Hey Jag folks. I was driving my 87 XJ6 SIII down the road and it suddenly died - engine turns, but will not fire even if bumped with started fluid. We have replaced the rotor button, coil and resistor, pickup in distributor, and HEI 4 pin module. We have confirmed that the cams are turning, rotor in distributor is turning. We have checked continuity of all electrical to and from distributor, coil, resistor and HEI module. We check continuity of distributor. We simply can't seem to get any fire on any cylinder. Any thoughts? Thank you!

 

Not 100% sure of your 12v supply to Coil, but if it is from ignition Switch to the Tach to + side of coil, you can jump 12v from + side of the battery to + side of coil and crank. If you get spark, then you have to TS ignition switch, Tach and wiring to + side of coil for an open.
Rgds
David

 

Looks like your Tach is connected to (-) terminal of ignition coil, so Ignition switch to (+) side of coil should be 12 volts with ignition switch in position 3. See attached wiring diagram.
Rgds
David

 

We are still having no luck, but we have confirmed that the coil is good. We believe that the problem is in the ignition control box shown in the picture. We replaced the module (twice), but are not quite sure of the two circled components. Anyone know what these are and/or how to diagnose their condition or replace them? Thanks!

 

I would definitely remove Capacitor for TS'ing as It can short out. Car will run fine with out it.

From memory when 350 Volt diode senses too much current that might damage module, it shorts to ground internally. If it is shorting to ground it could the be the problem.
Rgds
David


AB14 Amplifier Internals:

The Lucas 1.0uf capacitor is not available. (not required, is just for radio interference. May short out and cause ignition failure) Most all US cars with the 4 pin GM HEI Ignition system used a .3uf RFI (Radio Frequency interference) capacitor before 2000, later cars are using .47uf/250 volts capacitors for ignition coil RFI. You will have to modify mounting tab for installation inside amplifier, or you can just put the capacitor on Ignition coil mounting bolt. MOPAR 5149011AA Ignition Capacitor ($15), MOPAR 4606866AA, Standard RC26 or similar.

The Lucas 350-volt clamping Zener diode is not available. Although the (New Production) current 4 pin module shouldn’t need the extra external protection from a 350 Volt clamping diode. You can wire a 190-volt and a 160-volt clamping diode in series to achieve the desired 350-volt protection. (1N5387B, 190V, 5W ZENER DIODE) ($1.10) and a 1N5384B, 160V, 5W ZENER DIODE ($1.10) (E-Bay) Ground one end to one of the two mounting screws for the ignition module.

If you install a new module these are recommended.
Recommendations: Replace original 4 pin GM HEI module; with a Petronix D72000 ($75), a new ACDelco D1906 ($35) or a new Delphi DS10071 ($23) (GM 19180771). Stay away from “New Old Stock” and undocumented units from China, original specifications units were not reliable. “Meeting or exceeding” OEM 30-year-old spec. is not optimal). New specification production modules will allow you install a lower resistance coil (original 1.5-ohm coil down to a new 0.6 - 0.9-ohm ignition coil) and increase the spark plug gap by .005” over book.

o D72000: (California approved) Multiple sparks thru the entire RPM range.

o Adaptive dwell maintains peak energy throughout the entire RPM range, reducing misfires while improving engine performance.

o Peak current level is reached just prior to spark for maximum energy without the heat build-up, increasing coil performance and module reliability.

o Adjusts spark timing at higher RPMs to compensate for the inherent electronic delay.

o Senses startup and increases energy for quicker, easier starting.


o D1906: Feature electronically welded lead connections to reduce heat stress failure or cold joints

o laser trimmed to provide precise values and reduce deterioration and damage

o Increase voltage for the spark plugs to ignite the air/fuel mixture

o Include a copper slug heat sink to help dissipate heat and create a more stable environment

o Equipped with a large bus bar for added support and conductivity to address the installation and operating forces that stress terminal tabs


o DS10071: Original Equipment design and process ensures adequate heat transfer & durability

o Has short circuit, over-voltage and Electrostatic Discharge (ESD) protection

o Has internal current limit and precise voltage clamping circuits

 

Thank you David! We will give it a try and let you know how things turn out!

Alan

 

David, you are awesome. Taking these out of the circuit enabled it to fire. We will try to find replacements - apparently both of them shorted out. Hopefully not a sign of other problems, but this has been very helpful.

Thank you again.

Alan