p16 shows how the Duraspark ignition is wired.
BUT, on page 13 it says:
5. AFTERMARKET IGNITION SYSTEMS: If you are running an aftermarket ignition
system (MSD, Mallory, Jacobs, etc.), you might not have a coil signal that will
trigger our built-in tach filter. If your engine will not start, and you have one of
these systems, contact Howell Engine Developments at Ph 810-765-5100 for
So if you cannot get in touch with them, well, keep trying.
OR, on page 3 at the top:
THIS SYSTEM IS BASED ON THE PRODUCTION GM (Chevrolet or GMC)
THROTTLE BODY FUEL INJECTION AND ELECTRONICS, USED FROM 1986-91,ON
4.3 V-6 ENGINES. ALL BACKUP SYSTEMS AND “ON VEHICLE” DIAGNOSTICS
FUNCTION SIMILAR TO THOSE MODEL YEAR PACKAGES. THIS SYSTEM DOES
NOT CONTROL SPARK TIMING AS ON GM ENGINES BUT RELIES ON A TACH
SIGNAL FROM THE JEEP ELECTRONIC IGNITION FOR RPM INPUT TO THE ECM.
RPM input to pulse the injector.
Find the HEI tach output, and connect it to where the Duraspark setup connects to the harness of the TBI computer....
Negative side of the coil should suffice.