repair aotomotive ignition control module?

[William R. Watt]

Has anyone repaired the ignition control module off a car?
I'm in the process of looking for someone locally who might take a look at
one. I 'll append a description below.

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Wondering if anyone would look at a small electronic device and
tell me if it can be diagnosed and repaired. The device is an
electronic ignition control module off a 1989 Ford Festiva. The
device sits inside the distributor and regulates when the spark
plugs fire. It gets a pulse from a pointer passing a magnet on the
rotating distributor shaft and opens a circuit to induce a small
current at high voltage to fire the spark plugs. From a discussion
in the rec.autos.tech newsgroup it seems its usually the
transistor used to open the circuit that fails on ignition control
modules. I've had to replace the one on my car twice since I
bought it in 1989.

I took one of the old ones apart. It's a small circuit board on a
metal base plate glued to a black plastic cover into which are
moulded the contacts for the wires on the distributor.

I've read up on early ignition control modules in automotive
electronics books from the public library. I made photo copies of
typical circuit diagrams. They may be irrelvant if all it needs is
to test the components on the circuit board and replace any bad
ones. According to the books there is a diode, some resistors, and
3-4 transistors in the basic circuit. There is also a wire from
the car computer to advance the timing under certain conditions.
That circuit might go through a signal converter which could be
the big square thing on the board.

It would be nice if this could be repaired. I understand
transitors don't cost much. I would like to post any information
on the Internet for other Festiva owners because they all have to
replace these modules. There is a website and a Yahoo group
devoted to Festivas.

There is an auto parts store on Merivale Road at Clyde which tests
ignition control modules for free. That's how I was able to trace
the problem with the car engine to the ignition control module. I
can also take a repaired module to the store for testing. I have
the printout from the earlier tests. It might help dignose the
failed module if needed.

 

[James Sweet]

Has anyone repaired the ignition control module off a car?
I'm in the process of looking for someone locally who might take a look at
one. I 'll append a description below.

If the module isn't potted in epoxy then repairing it shouldn't be too hard,
the transistor is likely house numbered though if it has any markings at
all, so some guesswork will be needed to find a suitable substitute.

 

[Jim Yanik]

If the module isn't potted in epoxy then repairing it shouldn't be too
hard, the transistor is likely house numbered though if it has any
markings at all, so some guesswork will be needed to find a suitable
substitute.

Transistors used in the flyback section of TVs would be a good choice for a
replacement.
But device packaging may be different.

 

[Dave Cole]

Has anyone repaired the ignition control module off a car?

I promise you it isnt worth it. My day job is as a diagnostic tech, and
I repair any circuits I can, but these are only useful for educational use.

I've had to replace the one on my car twice since I
bought it in 1989.

Twice in 14 years isn't too bad; these have to handle 300 volt or higher
pulses, high dV/dT spikes, high/low temperatures and thermal cycling, etc.

I took one of the old ones apart. It's a small circuit board on a
metal base plate glued to a black plastic cover into which are
moulded the contacts for the wires on the distributor.

These are usually thick-film hybrid assemblies on a ceramic substrate,
with active devices direct bonded and wire bonded (ie welded) connections,
and a silicone jell sealant/thermal equalizer over all. The power
transistor usually dies. Try buying just one bare chip power tranny, and
then try bonding and wire bonding it: I think youll prefer the small price
of a new one, instead. Some aftermarket units do use off-the-shelf
components, but still aren't worth the effort.

Good Luck
Dave Cole

 

[William R. Watt]

thank your for the information.
new modules cost $147 - $291 locally, transistors about $3.
the economcis look good and other owners report the same problems on the
Internet. I'd like to see if they can be reaired.

the wide range in prices at local auto parts sellers is interesting
because they are all selling exaclty the same module made by Mitsubishi
in Japan.

 

[R.Enns]

William,

I'd suggest going to the local auto wrecker, and buying up a half
dozen for spares. Surely they wouldn't charge you more than $10
apiece? The other option is to find another vehicle with similar
ignition system, and find an alternate that is more readily available.
GM HEI ignition parts are dirt cheap, but I believe they are designed
to work with inductive triggers.

Roger

 

[William R. Watt]

William,

I'd suggest going to the local auto wrecker, and buying up a half
dozen for spares. Surely they wouldn't charge you more than $10
apiece?

that would be great but I called all the wreckers in the yellow pages and
only found one with an '89 Ford Festiva. the module was used on the '88's
and '89s but they didn't start selling Festivas in Canada until '89. in
'90 they changed the ignigion system. I paid $75 + tax for the
distrubuteur off it and the module failed the test. (www.DIStester.com
sells testers to auto parts stores.)

.... The other option is to find another vehicle with similar

ignition system, and find an alternate that is more readily available.
GM HEI ignition parts are dirt cheap, but I believe they are designed
to work with inductive triggers.

good idea. have to think about how to do that.

I think some of the HEI systems used Hall Effect pickups and some used
magnets. the Festiva uses a magnetic (inductive?) pickup. I have some
diagrams of GM HEI circuits from an automotive electronics book at the
public library.

I just started looking through "Troubleshooting Analog Circuits" (1991) by
Robt. A Pease from the library today to see what's involved. The technical
stuff is all Greek to me but war stories are interesting.

 

[R.Enns]

that would be great but I called all the wreckers in the yellow pages and

only found one with an '89 Ford Festiva. the module was used on the '88's
and '89s but they didn't start selling Festivas in Canada until '89. in
'90 they changed the ignigion system. I paid $75 + tax for the
distrubuteur off it and the module failed the test. (www.DIStester.com
sells testers to auto parts stores.)

Wow, didn't realize they were that uncommon. There are some big u-pic
yards in the Toronto area that might be worth a look. Dominion in
Hamilton/Stoney Creek, and Standard in Markham come to mind.

I think some of the HEI systems used Hall Effect pickups and some used
magnets. the Festiva uses a magnetic (inductive?) pickup. I have some
diagrams of GM HEI circuits from an automotive electronics book at the
public library.

If you have a magnet rotating in your distributor, then I'd imagine
it's a triggering a hall effect transistor in your module. Inductive
pickups simply pass ferrous metal in front of a fixed magnetic field
created by the stationary sensor. In any case, there must be a way
you can modify your existing hardware to work.

Years ago I messed with distributor-based electronic ignition systems.
One that I found readily available, cheap and reliable was the
Mitsubishi system used in Hyundai Excel and Dodge Colts. The pickup
is a self-contained inductive pickup and coil drive system in a very
small module. Two wires to the coil, and you are done. I adapted
this system to another vehicle by simply swapping the entire system;
pickup, reluctor (rotating toothed wheel), and coil. You should be
able to adapt this or a similar system to your vehicle with little
difficulty.

Best of luck!
Roger

 

[William R. Watt]

.. Inductive
pickups simply pass ferrous metal in front of a fixed magnetic field
created by the stationary sensor. In any case, there must be a way
you can modify your existing hardware to work.

that's the one

Years ago I messed with distributor-based electronic ignition systems.
One that I found readily available, cheap and reliable was the
Mitsubishi system used in Hyundai Excel and Dodge Colts. The pickup
is a self-contained inductive pickup and coil drive system in a very
small module. Two wires to the coil, and you are done. I adapted
this system to another vehicle by simply swapping the entire system;
pickup, reluctor (rotating toothed wheel), and coil. You should be
able to adapt this or a similar system to your vehicle with little
difficulty.

a possibility. this module is shaped to fit the base plate inside the
distributor. it has one additional wire from the computer to advance the
spark when the engine warms up and the oxygen sensor starts functioning.

the ones with two more wires control the spark between cranking the engine
and when the O2 sensor warms up. One of them would work just ignoring the
two extra wires.

its good to have options to try.

 

[James Sweet]

that would be great but I called all the wreckers in the yellow pages and
only found one with an '89 Ford Festiva. the module was used on the '88's
and '89s but they didn't start selling Festivas in Canada until '89. in
'90 they changed the ignigion system. I paid $75 + tax for the
distrubuteur off it and the module failed the test. (www.DIStester.com
sells testers to auto parts stores.)

Perhaps you could get all the parts that changed off a '90 and swap over the
whole system? Or scrap the car and get something better, something that
should be possible for about what you'll spend keeping that thing going for
a few more years.

 

[William R. Watt]

Perhaps you could get all the parts that changed off a '90 and swap over the
whole system? Or scrap the car and get something better, something that
should be possible for about what you'll spend keeping that thing going for
a few more years.

the car only has 101k km on it and should run until its well over 200k. I
only put 2,500 km on it, summer driving only, no commuting. in very good
shape otherwise. the electronics they put in cars is making it difficult
for owners to do their own mainenance and repairs. every year they add on
more.

 

[[email protected]]

that's the one


a possibility. this module is shaped to fit the base plate inside the
distributor. it has one additional wire from the computer to advance the
spark when the engine warms up and the oxygen sensor starts functioning.

the ones with two more wires control the spark between cranking the engine
and when the O2 sensor warms up. One of them would work just ignoring the
two extra wires.

its good to have options to try.

Sounds like the spark curve is determined by the module, with the
engine computer having an input to induce a fixed iming change for
cold starts. In any case, this may present a problem trying to
substitute another module from a different vehicle.

You mentioned you opened the module up, are there any markings on the
transistor you suspect? If you have a multi-meter, do you read any
dead shorts across the legs (obviously blown transistor)?

Post a link to a picture if you can. I'm sure someone here can make a
suggestion for a possible replacement, but the trick is figuring out
what type of transistor it it (mosfet, scr, pnp, npn, etc). A
schematic of the circuit would be very helpful as well. For example
is one leg hooked to +12v or ground and which leg is connected to the
coil, etc.

I applaud your efforts to learn basic electronics repair. Having some
basic repair skills is allways handy and saves money in the long run.

-Chris

 

[James Sweet]

the car only has 101k km on it and should run until its well over 200k. I
only put 2,500 km on it, summer driving only, no commuting. in very good
shape otherwise. the electronics they put in cars is making it difficult
for owners to do their own mainenance and repairs. every year they add on
more.

That's not completely true, car electronics are generally quite reliable,
there's some dud designs out there though. I know I'd rather tinker with a
control module with a soldering iron than mess around with a carburetor.

 

[iliterate]

I am looking for modules to draw. They probably will die in the
reverse engineering process. If you want to donate one I will send you
a copy of the finished diagram. If interested I need:
Module,make and model of vehicle,permission to discard dead unit,YOUR
address.It may be a while before I get the schematic ready.
Roll-o
po box 1113 CASPER WYOMING 82601 USA.