I’m trying to diagnose why I still don’t have spark and I’m running out of places to look.

I replaced the…
whole Distributor with new unit
New Wires
Coil

Rechecked all my ground wires and scrapes ( 4 from the firewall, battery and ground strap on the frame. I’ve connected the coil wire with a spare spark plug I had to touch to the engine and still no spark.


I removed the smog pump and hoses, would there be anything on that section of harness that needs to be hooked up?

 

Year? engine?
Do you have a multi meter or a test light?

Your ignition key supplies power to the positive side of the coil your distributor supplies the ground. If the coil has power and a pulsating ground the coil should fire.

Check out spark testers. They have them at parts stores and Harbor freight. They are cheap. Worth owning if you have an older car.

 

It's a 1991 RS with the 305 Tbi… the motor was bad so bought another one and installed it.

I have a multi meter and a test light.

 

Do you have two profiles here or do we have two people with the same car and same problem?

 

Yes, I've been having issues with getting messages when I logged in through Facebook so I created a profile so I wouldn't miss messages.

Sorry for the confusion, just trying to be responsive when people offer advice.

 

The coil gets power from through the fire wall from the ignition switch and pulsating ground from the distributor. If it has both them and no spark the coil is bad. While the coil has both power and ground it "charges" and when it looses ground the field collapse and the spark discharges.

Connect your test light clamp to the negative side of the battery. Touch the positive side of the battery to make sure it works. Now with the key on in the run position no cranking check the positive side of the coil.

Result:
No Power: Report back here
Power: Try the same test while cranking and verify the power does not go away while cranking. Note power may flicker, that is normal.
If the Power is not there when cranking report back.

Now the distributer side.
Hook the Test light clamp to the positive side of the battery probe the negative side of the coil. This will be the side that comes from the distributor. You should get a pulsation light but only while cranking.

If you are not getting a pulsating flicker something is going on with the distributor. If you want you can go through testing the coil, Just search youtube for testing a coil. Keep in mind those test just tell us the coil can be good. You are testing for a short in the windings. There are other things in a coil that can fail that can cause a "leak" of power that will not show up in a bench test. The spark testers also have a built in resistance that stress tests the coil. If the coil will fire a tester it will fire a plug.

Another test you can do is just disconnect the ground side of the coil and jump a wire to the ground on the battery. Just bump the connector with the jumper wire. coil should fire each it.

The correct way to test that the pulse is right you need a dwell meter or a scope. dwell meter should read 90 degrees. It is pretty rare for a distributor to send out an incorrect pulse signal. Normally they either work or don't work.

 

Thank you for the great explanation.

As instructed, I checked my test light with the battery and it worked properly.

I then checked it on the coil, see picture. No power.

I did check the pink wire coming from the firewall and it has power

 

Additionally, this is a brand new coil

Carquest 26C1037

 

Well it is just 12 volts you can jump a wire from the positive side of the battery and see if it starts or at lease sparks. I can not see pics at work.

A big mistake many people make is assuming a new part is good. Even mechanics make this mistake. This is why I test everything. I even had one time a mechanic replaced every parts in a system. When I ran tests 2 different parts he replaced where bad. As a mechanic the worse thing you can see when you pop a hood is a bunch of new parts from someone trying to fix an issue. We call it a parts grenade. Some call it throwing parts at it. Now you are still dealing with the original problem and the possible problems of a new defective part, harness or connector damaged during the install or even a mislabeled part. Most trouble trees in the manual do not take into account 2 different issues in the same circuit. When I used to trouble shoot computer issues I had "known good" parts I kept at my box and that was GM OEM parts. GM's manufacturing standards are much higher then most aftermarket vendors (in most cases).

 

I tested the red wire coming from the firewall (grey plug) and it has power.

With the car on I checked the red wire from Coil (Black plug) going to the distributor and it has power when the engine is on.

It seems as though the power is coming through the fire wall and into the coil and out to the distributor correctly.

What are the white wires connected to from the firewall, is that the ground? If so, would it help to splice another ground wire to the white coming from the firewall to improve the ground?

Is there a fuse that is associated with the harness for the ignition?

Just grasping for places to look.

I painted the block and perhaps the ground studs on the back of the heads. Could that be creating a power ground?

Since its seems in the ignition somewhere, whats the place place to start to back track the wiring.

Are there any resistance settings I can check on wires?