Can a tach cause a problem with the ignition?
#692642
05/08/10 08:40 PM
05/08/10 08:40 PM
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Joined: Jul 2005
Posts: 1,303 Penna
70satelliteguy
OP
pro stock
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OP
pro stock
Joined: Jul 2005
Posts: 1,303
Penna
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Has anyone had a shift light tachometer cause ignition problems? I was told that something can go wrong internally and that it can cause a car to not even start among other problems! I have an Autometer shift light tach and a MSD digital 7 ignition and although the tach seems to work great I occasionally have a slight miss just as I shift from 2nd to 3rd.gear -occasionally on the 1-2 shift. That is the only time I have this miss.At no other time does it miss. Right at the shift point. It seems RPM dependent! I shift at 6500 and I have the upper rev limiter set at 8000. 2 step set at 4500 with no problems.Floats set 1/2 in window,fuel pressure at 7 psi, Magna flow 500 with return with 1/2 in. lines to front with 3/8 to carb. I have already replaced the MSD box,coil,distributor,wires,plugs, all relays,fuses and associated wires and grounds, Carb,fuel pump,filter,all fuel lines,fuel cell(no foam in fuelcell,)vents,intake and carb gaskets.Cleaned the fuel cell and fuel pressure regulator also. Just looking into if I should try and replace the tach also. Thanks Mike Thanks Mike
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Re: Can a tach cause a problem with the ignition?
[Re: 70satelliteguy]
#692647
05/08/10 09:54 PM
05/08/10 09:54 PM
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Joined: Aug 2009
Posts: 2,074 Mooresburg, Tn
'72CudaRacer
top fuel
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top fuel
Joined: Aug 2009
Posts: 2,074
Mooresburg, Tn
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Mike, I have a problem very similar to yours, but I've never thought about the tach being bad. Mine feels like its missing right at the top of the gear changes (5800 w/ RPM activated air shifter) and sometimes in the speed traps (depends on track). I finally figured out it was the rev limiter kicking in for just a split second. I can pull the high side chip out of two step and the "miss" goes away. I was thinking it was in the distributor, but it could be my tach? My tach is a Autometer monster tach with shift light, about 21 years old. I will change it this week... Brian
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Re: Can a tach cause a problem with the ignition?
[Re: Comp Chassis 2]
#692650
05/09/10 09:22 PM
05/09/10 09:22 PM
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Joined: Jul 2005
Posts: 1,303 Penna
70satelliteguy
OP
pro stock
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OP
pro stock
Joined: Jul 2005
Posts: 1,303
Penna
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"I can pull the high side chip out of two step and the "miss" goes away." 72cudaracer I have a msd digital 7 and I could try and pull the high side out of my 2 step to see if it goes away like yours did but if it does that would probably indicate that something was wrong with the msd box.I also have my 2 step at 4500 and the problem occurs closer to my shift point(6500 rpm) I have already replaced it (box)thinking it could be bad and unless I have 2 bad boxes that probably is not my problem? I am probably going to replace the tach to see if it fixes it! It will be relatively cheap compared to what I have already done so far! The fact that others have had similar problems leads me to believe this could be IT! Thanks Mike p.s. The only other thing I have not replaced is my linelock button on my shifter.It is pretty old and I suppose that when I shift it could be making slight contact and activating my burnout rev limiter for that fraction of a second.
Last edited by 70satelliteguy; 05/09/10 09:29 PM.
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Re: Can a tach cause a problem with the ignition?
[Re: Cab_Burge]
#692653
05/10/10 12:16 PM
05/10/10 12:16 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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I have also seen some of the MSD chips that were much less rpm that they were rated at... try a different chip EDIT Also poor grounds will cause issues
Last edited by MR_P_BODY; 05/10/10 12:18 PM.
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