Electronic Ignition Problems

[Bill Blue]

I've wired a GM HEI module into my car. The distributor is a stock 2.0 unit, converted for use with the Ford Duraspark module. I cannot get a spark. Suspecting a bad pickup unit, I tried shorting across the sensor pins of the HEI module as I had read the unit would operate with breaker points. No spark. Tried another coil. No spark. Bought another module, no spark, using either the distributor or shorting method. The module is grounded and wired properly. Any ideas?

Having hit a brick wall with the HEI, I tried a Ford Duraspark II module. It will spark only when the ignition key is turned on or off. Testing the pick up coil, I get 2.0 ohms. Checking another pick up coil I happened to have, get 2.0 ohms. Pick up coil lead to ground gives infinity. The distributor (including the electronic pickup) worked perfectly with a Duraspark module when last used 20 years ago. What's next?

Bill

 

[Ken Ellis]

Bill,

Is the engine block grounded?

In the case of the GM one, I tend to always suspect the 'conversion' wiring when interfacing modified equipment.

With the Ford, it's only triggering on the rising or falling edge of the power waveform... almost like it's expecting a distributor-like signal there, (rapid high-to-low transitions) instead of continuous system power.

According to http://zhome.com/ZCMnL/tech/gmhei.html#coil the characteristic of the signal from the distributor matters -- rising vs. falling. Look at point 18, starting with "By the way..."

Ken
As always, information, not advice.

 

[Bill Blue]

Hi Ken
Yes, the block is grounded. The car has a fully wired ground system. The heater fan and wiper motor are the only items not wired to ground. Was not aware the polarity of the sensing wires was important when using the HEI, so will reverse them. If that does not work, will check the reluctor/coil gap. That is going to be tons 'o fun.

The spark from the Duraspark unit when turning the key off is normal, leading me to suspect the problem is in the sensor. Especially as neither unit will function.

Bill

 

[RootesRacer]

Hi Ken
Yes, the block is grounded. The car has a fully wired ground system. The heater fan and wiper motor are the only items not wired to ground. Was not aware the polarity of the sensing wires was important when using the HEI, so will reverse them. If that does not work, will check the reluctor/coil gap. That is going to be tons 'o fun.

The spark from the Duraspark unit when turning the key off is normal, leading me to suspect the problem is in the sensor. Especially as neither unit will function.

Bill

Not likely a sensor problem.

Those sensors are dirt simple, if you read continuity but not a short, the sensor is good.
Its just a coil of wile wound around an armature.

Yes, polarity is super important. the way the sensor works is as the reluctor passes the stator sensor, it induces a voltage on the sensor output that rises then falls rapidly as the reluctor aligns with the stator. It is at this point that the ignition controller is supposed to fire. Get the polarity backwards and the output will rise instead of fall as the two align.

 

[Bill Blue]

Well, I've thrown in the electronic towel. Going to have to go back to points. Set the gap on the sensor wheel to 5 thou, changed sensor polarity several times, still nothing from the HEI and only shutdown spark on the Duraspark.

The only cause I can think of is that the aftermarket sensor is something that is compatible with neither the HEI or Duraspark, but what that could be is beyond me. I though they can the field pretty well covered. But I'm pretty sure I used a Duraspark with this sensor many years ago.

Maybe its just senility.
Bill