip up north! LOL Ianz has one from a good, running vehicle in his garage right now, and has offered it to me, so if that does it, then I may lay in a supply of "spares" because the 81 units seem few and far between. It also makes sense to "do the swap before you have problems", so anybody thinking of "rejuvinating" your 81 ZXT using MSS, realize GIGO! If the sensor is already bad, you will need to fix THAT before converting to MSS. The Magnet Trigger is sounding pretty good to me. My wiring is such that I could easily make a modification and run some triggers off either the cam snout, harmonic balancer, or the flywheel. That mod intrigues me, it lets me say "I built the trigger myself" also! Which would be neat in and of itself.... We are all truly diseased! LOL Quote Link to comment Share on other sites More sharing options...
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