2003 Grand Cherokee Coils

Lazarus · #1 10-11-2012, 11:43 AM

The 2003 Jeep Grand Cherokee (6 cyl) uses 3 coils on a coil rail (2 plugs per coil). The 4 channel #62152 will drive this setup, but will the stock coils take the high voltage from the MSD ignition? Does MSD make coils that will work on this vehicle?

Thanks!

msdtechsupport3 · #2 10-11-2012, 02:06 PM

This application will require a special tach adapter that is currently undergoing R&D. We are hoping to have this adapter available in the near future.
Without this adapter the engine generally will not run or will run with multiple mis-fires.

Lazarus · #3 10-12-2012, 07:55 AM

Thank you for the info on the tach adaptor. I would still like to know about the coils. Can the stock Jeep coils withstand the higher voltage output from the MSD 4-channel ignition, or do I have to fabricate a new coil setup with aftermarket coils?

I have a lot of experience with the tach adaptors. Until now they have been necessary to compensate for a low level trigger signal to the tachometer. In this case, the actual coil drive signal in the Jeep is used as the trigger signal for the MSD ignition. There is no separate ignition amplifier module. This Jeep ECU signal provides a hard ground to the coils. This same hard ground is the trigger signal required for the MSD. So the ignition itself should have plenty of trigger signal level. The tachometer drive in the Jeep is controlled by a separate line from the ECU. What does the new tach adaptor accomplish?

I haven't yet taken a scope to the Jeep ignition to confirm signal levels at various points, but I assumed that by 2003 the ECU would be using 12 volt pulses, instead of the 5 volts ignition module drive signal found in some older vehicles.

I suggest that you include information on the Jeep Grand Cherokee on the web site so someone does not go to a lot of work for nothing. Does the Grand Cherokee already have a multiple spark ignition? In that case it would not benefit from the MSD #62152 ignition.

I would like to discuss the Grand Cherokee details with the R&D dept, since I have also designed interface units for other vehicles. Perhaps I can be of assistance.

Regards,
Lazarus

msdtechsupport3 · #4 10-12-2012, 09:40 AM

Please keep in mind that the adapter is used to restore a "kickback" signal to the computer. The ECU uses this signal to recognize that the ignition system is functioning and can continue to fire the injectors. When the MSD ignition box is installed the "kickback" signal that is normally produced by the coils is absorbed by the box, the adapter has to restore that signal.
R&D is in the final stages and should be available soon (awaiting approval).

Lazarus · #5 10-19-2012, 08:27 AM

Quote:

Originally Posted by msdtechsupport3

Please keep in mind that the adapter is used to restore a "kickback" signal to the computer.

Agreed, that is probably what the Jeep ECU needs to see. Much of the MSD literature describes 'tach adapter' as a device that allows current driven tachs to be operated from voltage driven sources such as the MSD tach output. Maybe the Jeep device should be called an ignition adapter?

For this particular vehicle, an MSD ignition installation is looking more and more complex, unless a special harness is offered. We still don't know whether the stock coils can be used.

Thanks!

msdtechsupport3 · #6 10-19-2012, 11:05 AM

So far the prototypes in the field have indicated no problems with the stock coils being used with the MSD Ignition.

At this time we do not have an installation harness available for it.