Need Suggestions for Diagnosing a Ignition problem
Matt Maki
road. The car has been sitting for 2 years and had no problem starting
before it was retired. Effectively there is no spark at this time. To date
we have tried to clean all connectors, distributor and replaced the coil and
the high tension lead that goes from the coil to the distributor.
We have performed the normal tests as per Hayes repair manual. The test
that fail is where you disconnect the negative wire from the coil; remove
the high tension lead from the distributor; and with the ignition on, use a
jumper wire to momentarily connect the negative side of the coil to the
negative terminal on the battery whilst holding the coil high tension lead
close to the block. During this step, the manual says, that one should get
a good spark jumping from the HT lead to the block. Our result is a very,
very faint and short spark one time out of twenty. The ballast resistor is
not where it shows to be in the manual. Any suggestion as to how to proceed
from here would be appreciated (note: the car is not on the road at this
time, hence, we can't take it to the dealer).
Thanks!
Matt
Samuel D. Tyszler
Just a suggestion, you may have overlooked the battery. Try the test
with a known good battery rated with enough amps for your vehicle.
Batteries can go after sitting a while. Don't trust the voltmeters, it
can register 12 volts on a battery that is dead for all intents and
purposes. Maybe you have enough juice to get the starter going (If
your car cranks), but not enough to fire up the coil. You said that
you replaced the coil, so that is probably good now. Spark doesn't
seem to be making it into the distributor cap, so it is probably in
the circuit until the coil HT lead. If the battery is perfect, then
check the primary wiring for damage or disconnection, something might
be causing too much resistance. Depending on the type of ignition it
could be a module burned, but I don't think it is in your case.
none...@execpc.com
> I'm trying to assist my son in getting his 1981 Dodge Omni Miser 024 on the
> road. The car has been sitting for 2 years and had no problem starting
> before it was retired. Effectively there is no spark at this time. To date
> we have tried to clean all connectors, distributor and replaced the coil and
> the high tension lead that goes from the coil to the distributor.
>
> We have performed the normal tests as per Hayes repair manual. The test
> that fail is where you disconnect the negative wire from the coil; remove
> the high tension lead from the distributor; and with the ignition on, use a
> jumper wire to momentarily connect the negative side of the coil to the
> negative terminal on the battery whilst holding the coil high tension lead
> close to the block. During this step, the manual says, that one should get
> a good spark jumping from the HT lead to the block. Our result is a very,
> very faint and short spark one time out of twenty. The ballast resistor is
> not where it shows to be in the manual. Any suggestion as to how to proceed
> from here would be appreciated (note: the car is not on the road at this
> time, hence, we can't take it to the dealer).
>
> Thanks!
>
> Matt
Hi Matt,
Sorry to inform you that the tests in the Haynes manual are wrong.
You will never get an ignition coil to fire without some form of
capacitance on the negative side of the primary......bben there, done that
on almost every type of ignition coil on the market.
You can however make your own special test jumper from some parts to use
to test an ignition coil.
You will need to obtain a co-axial capacitor rated around .33mfd, a short
length of wire and three aligator clips....assemble as shown below.
I have found that the exact value of the capacitor is NOT critical.... .27
mfd will work (standard value for points ignition)
clip ______________| .33mfd |_____________clip
\ | capacitor |
\
\__________________________________clip
The finished piece will be a .33mfd capacitor with the jumper wire
soldered on at the left, in parallel with the capacitor.
Using the test cap is as follows....
Ignition key on...
Left clip...........connect to ground
Top right clip......connect to coil negative
Lower right clip....momentary ground to coil negative terminal
You should see a spark when momentarily connecting the lower right clip to
coil negative. If so the coil is OK.
As for the ballast resistor....there isn't one. The Hall Effect ignition
used in the Omni class vehicles didn't have a ballast resistor, as long as
you can measure battery voltage at the coil positive terminal you are
fine.
HTH
--
Neil Nelson
If you don't believe in something.....
You'll fall for anything....
Member of i-ATN....international Automotive Technicians Network
summer toys; 70 AAR 'Cuda #s match original not restored
see it at.... http://www.geocities.com/MotorCity/9426/photo_pages/orngcuda.html
64 Valiant 340 4bbl
winter toys; 95 Dakota SLT 4X4
88 Toyota Camry AWD
Matt
and was able to check the coil. It tested OK. Car is still not running but
we think we're closer to solving the problem. We now believe that the
problem is with the magnetic pickup / Hall Effect pickup assembly in the
distributor. Ordered a new part and hope to put it in tomorrow night.
Thanks again for your help.
Matt
none...@execpc.com wrote in message <6oacnj$6...@newsops.execpc.com>...
>In article <35a7e...@news.bc1.com>, "Matt Maki" <M.Hu...@BC1.com>
wrote:
>
none...@execpc.com
> Thank you for your assistance. Went to Radio Shack and purchased a capitor
> and was able to check the coil. It tested OK. Car is still not running but
> we think we're closer to solving the problem. We now believe that the
> problem is with the magnetic pickup / Hall Effect pickup assembly in the
> distributor. Ordered a new part and hope to put it in tomorrow night.
> Thanks again for your help.
>
>
> Matt
>
Glad it helped out Matt...
Here is a simple test for the Hall Effect Switch.
Disconnect the three way connector for the Hall Switch.
Hold the connector that goes to the ECU in your hand with the flat locator
up and the index tab down, should look like this.....
_________________
O 0
0
I I
Jumper the two top connectors, (paper clip will do fine) connect/
disconnect..etc.
Key on, check for spark while doing this. If you have spark then the Hall
Effect Switch is defective.
This test is called "poking its eyes out", because the connector looks
like a smiley face when positioned properly, jumpering the two terminals
simulates the same function to the ECU that the Hall Switch does.
The other hitch in the older 4 cylinder ignition systems is the ground tab
in the rotor. The shutter vanes on the rotor *HAVE* to be grounded. There
is a small metal tab on the rotor where it slides on the shaft that does
this, any amount of corrosion can cause a no spark in the system.