Engine Keeps Losing Spark.... WHY ?

[Yinzer]

It does crank hard occasionally. Just like it's dropped voltage...but it's random. Next cranking will be fast..normal. Good like that a few times and then get a hard cranking again. Like I said, it's random. Why is it doing that ?

[datzenmike]

On 7/23/2023 at 2:40 PM, datzenmike said:

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]

Would dropping voltage during cranking keep it from starting ? 

 

I'm not sure but it might. What caused need to roll start? I'd sure try jumping it to see what happens.

Edited July 25, 2023 by DwayneOxford
forgot quote

[DwayneOxford]

7 hours ago, Yinzer said:

It does crank hard occasionally. Just like it's dropped voltage...but it's random. Next cranking will be fast..normal. Good like that a few times and then get a hard cranking again. Like I said, it's random. Why is it doing that ?

3 possibilities come to mind; battery not good, high starter amp draw, timing chain slop.

[Yinzer]

6 hours ago, datzenmike said:

 

Will do ASAP.

[Yinzer]

5 hours ago, DwayneOxford said:

Would dropping voltage during cranking keep it from starting ? 

 

I'm not sure but it might. What caused need to roll start? I'd sure try jumping it to see what happens.

It wouldn't restart after I had been driving it. Had couple folks push me, popped the clutch in 2nd gear and fired right on up.

[Yinzer]

4 hours ago, DwayneOxford said:

3 possibilities come to mind; battery not good, high starter amp draw, timing chain slop.

Has a new starter in it. New battery. I'm getting the battery load testes today sometime. 

[banzai510(hainz)]

Most batteries Load down during START

 

Thats why one th eolder Datsun with points ignition it bypasses the ballast resisitor.But its still not 12volts

 

clean connections.

 

Im doing a hail Mary here but maybe get a can of Quick freeze from a elelctrical store and spray the modul if you think something is getting HOT

[datzenmike]

2 hours ago, Yinzer said:

Has a new starter in it. New battery. I'm getting the battery load testes today sometime. 

 

Big mistake to assume that something that is new works perfectly. If you replaced the battery and no change then old battery was fine and the new one may have hidden problems that show up later. Same with starter, if it didn't fix anything then it was fine. Original equipment is far superior to $60 crap Chinese 'rebuilt' junk.

 

The battery can be eliminated by using jumper cables from another vehicle. If same not the battery. If better then could be battery or the charging system not good. That saved $200

 

Trouble shoot like a detective, find the problem and fix once.

[DwayneOxford]

6 hours ago, Yinzer said:

Has a new starter in it. New battery. I'm getting the battery load testes today sometime. 

Jump it, liked Mike said. When you get it started, go to a parts store that checks charging system

[Yinzer]

On 7/24/2023 at 5:20 PM, DwayneOxford said:

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

 The Battery tested all GOOD under load testing today.

 

I'm going to go do that Jumper wire thing in just a bit. Will report back the results.

[Yinzer]

7 hours ago, datzenmike said:

 

Big mistake to assume that something that is new works perfectly. If you replaced the battery and no change then old battery was fine and the new one may have hidden problems that show up later. Same with starter, if it didn't fix anything then it was fine. Original equipment is far superior to $60 crap Chinese 'rebuilt' junk.

 

The battery can be eliminated by using jumper cables from another vehicle. If same not the battery. If better then could be battery or the charging system not good. That saved $200

 

Trouble shoot like a detective, find the problem and fix once.

 The original battery shorted out against the hood when I was making a turn into a parking lot. That is when the electrical gremlin started.

 

 The starter was groaning and was worn out.

 

[datzenmike]

There should be a large gauge black ground wire to the body sheet metal near the battery. In some 720s the black negative battery cable to the intake is stripped to the copper and is bolted to the body next to the battery. The body MUST be grounded. The ground cable on the intake is for the high current starter but the engine/transmission/rear axle leaf springs and shocks are RUBBER mounted so electrical things on the body can't easily use the engine ground. The body needs it's own ground.  

[Yinzer]

7 minutes ago, datzenmike said:

There should be a large gauge black ground wire to the body sheet metal near the battery. In some 720s the black negative battery cable to the intake is stripped to the copper and is bolted to the body next to the battery. The body MUST be grounded. The ground cable on the intake is for the high current starter but the engine/transmission/rear axle leaf springs and shocks are RUBBER mounted so electrical things on the body can't easily use the engine ground. The body needs it's own ground.  

Yes. I've seen that ground on the corner of the battery tray. Looks like it could be better. 

 

Pics coming....

[datzenmike]

Check that the negative battery cable is clean and tight on the intake bolt. Might be faster to use a battery jumper cable from the negative side and clip the other end to the block or head.  If poor ground the distributor won't work so well.

[Yinzer]

Ok... Connected a jumper from + Battery to + of Intake Coil. I DID remove the wire from the + of the Coil. Not sure if I was supposed to keep it in place or not. DIdn't have time tonight to go both ways.

 

Anyways, when I had the jumper wire connected to the + Side of the Intake coil and touched the other end of the jumper wire to the + Battery Terminal, I heard a relay click under the battery. ???  I have no idea what that relay is for. Pic below.

 

When I had the jumper wire connected at both points and tried to start the engine, got NO SPARK. Verified with my Plug light checker. When the engine was OFF and key in the OFF position the Battery Light and Sensor light in the dash were FLICKERING. ??

 

 

[datzenmike]

Now we're getting somewhere.

 

Keep that jumper and add a ground to the distributor from the battery.

 

With power to the module and to the coil plus a known good ground there has to be a spark. If still nothing thenm could be the ignition module in the distributor. If the ground fixes the problem than the distributor is badly grounded.

[Yinzer]

1 minute ago, datzenmike said:

Now we're getting somewhere.

 

Keep that jumper and add a ground to the distributor from the battery.

 

With power to the module and to the coil plus a known good ground there has to be a spark. If still nothing thenm could be the ignition module in the distributor. If the ground fixes the problem than the distributor is badly grounded.

Gotcha. I'm going to redo the Ground from the - Battery to Body to Engine bracket (that's were the ground goes on this truck) or I could go to the Intake.

 

 Was I supposed to Disconnect the Wire going to the + Side of the Intake Coil or keep it in place ??

 

 I did buy another new ICM ($27). Should be here this Friday.

 

 Was that relay under the battery clicking ON have anything to do with all this ??

[datzenmike]

Engine bracket is fine as long as the block is well grounded. I replaced the battery cables on my 710 because I got a new side mount battery. The cables were from a Chevy Lumina. The ground cable was long enough to reach the starter bolt so I used that rather than cut it.

 

 

The clicking relay may be because the coil remained wired up. For now not a problem.

 

 

[DwayneOxford]

Outcome?

[Yinzer]

39 minutes ago, DwayneOxford said:

Outcome?

 Hopefully I'll know real soon.

 

 I haven't had to time to work on it and when I did it was 800 degrees here and a 1000% Humidity outside. Lol ! I live in Lower Alabama in the middle of a rain forest. The heat/humidity is brutal down here !

 

 I'll post up as soon as I know more.

 

 Q: When mounting the ICM, does the bottom require that white dielectric grease or not ? 

[datzenmike]

I don't think so. It's called heat sink grease, usually silicone. Won't hurt to try (Nissan didn't use it) but I don't think the module gets hot, it's more affected by outside heat, like the earlier matchbox mounted on the outside of the distributor. Radiator air is fine but some swaps place the matchbox module towards the nearby hot exhaust. Both the HEI on GMs and the Z series modules are totally enclosed in the cap or below the rotor. If heat was a problem for them we'd know by now.

[Yinzer]

1 hour ago, datzenmike said:

I don't think so. It's called heat sink grease, usually silicone. Won't hurt to try (Nissan didn't use it) but I don't think the module gets hot, it's more affected by outside heat, like the earlier matchbox mounted on the outside of the distributor. Radiator air is fine but some swaps place the matchbox module towards the nearby hot exhaust. Both the HEI on GMs and the Z series modules are totally enclosed in the cap or below the rotor. If heat was a problem for them we'd know by now.

I did use a fair amount when I installed it. I was more worried about the ICM not being able to get Ground due to the heat sink grease. Maybe over thinking it.

 

 Still have to reground the distributor. Damn heat/humidity here has been inhumane ! That and my damn tractor broke down. Been working getting that back up and running.

 

 Anyways... just out of curiosity. Can 4 plug wire distributor be modified to work in a Z24. Just leaving the Exhaust side plugs unused ??

[Yinzer]

Well, it's no longer 800 degrees and 1000% humidity.... but... it is 115 degrees REAL FEEL !! I'm a Damn Yankee ! Melting down here ! Lol 

[datzenmike]

26 minutes ago, Yinzer said:

I did use a fair amount when I installed it. I was more worried about the ICM not being able to get Ground due to the heat sink grease. Maybe over thinking it.

 

 Still have to reground the distributor. Damn heat/humidity here has been inhumane ! That and my damn tractor broke down. Been working getting that back up and running.

 

 Anyways... just out of curiosity. Can 4 plug wire distributor be modified to work in a Z24. Just leaving the Exhaust side plugs unused ??

 

The module is grounded through the two mounting screws.

 

You could run a 4 wire but 2 plugs per cylinder is there and it's more efficient. That's going backwards. A single plug will burn slower so the ignition will need to be advanced to 10-12 degrees BTDC to give it enough time to complete the burn and build it's maximum cylinder pressure at that sweet spot at about 15-17 degrees ATDC.