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Lost spark

bronconut73

Bronco Guru
Joined
Aug 7, 2012
Messages
9,916
Lost spark.


Grabbed a coil from the parts store on my way home the other day, as I thought my 22 year old MSD coil may have bit the dust.

But still no spark.

I have a tach driver hooked to my coil (2 wires on top)
I have the two distributor (Jegs Billet) wires on the bottom.
Then there is one original wire hooked to the side spade.
I assume it is from the ignition switch, but it's hooked to the - ground side of the coil.
That's how it was when I switched coils out so it worked before, but is that right?

Test light shows no signal coming from that original wire while cranking or just ignition on.
 

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Joe473

Sr. Member
Joined
Jul 16, 2012
Messages
950
Lost spark.


Grabbed a coil from the parts store on my way home the other day, as I thought my 22 year old MSD coil may have bit the dust.

But still no spark.

I have a tach driver hooked to my coil (2 wires on top)
I have the two distributor (Jegs Billet) wires on the bottom.
Then there is one original wire hooked to the side spade.
I assume it is from the ignition switch, but it's hooked to the - ground side of the coil.
That's how it was when I switched coils out so it worked before, but is that right?

Test light shows no signal coming from that original wire while cranking or just ignition on.
Disconnect your tach wires at coil first and make sure there is no short there causing issue. Run a temp jumper from battery to post side of coil and see if you get spark when cranking. If yes then it proves dizzy and coil is good and no you can start chasing wires

Sent from my SM-G900V using Tapatalk
 
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bronconut73

bronconut73

Bronco Guru
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Aug 7, 2012
Messages
9,916
The wire from the original harness (from the ignition switch) goes to the positive side of the coil?
 
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bronconut73

bronconut73

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Aug 7, 2012
Messages
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That worked Joe.

So I guess I need an ignition switch or that wire is toast.
 

Joe473

Sr. Member
Joined
Jul 16, 2012
Messages
950
That worked Joe.

So I guess I need an ignition switch or that wire is toast.
Is it a stock harness? Did removing tach wires get you spark or jumper from battery to coil?

If stock there should be two sources of hot feeds to coil. On the starter relay on fender when cranking there is a brown wire I think on I terminal. When cranking this gets + and goes inside dash and has factory splice just after resistor wire ends. On IG switch there is a feed from run position to resistor wire. When in run feed is from ignition switch through resistor wire to coil. When in start feed is from starter relay on fender routed inside cab meets end of resistor wire under dash and then to + side of coil.

If no power in either start or run check 3 wire plug at firewall and check wires from plug to coil.

Sent from my SM-G900V using Tapatalk
 
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bronconut73

bronconut73

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Joined
Aug 7, 2012
Messages
9,916
Coil worked for awhile straight wired with a little switch so I could test drive it.
But it has lost spark again.
Tried both coils.
They are getting hot.

Help?! Lol
 

B RON CO

Contributor
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Jun 29, 2016
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Loc.
Statesville, NC
Hi, one thing to address, unless you already have, is, you said the power goes to the -- negative side of the coil. That is wrong. Power from the switch, or a jumper lead goes to the + positive side of the coil. The negative side of the coil is for the distributor and tach. As mentioned, remove the tach wire for now. Good luck
 

Joe473

Sr. Member
Joined
Jul 16, 2012
Messages
950
Coil worked for awhile straight wired with a little switch so I could test drive it.
But it has lost spark again.
Tried both coils.
They are getting hot.

Help?! Lol
Can't run the coils like that for extended periods they are meant to have the resistor wire in the circuit except for when starting. You can burn up could that are meant for resistors like that. Just meant as a test.

Same for points and some ignition boxes. Can't leave power connected without resistor if meant for a resistor curcuit. You need to start going through that harness and find why you are not getting power to the coil in crank and run.

Sent from my SM-G900V using Tapatalk
 
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bronconut73

bronconut73

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Aug 7, 2012
Messages
9,916
I found that the post on the I post on the Solenoid is hot in crank and run so I ran a wire from it to the coil.

Is that okay?

Is the resistor wire the one with the rubber tag attached to it?
 

Joe473

Sr. Member
Joined
Jul 16, 2012
Messages
950
I found that the post on the I post on the Solenoid is hot in crank and run so I ran a wire from it to the coil.

Is that okay?

Is the resistor wire the one with the rubber tag attached to it?
Not sure if that would end up bypassing the resistor. Sure sound like your problem might be that 3 or 4 wire plug where the could wire comes through the firewall.

Sent from my SM-G900V using Tapatalk
 
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bronconut73

bronconut73

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Alright....
multiple symptoms/questions....


Ignition:

How do I recognize the "resistor wire" that should feed the coil?

Is it okay if the coil gets almost too hot to touch while engine idling for awhile (15-20 minutes).


Fuel system:

I installed my clear filter in my fuel line leading up to the carb, so I could see what's going on with fuel flow. Helps for trouble shooting. Yes I will remove it when I get this figured out.

Carter electric fuel pump.
Holley 670 T/A
Fuel pressure gauge under hood.

I see the filter is full.
I remove the float level plugs/screws from the bowls and fuel just barely dribbles out.
Pump the gas pedal a time or two and it should fire up....
But no....it appears to be starving for fuel....if I pump the hell out of the accelerator it will crank up and idle pretty good...but it takes a lot of pumping of the accelerator to get it to crank.

To clarify I have unhooked the choke in my effort to work on the carb, but this new symptom occurred before I unhooked it.
Also....I went ahead and replaced my primary float, accelerator pump diaphragm, and needle/seat just for shits and giggles....not sure why,...I guess just to take them off the list... lol.
But the float is dialed in perfectly.

So here I am with a full float bowl... but even though I pump the pedal a bunch it just barely cranks...like I can't get enough fuel into it.

A few questions from you guys pre-answered lol,

I am 100% sure I am not flooding it.

I do have spark now.

Once running it can be shut off and cranked instantly.

Once running great idle.

Plenty of fuel to the carb and in the bowl.

Drove it to Super Cel this year (Tennessee to Florida) with none of these issues.

During my efforts to correct this I have switched to an electric fuel pump. But everything else is the same. Electric fuel pump should be no issue as fuel flow to the pump is confirmed.

Help me brothers!
 

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Skiddy

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Joined
Oct 8, 2003
Messages
11,557
not too sure about the fuel issue, kind of sounds like it's loosing prime. on the coil it shouldn't be too hot that you can't keep your hand on it without catching fire;D
 
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bronconut73

bronconut73

Bronco Guru
Joined
Aug 7, 2012
Messages
9,916
not too sure about the fuel issue, kind of sounds like it's loosing prime. on the coil it shouldn't be too hot that you can't keep your hand on it without catching fire;D

It does seem like its losing prime but whenever I take the fuel line off the carb, the pump will shoot fuel out of the line pretty hard so no issue with filling the fuel bowl.

I agree about the coil.
Not sure how to recognize the resistor wire that is supposed to feed the coil. There is an original wire with a rubber tag on it??? But it is presently on my solenoid....
 
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DirtDonk

Contributor
Bronco Guru
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Nov 3, 2003
Messages
47,345
You asked for it...
Black Friday Night right back atcha!

How do I recognize the "resistor wire" that should feed the coil?

It's only the section under the dash, between the ignition switch and firewall. Depending on the year, it might be Red w/green coming out of the ignition switch, or it might be a faded pinkish brown.
It will also be wrapped in heat-resistant jacketing and most likely be strapped to the harness loom, but outside of the main taped branch to keep the heat away from the other wires and let this one breathe and stay cooler.

Is it okay if the coil gets almost too hot to touch while engine idling for awhile (15-20 minutes).

Yes. Or not...
Ignition coils get too hot to touch under normal circumstances. But that just makes it hard to tell when too hot is actually too hot.
Do you still have it jumpered to a full 12v? If so, then as was said you might be overheating the coil. Depends on the actual part number of the aftermarket coil as to whether it can handle 12v or needs more in the 6-9 range. The stock one needed the lowered voltage.
Got a part number?

I installed my clear filter in my fuel line leading up to the carb, so I could see what's going on with fuel flow. Helps for trouble shooting. Yes I will remove it when I get this figured out.

I know they have a bad rap/rep. But I've used them for years on many vehicles and never had an issue. I always kept a piece of split heater hose clipped around it between the hard parts and the filter to keep it from getting banged up. And never had an issue with the o-rings leaking either. Whether the plastic or the glass type filters.

Nothing wrong with taking it back off of course. Just that some of us have never experienced the trouble others have reported. So keep an eye on it at least.
Oh, and don't get troubled by the fact that it's not always full. I've seen filters with less than a quarter full of fuel showing and still feeding the engine just fine. I've also seen them as much as 90% full as well. But they do not have to be maintained at full to be fully flowing.

Pump the gas pedal a time or two and it should fire up... But no....it appears to be starving for fuel....if I pump the hell out of the accelerator it will crank up and idle pretty good...but it takes a lot of pumping of the accelerator to get it to crank.

When messing with the throttle can you see fuel shooting out of the squirters?
If not you have an accelerator pump problem. That would equate to a starting and acceleration issue. Not so much at idle, but everywhere else for sure.
The fact that fuel does seep out of the site plugs means that it "should be" high enough to fee the pump without issue.

To clarify I have unhooked the choke in my effort to work on the carb, but this new symptom occurred before I unhooked it.

While it will still work with it disconnected, it's likely contributing at least a little to the engine being hard to fire up when cold and stay running initially. There might be another issue because it was doing it before, but this is certainly a contributor now.

Also....I went ahead and replaced my primary float, accelerator pump diaphragm, and needle/seat just for shits and giggles....not sure why,...I guess just to take them off the list... lol.

A reasonable practice many years ago, but now can be very problematic. I've done it myself many times, just because I was in there already. But nowadays with the crap products, crap fuel, and crap that Broncos throw at us on a regular basis, changing parts before you know they need it can actually introduce new problems that make it much harder to diagnose the old issue.
So just keep that in mind if anything looks like a problem with the new part. Because it might actually be a problem with the new part!

So here I am with a full float bowl... but even though I pump the pedal a bunch it just barely cranks...like I can't get enough fuel into it.

Ok, so lets get this wording thing out of the way right now. I know generations of people use the word "crank" to mean firing up, but to me the word means, well, to crank. Which means the starter is spinning.
So if your engine won't crank, the starter is not working. If it cranks slowly, the starter or it's supporting cast are not working properly.
So if by "it barely cranks" you mean it's hard to get it to fire, ok. But if that in any way means that it's cranking slowly, like the battery is weak, then that's a separate issue.

Just wanted to make sure I knew what you meant when you said that. Guessing by all the previous comments that it's cranking just fine, but won't fire up and stay running easily. But had to make sure since "cranking" is what the starter does.

I am 100% sure I am not flooding it.

Good to know. But what about the squirters and their volume?

I do have spark now.

Is it on all cylinders and regular as checked with a timing light on each plug wire? And do you know it's properly timed still? Not sure if you even messed with timing or anything that could effect it, but even if not the distributor could have taken this moment to serendipitously decide to mess with you.

Once running it can be shut off and cranked instantly.

Multiple times and no trouble cranking? Fires up instantly and stays running?
Is it colder when it's giving you trouble? Then I would at least re-connect the choke mechanism and adjust it properly. You don't need it out of the equation as much as you need it for cold starting.

Once running great idle.

Driven it at this point yet? Does it accelerate normally? Or is it weak or boggy?

Plenty of fuel to the carb and in the bowl.

Could the dribble out of the plugs be residual from bouncing around? Or are you sure it's at that level and consistently dribbling out?

Drove it to Super Cel this year (Tennessee to Florida) with none of these issues.

This was before all this, correct? Did you touch the distributor at all?
During my efforts to correct this I have switched to an electric fuel pump. But everything else is the same. Electric fuel pump should be no issue as fuel flow to the pump is confirmed.

And finally, can you post up a close-up pic of the coil and it's connections?

Thanks!

Paul
 
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