Are you ready for a real weird one? Random NO spark from a MP electronic ignition system despite numerous parts swapped around...

[Geoff 2]

Either the bat is faulty....or there is a current draw on it after the engine is switched off. I bought a 50 amp one wire mini alt [ with built in reg ] for my car. I noticed after installing the alt, battery would discharge after a few days. The alt had some sort of leakage to ground & new alt fixed the problem.

 

[Kern Dog]

Do it again but first create a draw, open the door so the dome light comes on...

The battery is in the trunk, the trunk has a light in it. I can still open the door and try your suggestion just to take it further.

It is certainly possible that there is a draw somewhere other than the trunk lamp.
I have a 75 Power Wagon that would lose charge to the battery and need a jump to start after sitting 2 weeks. I think that I traced it to an aftermarket Voltmeter that I had wired direct rather than to switched power.

 

[dodgeboy440]

While I state with guarded optimism that this issue is solved, I was wondering if low battery voltage could lead to ignition failures.
The battery in this car isn’t old but hasn’t held a charge like it should.
12.6 volts is what I’ve come to understand as a full charge. The alternator will get this battery there after a drive but when it sits, it drops off.
I drove it Friday evening and it tested 12.63 when I got home. It now reads 12.25. This may have been going on awhile. There are times it starts up quickly even after sitting and even then, I could have been well under 12.6 and not have known it. It is only the extended cranking that the starter gets slower that tipped me off that the battery voltage was low.
I’m curious if the alternator charging up the battery has any effect on the ignition system. Is it possible that the low running voltage somehow leads to ballast resistor of ECM failures?

Good observation….
It’s proven in the new multi computer controlled vehicles that battery strength is required for proper functioning! Look at the dual battery setups in the new vehicles with the “ stop / start “ feature that shuts off the vehicle when stationary. Gee thanks EPA !
A move by the OEM’s to improve CAFE to appease regulators…. Duh !

I don’t think IMO that our vintage Hot Rods
Are as sensitive to voltage reductions but maybe someone from MSD / Petronix / Halifax Shops could chime in……

I would surmise our simpler stuff doesn’t have the electronic load the newer stuff does but it still requires a base level of juice to energize for operation.

Mopar2ya!

Nice Ride ByTheWay!

 

[bm02tj]

I never read all posts but did you replace the pickup in dist as I have seen that to be intermittent and it is cheap thing to try

 

[MWbirdLOVER70]

The battery is in the trunk, the trunk has a light in it. I can still open the door and try your suggestion just to take it further.

It is certainly possible that there is a draw somewhere other than the trunk lamp.
I have a 75 Power Wagon that would lose charge to the battery and need a jump to start after sitting 2 weeks. I think that I traced it to an aftermarket Voltmeter that I had wired direct rather than to switched power.

Quartz unit in the clock if you have a clock? That was my draw so I disconnect my battery or leave on a tender. Also you mentioned a vaccum pump a while back for the brakes, is it hot all the time? Remember it’ll kick on when vac drops and could be your draw if battery hooked up. Just try to help brother

 

[Kern Dog]

The vacuum pump is wired to only run when the ignition is on.

 

[oldbee]

Glovebox light? Although u already said no draw with a test light in place of neg.cable. You just never know!

 

[kiwigtx]

You mean run a wire all the way back here?

View attachment 1633432

I have a ground on the ECM standoff bracket....

View attachment 1633433

It attaches to the rearmost intake bolt. I've even grounded it to other points on the firewall.
Aside from everything else, what I am wondering is....what can work fine then suddenly NOT work, then work again without touching it?
That seems like a riddle, I know. I mention it because that scenario has occurred.
I've always been able to get it started eventually. It has never failed me on a road trip. I do carry spare parts with me.

Did you do that wiring yourself Greg? ....or did you pay a Union Plumber to do it?

 

[oldbee]

Lol, all it takes is a regular test light probe, one end on disconnected cable and probe end on battery post.
All of you would be surprised with a little moisturized crud on top of battery leaking voltage down to ground. I’ve seen almost 1volt leaking down.

 

[Geoff 2]

^^^^^^^. Very true. The crap in the atmosphere settles on the battery & can certainly be conductive, especially with moisture & high humidity. This could drain the battery, but this would proably take days or weeks.

 

[Kern Dog]

Either the bat is faulty....or there is a current draw on it after the engine is switched off. I bought a 50 amp one wire mini alt The alt had some sort of leakage to ground & new alt fixed the problem.

The slow drain has been going on for awhile, before and after an alternator swap.

the pickup in dist

The distributor is new, the problem started before that swap too.

Quartz unit in the clock if you have a clock?

No clock. I appreciate the suggestions though.

Glovebox light?

No glove box light.

Lol, all it takes is a regular test light probe, one end on disconnected cable and probe end on battery post.
All of you would be surprised with a little moisturized crud on top of battery leaking voltage down to ground. I’ve seen almost 1volt leaking down.

Surprised? Well I was surprised tonight when I did just what you mentioned. Randy posted a video of it where a guy put a test light on the negative terminal and the other end to the cable. MINE lit up. Yeah...I was surprised since I had no idea that a negative terminal could power a light bulb. My electrical knowledge is really basic. I am almost embarrassed to admit how little I know of it.
For me, mechanical things are practical and real while electricity is invisible. I have a hard time grasping what I cannot see.
I tested the voltage last night and got a reading of 12.3? volts, I don't recall exactly. Tonight it was 12.36. The ground cables are disconnected. This showed that while voltage is below spec, it didn't drop off with the battery disconnected so I have more work to do.

 

[ckessel]

You could pop one fuse out at a time to id the problem circuit.

 

[Chargerkiddave]

I recall a similar problem long ago...with the test light trick if you start pulling fuses you'll find the culprit. I think...

 

[Chargerkiddave]

You beat me to it...^^^

 

[toolmanmike]

The slow drain has been going on for awhile, before and after an alternator swap.



The distributor is new, the problem started before that swap too.



No clock. I appreciate the suggestions though.





No glove box light.



Surprised? Well I was surprised tonight when I did just what you mentioned. Randy posted a video of it where a guy put a test light on the negative terminal and the other end to the cable. MINE lit up. Yeah...I was surprised since I had no idea that a negative terminal could power a light bulb. My electrical knowledge is really basic. I am almost embarrassed to admit how little I know of it.
For me, mechanical things are practical and real while electricity is invisible. I have a hard time grasping what I cannot see.
I tested the voltage last night and got a reading of 12.3? volts, I don't recall exactly. Tonight it was 12.36. The ground cables are disconnected. This showed that while voltage is below spec, it didn't drop off with the battery disconnected so I have more work to do.

You could pop one fuse out at a time to id the problem circuit.

I recall a similar problem long ago...with the test light trick if you start pulling fuses you'll find the culprit. I think...

Circuit isolation will help you diagnose the draw. (what circuit is causing the issue. If you pull the accessory fuse and the draw goes away, you know it's in that circuit.

 

[Kern Dog]

The process of elimination is often my most used tactic.
Thanks, gentlemen!

 

[1 Wild R/T]

So, reverse the method... Pull all the fuses & briefly install one at a time.... If with all the fuses pulled you still have a draw the draw is on an un-fused circuit, also there could be draws on more than one fused circuit so if you pull one fuse at a time but the light stays on because of the second draw you won't know that pulling the first fuse had any effect...

And yes, you want to temporarily install each fuse, don't quit when you find your first draw.....
It's probably the only one butttttt....