plaidside

I will post the rest of the patterns tomorrow.

There are two sides of an ignition system, the primary and secondary.
The primary consists of:
• Battery, ignition switch
• Ballast resistor
• Primary side of the coil
• Distributor points
• Condenser
The secondary consists off:
• Secondary side of the coil
• Coil wire
• Distributor cap
• Distributor rotor
• Ignition wires
• Spark plugs

This will be a condensed version of pattern interpretation.
These photos were taken by me on my scope. They may appear slightly different on your machine but all patterns are basically the same.
I did the best I could with the photos but some might be a little out of focus or fuzzy.


Here is a primary pattern in display mode. Look for uniformity of each cylinder and around 200 volts.
If the pattern is upside down then the coil polarity is reversed.


Here is a single primary pattern.
1 & 5 - points opens.
2 - Primary coil oscillations.
3 - Coil/condenser oscillations. If oscillations are missing or only 1 or 2 then it could indicate a bad coil or condenser.
4 - Points close. Look for sharp line. If not it could indicate worn or dirty contacts or point bounce. Also look for variation of the point closing; see next picture.
The distance between 4 & 5 is the dwell time.


These next two patterns are from an HEI equipped engine. You will need an adapter like this one in order to read the secondary patterns because there is no coil wire for the inductive clamp.


This is a superimposed pattern on an HEI distributor equipped car.
1- Point closings
2- Notice the variation in the point closings. This is the pattern you would use to check dwell.
It is hard to see but with HEI the dwell will be about 14 degrees at idle and as the RPM increases so does the dwell.
3- Also note the inverted V in the dwell section. This is a normal pattern for HEI.


This is a Raster pattern. Notice the point closings are not lined up.

Both of these patterns can indicate a bad distributor bushings, worn distributor cam or possible loose timing chain.

Any and all comments are welcomed.
Joe

GreaseMonkey

Damn - and my son was talking calculus to me tonight

Fast Jimmy

Thanks,
Fast Jimmy

Plasticman

Ditto!

John (Plasticman)

rgs

Good post.

If you can, you might also show a set for points systems. Similar but not exactly the same. Also, don't forget, for a points system, for every 1 degree change in dwell, timing is changed by 1 degree.

plaidside

If you notice this is part 1.
All my other pictures are for points. I used my Fuelie for the shots.
It will include sample problems and I will post them soon.
Joe

rgs

Sorry, I assumed (I know, I know) that the followup was going to be for the high voltage patterns.

jtranger

Joe, Would the patterns for a pertronix ignition be similar to the HEI patterns? I just purchased a scope and want to know how to read the scope with the pertronix. Great photo's and explaination! Waiting for part two!

Dads61

I'll jump in here and basically, yes, ignition is ignition, so they all are very close (even todays COP systems, etc look almost the same). Note he has 'points opening/closing' noted on the HEI pics, yet obviously there is no points. About the only really weird ones would be duel firing plugs(same cylinder) when they stagger the timing of the firing.
Always loved scopes, gives you a real picture of whats happening,either with combustion or a sensor. It amazes me to this day how the younger techs out there don't use them (and they are supposed to be the tech advanced generation). A lab scope is priceless to my eyes fro diagnosis.
Wait untill he gets to secondary, then you can see lean/rich issues, etc...very cool once you know it.
Cool thread Joe...

plaidside

I know I used 'points' instead of the transistor turning on and off. I am trying to keep it easy for people relate to.
My next series of patterns will be from a point car.
Joe

nassau66427

Thanks.

That is so cool; an EKG machine for the car.

I want a scope.

Dads61

Sorry, I should have been clearer, that was my point, that points on/off, transistor on/off is basically the same. Cool thread...

larrywalk

Very nice!

joewill

brings back memories working at the gas station back in my hippie days!
what was it called.. A sun machine?

http://cgi.ebay.com/ebaymotors/SUN-D...Q5fAccessories

plaidside

When I worked at Chevy in '72 this is the Sun machine I was trained on. That is one huge machine. It was state of the art back then.
It is way too big for the average garage.
Joe

rgs

That's the one I have and use in my personal shop. Easy to work on and repair if and when needed. I bought it from the community college I taught at 15 years ago.