Problem with spark

[zimvsdib]

I could really use some help diagnosing and fixing a spark problem.

My car failed to start the other day so I put one of those "inline" spark testers to see if i had any visible spark.

(tip: if you are working alone, prop your phone up in the engine and record video of you spark tester or DMM while you go turn the key. Its also nice to keep your videos to have a record of your readouts)

There was 1 super weak micro spark and then nothing while i was cranking. I tried a couple times.
I thought it could be terminal connectors on the coil or ballast resistor so i made sure those were good.
Then i swapped out the coil and ballast resistor with a pair from other car that has no issues. Still no start.

I took some readings with a DMM. Here is what i got.(with the key turned on accessory position)
positive battery jump 11.68v
Left side resistor 11.12v
Right side resistor 11.12v
Coil positive 10.8v
Coil neg 1.91v
Coil center, ignition wire 10.82v (and when turning over my dmm goes from 7-9 volts)

Do these numbers seem okay? And what should i look at next?

Background on this car:
Car was working great this year.
Last time i drove it was about 2 months ago. But, I was testing a new fuel distributor (recently rebuilt, not from dmc.). It started fine but the idle was really rough due the the distributor so the cat went red and i went home.i didn't get a mile away. I haven't started it since.

I just installed a new fuel dist 2 days ago, newly rebuild from DMC. Injectors are cracked and ready to go, spray is good.
Alternator is only a few years old
1 year ago i did new spark plugs, dist cap, rotor and sp wires.

[Bitsyncmaster]

Left side resistor 11.12v
Right side resistor 11.12v
Coil positive 10.8v
Coil neg 1.91v

Resistor reading the same means no current in the coil but the voltage on coil says there is current. Does not make sense.

[David T]

Resistor reading the same means no current in the coil but the voltage on coil says there is current. Does not make sense.

The easiest way to test for spark is to shoot a little bit of Ether in and see if it does anything.

[zimvsdib]

Resistor reading the same means no current in the coil but the voltage on coil says there is current. Does not make sense.

Thanks for the reply!

You're right about that. I was using a different generic ballast resistor. Pictured below.
30892
This is the resistor setup that is currently in my operational time machine Delorean so i swapped on this car it in hopes of getting it to fire. ((back story on that: I had put a new john hervey 40k chrome coil in my car and had problems starting and running. The Mechanic said i had a weak spark because of that coil, he installed this black coil and replaced the resistor with this one. It has worked great since. I don't know what the specs on that resistor are but it's probably more High Energy Ignition style ))

I put the stock Bosch resistor back in and took new readings:
Left side terminal 9.30
right top terminal 11.14
right bottom terminal 7.47

308973089930900

Resistor measures .6 ohms on both right terminals.


David there is no spark so the Ether didn't work. no fire

[David T]

Thanks for the reply!

You're right about that. I was using a different generic ballast resistor. Pictured below.
30892
This is the resistor setup that is currently in my operational time machine Delorean so i swapped on this car it in hopes of getting it to fire. ((back story on that: I had put a new john hervey 40k chrome coil in my car and had problems starting and running. The Mechanic said i had a weak spark because of that coil, he installed this black coil and replaced the resistor with this one. It has worked great since. I don't know what the specs on that resistor are but it's probably more High Energy Ignition style ))

I put the stock Bosch resistor back in and took new readings:
Left side terminal 9.30
right top terminal 11.14
right bottom terminal 7.47

308973089930900

Resistor measures .6 ohms on both right terminals.


David there is no spark so the Ether didn't work. no fire

If you are running the generic coil, one of the most popular causes of no spark is a rusty, bad connection on the ballast resistor. The tabs are steel and rust. If you have a high performance coil. it is probably no good.

[zimvsdib]

If you are running the generic coil, one of the most popular causes of no spark is a rusty, bad connection on the ballast resistor. The tabs are steel and rust. If you have a high performance coil. it is probably no good.

I just tried both coils with a fresh battery charge and still no spark. I'll sand all those terminals to rule that out, but i have voltage at the coil as mentioned above.

I found another thread that seems very similar to my problem but unfortunately it goes quite
http://dmctalk.org/showthread.php?2145-No-Spark

[zimvsdib]

Is there a way i can test/prove that everything is working up to the ignition coil?
For instance if i try to turn the car over should i get a specific voltage from the HV coil wire that tells me everything is good up to that point?


I just wonder if I'm need to look further downstream, like the distributor pulse coil :(

I'd like to rule out everything else before i get a back ache from getting into the distributor.

[Bitsyncmaster]

When you turn the key to on, the ignition ECU is grounding the (-) side of the coil so you are driving current through the circuit. Your testing seems to prove that.

You are not testing the ignition pickup coil connection unless the engine is turning over. My guess is that is where your problem lies. That two pin connector on the pickup coil wiring was so corroded on my car I just cut it off and soldered the wires. That connector would be the first thing to check.

[David T]

When you turn the key to on, the ignition ECU is grounding the (-) side of the coil so you are driving current through the circuit. Your testing seems to prove that.

You are not testing the ignition pickup coil connection unless the engine is turning over. My guess is that is where your problem lies. That two pin connector on the pickup coil wiring was so corroded on my car I just cut it off and soldered the wires. That connector would be the first thing to check.

There is a very good trouble-shooting chart in the Technical Service Manual:
C1-Igniition System Diagnostic Chart starting on page 127

[Rich]

There is a very good trouble-shooting chart in the Technical Service Manual:
C1-Igniition System Diagnostic Chart starting on page 127

Good call. There are 5 sequential tests shown there in logical order.

C1-chart from pp126-127 is posted in a thread in the Resources section here in first 2 images: LINK: http://dmctalk.org/showthread.php?3142-Factory-Troubleshooting-Charts-Engine-Will-Not-Start (http://dmctalk.org/showthread.php?3142-Factory-Troubleshooting-Charts-Engine-Will-Not-Start)

[zimvsdib]

\You are not testing the ignition pickup coil connection unless the engine is turning over. My guess is that is where your problem lies. That two pin connector on the pickup coil wiring was so corroded on my car I just cut it off and soldered the wires. That connector would be the first thing to check.

Thanks, good idea. I'm going in today to cut off all the connectors and add new spade terminals throughout. I'll add the ignition pickup coil terminals to the list.

[zimvsdib]

thanks Dave, and Rich for the link!

[Bitsyncmaster]

Thanks, good idea. I'm going in today to cut off all the connectors and add new spade terminals throughout. I'll add the ignition pickup coil terminals to the list.

The pickup coil wire is a shielded wire. You may need a smaller connector for that small inner wire.

[zimvsdib]

The pickup coil wire is a shielded wire. You may need a smaller connector for that small inner wire.

This is what you are referring to correct?

I see, maybe i can find a smaller connector for that inner wire.

[Bitsyncmaster]

This is what you are referring to correct?

I see, maybe i can find a smaller connector for that inner wire.

Yes that is the one. There seems to be a lot of extra wire length so you have a lot of options for replacing the connector.

[zimvsdib]

Yes that is the one. There seems to be a lot of extra wire length so you have a lot of options for replacing the connector.

Ladies and gentlemen. This is a smart man.:bigclap:
Just like you said. I unconnected that plug and inspected it. The male side was fine but when I looked in the female end I could only see 1 side of the prongs.
Removing the rubber grommet revealed that the molex terminal had slid back and out of the connector.
As soon as I repositioned it, I was cruising around.

This is such an eye opener. I'm checking my components for problems and its the stupid connectors.
Both cars are getting all new connectors for the ignition system.

Open barrel f-crimp with a sleeved insulators. Maybe I'll even spring for those fancy weatherproof ones.

Again Thanks for everyone's help. This problem is solved.
Until next time...