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Big Mach
10-10-2003, 11:02 AM
Hi I use the 7al-2 with the pro power coil and i had the motor misfire randomly, tested at the track with one of your testers and it checked ok!
Next step was to replace wires cap rotor and pick up. No improvement!
The tach needle was bouncing around at the same time the misfire ocurred,so we disconnected the tach and the misfire disappeared. Do you know of other cases were the tach has been the cause of misfire?
The car is a NHRA stock -71 Mustang.
Thank you
Hans
:) :) :)

msdtech4
10-10-2003, 03:08 PM
Hans,

What kind of distributor are you using? The fact you can disconnect the tach and the misfire goes away tells us that it is a noise problem. What kind of plug wires are you running?

Thanks,

MSD tech4

Big Mach
10-10-2003, 04:10 PM
Msd billet distributor #8580 and heli-core spark plug wire #3119.
Other Msd products are noise filter# 8830,Three stage retard control#8970,Two step#8739,and rpm module selector#8670.
Tach is a Auto meter.
Thank you!
Hans

msdtech4
10-13-2003, 10:52 AM
Hans,

The wires that go from the MSD unit to the distributor, make sure these wires are not close to any other power wires, try to isolate these wires away from any other power wire or spark plug wires. If you have already tried isolating these wires, you may want to check spark plug wires for resistance, to much resistance on a wire may cause a lot of RFI noise (the Heli-core wires should be between 800-1200 ohms per foot). When checking the resistance, shake them around and see if there is any resistance change. If you have any electrical component like an electric fan or water pump try to shut these items down for testing purposes and see if it clears up.

Thanks,

MSD tech

Big Mach
10-13-2003, 12:06 PM
I found out that the mag pickup wires went through the same grommet as the power wires to the Msd. I will try to route them away from all other wires. Would it be wise to use the shielded mag cable PN 8862 ? The spark plug wires check ok for resistance.
Thank you for your help.
:) :) :)



Hans

msdtech4
10-13-2003, 12:24 PM
Hans,

That can defiantly cause that problem. The shielded cable is a good idea but you still need to isolate it. It is less sensitive but still needs to have some care take when you route the cable. Let me know how this works out.

Thanks,

MSD tech4

Big Mach
10-13-2003, 02:23 PM
MSD tech,
I will !

Thank you

Hans

msdtech4
10-13-2003, 03:07 PM
Not a problem!!