Exactly what is the function of the Duraspark ll ignition module?

Where does it fit into the scheme of things in the ignition system?

What could a weak one cause, symptom wise?

Just curious about this. I have read a lot of alleged functions of this little silver box. :-)

 

[updated:LAST EDITED ON 20-Nov-02 AT 10:19 AM (EST)] Ok, I may leave something out...someone correct me if I do.

The Duraspark II module pulses a ground to the negative side of the ignition coil every time the magnetic pickup in the distributor closes and tells it to... confused yet? Basically, the magnetic pickup takes the place of points used in earlier distributors and the circuit to the coil is completed and controlled by the D2 module.

As far as acting up, the Stock Ford modules seem most reliable, but when they do act up, they usually burn up or just die. The module is in the circuit to run the ign. coil, so if your magnetic pickup sticks closed, the coil will be energized all the time and burn up the module just like if you left the key on and burned up a set of points.

Welcome to the redundancy center for redundancy...Just kidding

 

As far as special functions, boxes with the blue grommet around the wires retard the timing on cranking, to allow for easier hot starts, while the ones with a brown grommet have special emmissions-related timing controls. I have heard different things about the ones with yellow grommets, but nothing specific. Aftermarket boxes aren't as reliable as factory ones, so you are better off getting one from a junkyard. Electric was pretty much right on with the basic function, except that the distributor pickup is actually a magnetic pulse generator. Every time a tooth on the distributor shaft passes the pickup coil, it induces a magnetic field. As the tooth moves away, the field collapses, iducing current flow in the coil. This small pulse is then sent to the box, which makes a decision as to whether or not it needs cranking or standard timing, then switches a transistor to control the coil.

Jared

 

Thanks for the replies on this issue.

 

 

Well, considering that these modules havent been used in years, are there aftermarket variations in these to correspond to the "blue grommet" and "brown grommet" etc versions?

 

Yes, there are aftremarket versions, but, it's better to go Junkyarding and get old ones, they're more reliable.
For a new one, the best one out there is the Ford Racing/MSD unit that has MSD guts, rev limiter and all that good stuff, but, it's like $200... It does plug directly into the factory harness though.
Evan

 

How do you test the module? I have an 84 F150 302 and has the blue grommet. I use a remote starter with a timing light on the coil wire. Sometimes I get no spark. Once in a while I do have spark and then it will start. It usually shuts off after a few minutes because it loses spark. The coil is new and don't appear to be the problem. Can Advanced Auto or Pep Boys test these?
Is there now a better aftermarket module out there today since the last post here was 2003?

 

A big problem with these units was their overheating due to lack of air-circulation under the piece. My '81 had the unit screwed to the inner fender well and I did have mysterious problems with the ignition in our Hot Texas summers. It actually got too hot to touch. Once the module cooled down, it was fine again. Solved the problem by mounting 1" spacers between it and the mounting surface.
Still works fine today! Telltale sign was the epoxy seal under the module showing signs of melting.

 

The parts stores can test these. But if it's a heat related problem, of course it will not fail in the store. It's best just to go ahead and buy another, and if it's not the problem, stick it under the seat and you will have a spare just in case.

 

Well I bought one today at Advanced Auto for $38. This truck is back from the dead. Now I have to work the rest of the bugs out. Thanks for the advice. I will see what happens when it gets hot outside.

 

I am glad your truck is back from the dead, but for some reason, those cheapo parts stores replacement modules typically do not last very long.

I don't know what Ford/Motorcraft kept to themselves when they made these modules, but the failure rate for the aftermarket replacements are very high. This is why the Duraspark ignition system gets a bad rap sometimes. I would go to the junkyard and find a MOTORCRAFT module and keep for a spare. You will probably need it.

Good luck!

 

I went through two from Autozone and they had a hard time starting right out of the box. They ran pretty well once they started. I still have the Motorcraft one, but it was throwing out a weak spark. I just installed an HEI module, and I can tell you it is a night and day difference.

 

Not to jack the thread, but would a Pertronix unit be a suitable replacement for this? Or would you not notice a difference? It would remove the need for the external box and is still electronic ignition. I use Pertronix ignitions in all my 60's vehicle and notice a huge improvement over the points and they have been completely trouble free even after 10 years of use.

 

It probably can not hurt, besides, if I am not mistaken, I thought it used a full 12 volts, allowing you to use a higher output coil (or at least giving you more from your existing coil).