Engine Keeps Losing Spark.... WHY ?

[Yinzer]

 My 85 Z24 has been losing spark. It normally happens after I shut the engine off and then try to restart it later.

 

 Now, it won't even fire up.

 

 I've replaced cap/rotor/both coils/wires/plugs/starter/battery and a new ICM.

 

 I reseated the ICM and put more dielectric grease under it and it fired right on up and ran great. Tried to start it the next day and NOTHING.

 

 I checked the gap from the Reluctor as well. All good.

 

 Sometimes when I try to crank it over, it sounds like the battery is straining to turn the starter. Yes, battery has been kept charged up. It will spin fast (normally most of the time) but at times will sound like the battery is straining. Completely random. Clearly something is a miss.

 

 What is going on with my truck ?

 

TIA

 

 Possibly bad Ignition Relay or Ignition Switch ?

 

 

[datzenmike]

How are you testing for lost spark????? Did you put a spark plug in one of the intake and exhaust side plug wires, hold against the grounded head and have someone to start it? Did you see spark or not???

 

Next time it's running check the timing hasn't moved or been set incorrectly. Should be 3⁰ BTDC.

 

 

 

I'm not a fan of swapping out coils for inferior after market ones unless I know for sure they are faulty. Also almost impossible that both would fail at the same time. The fact that it still does not start shows there was nothing wrong with the better original ones. Plugs/cap/rotor/wiring are high wear items and can be replaced.

[Crashtd420]

Clearly something is up...

How are you determining no spark?

 

Is it just because it wont start?

 

On the days it doesn't start is the temp warmer or colder out?

 

What do the plugs look like?

 

Next time it doesn't start, If you have a timing light, put it on the coil wire to the cap and see if its working... you should still see something even just cranking... 

 

Yes it can be done by pulling a wire and all that but what I'm saying keeps things in a working configuration...

 

The same could be done with a test light to the coil power wire and the distributor... this would tell you if something is not working when it should be...

 

 

[Yinzer]

8 hours ago, datzenmike said:

How are you testing for lost spark????? Did you put a spark plug in one of the intake and exhaust side plug wires, hold against the grounded head and have someone to start it? Did you see spark or not???

 

Next time it's running check the timing hasn't moved or been set incorrectly. Should be 3⁰ BTDC.

 

 

 

I'm not a fan of swapping out coils for inferior after market ones unless I know for sure they are faulty. Also almost impossible that both would fail at the same time. The fact that it still does not start shows there was nothing wrong with the better original ones. Plugs/cap/rotor/wiring are high wear items and can be replaced.

 

[Yinzer]

I set the Timing @ 5 degrees. That's what the label under the hood showed.

 

After I initially replaced the ICM, it ran very strong and smooth. Better than it ever has.

 

Next time I tried to start the engine, it refused to start.

 

 So, I reset the ICM and added a bit more Dielectic grease. The engine started right on up and ran great. Once I tried to restart it later...... NOTHING. Dead. Crank and crank and crank....... NO start.

 

 Possibly bad Ignition relay or Ignition Switch ?? How about the Reluctor ???

[Yinzer]

8 hours ago, Crashtd420 said:

Clearly something is up...

How are you determining no spark?

 

Is it just because it wont start?

 

On the days it doesn't start is the temp warmer or colder out?

 

What do the plugs look like?

 

Next time it doesn't start, If you have a timing light, put it on the coil wire to the cap and see if its working... you should still see something even just cranking... 

 

Yes it can be done by pulling a wire and all that but what I'm saying keeps things in a working configuration...

 

The same could be done with a test light to the coil power wire and the distributor... this would tell you if something is not working when it should be...

 

 

 

[datzenmike]

So the picture is what you used to test for spark???

 

Did you 'test the tester'? It works on a running engine?

 

 

[Yinzer]

58 minutes ago, datzenmike said:

So the picture is what you used to test for spark???

 

Did you 'test the tester'? It works on a running engine?

 

 

 Yes and Yes.

[datzenmike]

Alright. True intermittent spark.

 

Next time its not sparking get a $3 test lamp and test for power on the coil + terminals of both coils. 

 

If you have power but no spark...

1/ Does the power turn off while using the starter?

2/ Make sure the distributor is tightly bolted to the timing cover. It has to be grounded properly

 

If no power to both coils with the ignition on...

 

1/ Probably the ignition switch.

 

 

[DwayneOxford]

My '83 Subaru was giving me grief starting. Would start when warm but not cold. Jumped fire to + coil terminal, which solved prob.

Figgerd out the WELL worn switch was losing coil fire in crank mode. I pulled the harness connector for switch to be accessible, made a U of Romex to push in back side of harness connector, which insures fire to coil then remove after start up. Crude but effective. No one else can start it.

[Stinky]

Check your grounds.  Look for continuity to the battery from the dizzy, and to other spots too.

[stuart720]

Be sure to pop the distributor cap and give the wires going to the module at the base a good look over connections and all.

 

The vacuum advance system inside sometimes moves or even breaks the wires. Very poorly designed if you ask me. Had this happened to all 4 or 5 wires on my own. Spin the advance system by hand and where it stops is where the break happens. Had to lengthen an reroute 

Edited June 24, 2023 by stuart720
Mistake

[Yinzer]

On 6/13/2023 at 8:22 PM, datzenmike said:

Alright. True intermittent spark.

 

Next time its not sparking get a $3 test lamp and test for power on the coil + terminals of both coils. 

 

If you have power but no spark...

1/ Does the power turn off while using the starter?

2/ Make sure the distributor is tightly bolted to the timing cover. It has to be grounded properly

 

If no power to both coils with the ignition on...

 

1/ Probably the ignition switch.

 

 

 OK... Finally got a the chance to change out the Ignition Switch with a NEW one. NO CHANGE. NO SPARK.

 

 Power confirmed to BOTH coils and the ICM (inside the distributor). The Distributor is well grounded as well.

 

 Still NO spark. No what ??

 

 I did order a new ignition relay. One of the ones connected to the fusebox.

 

 ???

Edited July 18, 2023 by Yinzer

[Yinzer]

..........

 

Edited July 18, 2023 by Yinzer

[DwayneOxford]

Sounding like the distributor. The modules SELDOM go bad but can.

Have you checked fire straight out of coil wire?

Have you changed rotor button? Fire can go thru them to dist. shaft.

Have you checked side play in the distributor?

 

[Yinzer]

55 minutes ago, DwayneOxford said:

Sounding like the distributor. The modules SELDOM go bad but can.

Have you checked fire straight out of coil wire?

Have you changed rotor button? Fire can go thru them to dist. shaft.

Have you checked side play in the distributor?

 

Yes, Yes and not yet.

 

 I did notice some odd scraping on the side of the rotor. I'm wondering if there is a misalignment with the cap somehow. ??

 

 When I get the time, I'm going to swap in the old cap and rotor and see what happens. I'm still waiting on the new ignition relay. I have power to both coils so I guess the relay I have is good. Not sure. I'm throwing parts at it at this point.

[DwayneOxford]

If you got 12v to coil but no fire from coil wire it's coil, module or reluctor gap trouble from worn out top bushing.  

Edited July 19, 2023 by DwayneOxford

[Yinzer]

23 hours ago, DwayneOxford said:

If you got 12v to coil but no fire from coil wire it's coil, module or reluctor gap trouble from worn out top bushing.  

I actually did replace the distributor a few months back. The engine was having drivability issues since I bought it several months back. The original distributor had a broken vacuum advance nipple on it. I could not find a new vacuum advance so I bought a used distributor with one on it already.

 

The engine originally NOT restart and the first start of the day. Carb/Fuel issues addressed. Full tuneup parts, set timing idle all that. Decided to swap in a NEW ICM. Ran fantastic after I installed that. Best it ever ran. Smooth and strong. Shut if off. Next day came out to start and NOTTA ! Nothing... never started again after running perfect just the night before. I literally did NOTHING to it but come out the next day to try and start it.

 

 Now. NO SPARK.

 

 BTW, the new relay came in today. Replaced it and NO change.

 

 How could the ICM just go bad or reluctor gap change after running great the night before ?

 

 SO FRUSTRATED........

[DwayneOxford]

Prob not top bushing if new/reman dist. but all new means is it MIGHT work awhile. Electrical/electronic stuff does fail whenever. Might try ICM outta old dist. Only one coil fires until certain condition occurs. Might try jumping them together. 

[RyanC]

IS it possible the ICM is getting hot?  I had issues on my 510 years ago with l20b with electric ignition, my headers/extractors were very close and lots of issues it hot weather situations here in AU in stop start traffic.  ICM with new grease always made it better, we built a heat shield which stopped the issue.

[Yinzer]

8 hours ago, RyanC said:

IS it possible the ICM is getting hot?  I had issues on my 510 years ago with l20b with electric ignition, my headers/extractors were very close and lots of issues it hot weather situations here in AU in stop start traffic.  ICM with new grease always made it better, we built a heat shield which stopped the issue.

Not in this situation. I won't even run to get hot.

 

 

[Yinzer]

On 6/13/2023 at 8:22 PM, datzenmike said:

Alright. True intermittent spark.

 

If you have power but no spark...

1/ Does the power turn off while using the starter?

 

If no power to both coils with the ignition on...

 

Ok, While Cranking, Voltage drops to 10.5 Volts on the COIL Primaries.

 

NO Power to the C-TAB on the ICM.

 

There is 12 Volt Power to the ICM Tabs E, B, and I but NOT to the C Tab with Power ON and the NO POWER TO C TAB while Cranking.

 

I'm getting very, very close to throwing in the towel on this truck and Selling it AS-IS ! Seriously... I'm at my wit's end and have very few options to repair it otherwise.

 

 

[datzenmike]

Make sure battery terminals and clamps are scrapped clean and tight. 

 

Run a temporary jumper wire from battery positive to the positive terminal of the intake side coil. Have a care as this is not fused and it must not touch anything else. Try starting.

[DwayneOxford]

Have you load tested the battery? Could be dropping too low to work ignition while cranking.

[Yinzer]

3 hours ago, DwayneOxford said:

Have you load tested the battery? Could be dropping too low to work ignition while cranking.

It was new couple months ago. I do keep it charged up. Good idea to get it load tested. 

 

Would dropping voltage during cranking keep it from starting ? 

 

I am going to do the jump wire as Mike suggested when I get free time.  Hopefully tomorrow. 

 

 In the past when it wouldn't start, it WOULD BUMP start. You know, rolling down a grade and popping the clutch. It would fire right on up. Unfortunately, I can't do that now where it's currently sitting.