The Stovebolt Site Forums The Shop Area The Electrical Bay Weak if any spark and stumped as to why.

Went to fix a engine problem my nephew has with a Chevy inline six 230ci. Nothing fancy. standard one barrel, pretty much stock electrics. Would kinda start then die, then no start. Thought it was the carb but everything looked ok, then found very weak if any firing on the spark plugs. Went through the primary low voltage side of distributer i.e. points set correctly, good condenser, no shorting of wires, bypassed ballast resistor, good connections. Did the whole checklist and found nothing wrong. Thought that coil had gone south so we purchased a new one. Checked new and old with ohmmeter and both measured the same..primary about 2 ohms, secondary around 10k ohms (yeah, I know this is not the best test). Opened points with ignition on with screwdriver (old school side of the road test). Got spark whick would indicate a saturated coil I would think. Just no or very weak spark with either coil.
On the way home I was thinking of what I might have missed and the only thing I didn't do is check for current limiting. Remember, all the tests for voltage right to the hot side of the points were spot on as were grounds.
Anybody got any hint as to what I messed or better yet...what is wrong with this darn truck?

Try bypassing the ignition switch wiring with a jumper from battery voltage (battery + or the big charge lead of the alternator) to the coil + terminal and check for spark that way. You can get correct "voltage" but insufficient current flow through a dirty switch connection, loose wire, etc.

By far the most common cause of insufficient spark is a set of dirty or burned points. Remove them, and inspect them closely under a bright light. It's very likely you'll find something other than a clean, low resistance contact area. Try checking the voltage between the (-) coil terminal and a good ground with the ignition switch on and the points closed. If you get more than a couple of tenths of a volt indicated on the voltmeter, change the points.
Jerry

Get some copper plug wires and throw away the carbon ones you have.

I had the same problem and it was at the ballast resistor. My ballast resistor was double sided. Someone told me they think it is s Chrysler ballast resistor. I moved my wires from one side to the other side. I don't know if the resistor was bad or simply by moving the wires to the other side I corrected a bad connection.

Regardless, I would double check the connections and confirm you are getting the correct voltage through that connection.

Jerry laid out what I had planned to do next. Only difference being....it's got new set of points which were burnished by me with special points file which electronics guys carry in their tool bag for 'dressing' points used in voltage /current control systems. I am a retired electronic instrument and process control guy.
Copper wires with the original points/coil with radio delete is a good idea. I understand it stresses the ignition system as it draws more current than the original. But, this truck was running and the wires are fairly new. After I get it running I can suggest it to my nephew as an upgrade.
I installed the ballast resistor myself as the truck originally came with a resistance wire setup which has been chopped out by a PO. I jumpered out the resistor when testing with a fat alligator test lead.

Modern condensers are known for their poor quality! Just a thought.🛠

Copper wires are a giant leap backwards in technology. Install acetylene headlights and a hand crank while you're at it. RF resistance wires also prevent erosion of the contacts inside the distributor cap and the rotor. Low-resistance secondary wires create a mini arc welder situation inside the cap, as well as causing an extreme amount of radio frequency interference by the magnetic induction of current flow through the wires. A good RF suppressor wire will have less than 1,000 Ohms per inch of length, so a 12" wire is supposed to have less than 12,000 ohms of resistance. It will produce a yellowish spark, but that spark will still jump a gap of 1/4" or more with plenty of heat to ignite gasoline in a cylinder. A "fat blue spark" IS NOT YOUR FRIEND, no matter what uninformed people say.
Jerry

Beltfed, when you tested the 2 coils were you testing the coil wire to ground when it was being cranked? Did you duplicate the test with a solid core wire?
I second the Bat to coil jumper as the next test.
Bad distributor plate / body ground can cause the same problem.

I vote for the condenser also. They are cheap so its worth a try.

Well, a difference of options to say the least. I knew some of what Jerry stated when I said I know it stresses the ignition system. Unsure of "a fat blue spark is not your friend". I would think that a blue spark, being hotter, would be great IF it didn't cause all the problems Jerry related to. This is a 'grocery getter' truck that gets him back and forth to the coop with someone trying to buy it where ever he stops in his two horse home town. He loves that part.
I will have to 'cipher' on this, but only after getting this darn truck to run.

That information on resistance wires is straight from the General Motors Training Center instructors' seminars I attended from the mid 1960's to the late 1990's, so it's a bit more than a personal opinion. "Your mileage might vary".
Jerry

I don't quite understand Jims question. One coil test I did, and I did many, was ....made the primary side (+) hot, ran a solid copper secondary (high tension side) to grounded spark plug. Use an alligator lead from primary side (-) to battery negative just touching off and on it to simulate closing of the points. Got spark at battery as you should to indicate both continuity and saturation of coil (aka "kick back"). Said the hell with it and removed spark plug and replaced it with my trusty Simpson 260 thinking 'this ain't a smart thing to do. Repeated the test and got a movement of the needle. Well, now I know the coil is working but it ain't putting out enough high voltage.
So, as said before it got to be current limiting somewhere. My problem is, I don't live in the same two horse town (Danridge, TN) and it's over a 100 miles round trip.

Testing of parts, that are easy to change and cheap to buy, is a waste of time unless you are as experienced and knowledgeable as Jerry, have all the equipment, time and are able to accurately analyze it. Which no one is/does/can. The ignition system is as simple as it gets and is being made to seem like a nuclear reactor here. Ever heard of a tune up? Plugs, points, wires, condenser, rotor and cap.....and I guess a coil. Insure all proper grounds, If the timing is correct and you replace those parts and it does not have good spark, you probably live in the Bermuda Triangle. Can't fix that. Gotta move. Also, you absolutely can not trust what someone else has done or what they purchased or how they installed and calibrated it. Even if it's a relative.

Let's don't act like there is anything wrong with copper plug wires on an old truck. All other wires are copper conductor. Don't let Jerry confuse you with facts.
Suppressor wires, if new, should be fine. Copper wires will be fine. There are resistor spark plugs.

The ballast resistor has no polarity.

Be aware, although "kind of start and then die" is not descriptive, it does sound like a fuel problem. Also "Thought it was the carb but everything looked ok" What does that mean? Be sure not to get fixated on the electrical. If it fired, it has spark. There are a few things to check involving fuel supply but you did not mention what "looked ok" means exactly.
I will wait to see if you get good spark. Sometimes good spark it hard to test/see.

Now, with Jerry's ideas in mind. Do yourself and your nephew a favor. Buy another set of good points. Check, before you buy, that the contacts meet concentrically and faces contact on plane. Don't "burnish" them. Don't mess with them. Put them on and set them. We are going around in circles talking about electrical theory on an old truck. Testing a bunch of parameters and values like we are fixing a old IBM super computer. Meanwhile we are "burnishing" new points. Whatever that may mean to you. Anywhere from polishing to filing to sanding. Leave them alone if they are new.

I for one despise living in a 'throw away world'. Call me old school, cheap, out of touch, whatever. My garage and shop are full of stuff. Don't you dare call it junk like my wife does! It's just stuff I have not found a purpose for as of yet.
As to troubleshooting vs changing out parts. I see it as a sort of figuring out a 'who done it'. It also gives me a chance to use some of that junk, uhhh...I mean stuff.
With all kidding aside I will say this. With friends and myself driving hundreds of miles away from home in 50+ year old cars/trucks its nice for someone to have a very good understanding of how all the different systems work and how to troubleshoot them. This is because your just plain lucky if you breakdown in the parking lot of a FLAPS.

I throw nothing away. I don't like replacement as a method of fixing trucks. BUT there are many times I have wasted many hours trying to figure out what's wrong. The cost, the easy access to parts sometimes makes it a good way to quickly fix a daily driver that you all have, that you need daily. The new ignition parts are not a waste, just a tune up. You have done all this diagnostic/using your extra parts and it does not run yet. So I was cutting to the chase.

Also, I was still typing my previous post while you posted. If you want to re read, it may have extra info/opinion.

I value all options and suggesttion offered here. That's why I post here when I have a 'head scratcher'. Sometimes it's something I already checked and sometimes it's something I didn't even think of. It's like having another set of eyes looking at a problem. They will sometime see something you overlooked.
"Bartamos", I reread your post and your suggestions have merit. At times it's not worth beating a dead horse, just buy a new pony.
Thanks for all the inputs and I will post "the cure" when I get back to the truck for another crack at it.

Beating a dead horse can be beneficial- - - - - -it makes the steaks easier to chew!


Jerry

You say you have spark when you manually open the points. What happens when your assistant holds the spark plug against a good ground while you crank the engine over?

Every once in a while you see a very weak spark. I'd say about 10% of the times you should see a healthy spark.

Last time I had that, the timing was off one click. It sparked, but weak and tried to fire. Don't know if your Nephew took out the dizzy recently or messed with it's rotation. Better check timing ASAP. Check plug wire routing from No. 1. CW 153624. The spark at points does not tell you there is spark at plugs. Does not tell if it's timed. Does not tell if plug wires are clocked correctly.

It's beginning to sound like you're dealing with a bad condenser. "new" doesn't necessarily mean "good" and it takes a tester most people (not even me) don't happen to have handy. Try disconnecting the condenser temporarily and see if the coil, not the points, starts sparking. The condenser is there to protect the points, but it won't hurt to cycle them a few times without it connected, for testing purposes.
Jerry

Jerry, Bartamos, 52Carl, and others,
Be there,done that. Tested with and without condenser. No joy. Jumpered ballast resistor to get all the voltage possible to the coil. No joy. Did as Bartamos suggested and installed fresh set of points then put ran a business card through them to make sure no oil, finger prints were there. No joy. Pulled valve cover to check things topside and make sure timing mark, valve closure (rotated push rods with fingers), and rotor for #1 cylinder were correct. They were so again, no joy.
I'm losing sleep over this. So I'm making the drive back up to the lake house tomorrow to fix this truck.

Trucks were made to serve people and so it shall.

Not familiar with the term "no joy". What is the latest condition?....No spark? Still spark, but weak? Still spark at points? 12V traces all the way to coil pos? No cylinders firing at all? Some fire? No change with condenser disconnected?

New cap yet? new rotor yet? new wires yet? After sparking at points, that's all there is down the line. You would not think that all the wires would be bad, you would not think that all plugs would be bad. Some firing should occur and even start up with rough running should occur if all is timed, new ignition parts and plug wires right. You may have deep do-do valve problems, broken timing parts. Try moving the whole dizzy a bunch, both ways, to detect ANY change in behavior. Better or worse. Try changing point gap narrower than you think it should be and larger gap than you think it should be. Those babies can move as you tighten the screw.

Bad battery!, battery cables, posts...the starter will then take most of the voltage and starve the points/plugs to give weak spark. All looks good during static testing but weak while cranking.

Timing IS off!

Bad starter taking too much juice, try jumping

Bypass system screwed up

Ignition Partially grounded where it should not be

Dizzy case not grounding to motor/battery
Because Ground straps not viable from battery to motor, motor to sheet metal, sheet metal to chassis
Could be that simple

Just to confirm- - - - -you are sure the distributor is turning, right? A stripped timing gear can definitely cause a no start condition.
Jerry

Sorry for the military slang. It means an unsuccessful contact with an enemy aircraft. We used the term when we were fixing aircraft and we didn't fix the problem. It is turning. Tomorrow we will know so stay tuned.

Roger

I'm only 200-ish miles away- - - - -need some company on the flight line from an old autopilot technician?
Jerry

THE CURE !!! After a number of more hours of chasing our tail we found, but did not fix, the problem. I hooked up the (+) side of the battery directly to the ballast resistor, as suggested much earlier. That gave us a weak but consistent spark. Truck would start then spit, spudder, and die. I kept thinking....how in the heck do you get more voltage/current to the coil than a large gauge wire directly to the battery. Then, I guess by chance, I measured the run wire to the ballast resistor that was disconnected from the resistor with switch off. It measured 20 ohms to ground. So here we go again. Disconnected the connector on the fire wall and the 20 ohm to ground is inside the compartment. Again hooked to the ballast resistor directly to the battery but removed the run wire. The engine came to life and idled just fine. So, somewhere between the connector on the fire wall and the ignition switch and maybe the ignition switch there is a 20 ohm short of the run circuit wire. Ran out of daylight so it's left to fix another day.
You guys may see this sort of problem every day but for me, it goes in the "I don't want to do this again book". Who would think to disconnect the run circuit wire from the ballast resistor and measure its resistance to ground.

I spent several hours chasing a "master warning light" on a Mercedes coupe. This one was a big red rectangular warning light in the middle of the dash with a big exclamation point on the lens- - - - -impossible to ignore! The wire powering the light had a particular color code that went everywhere- - - -under the dash, into the engine compartment, under the vehicle. etc. After about 6 hours of unwrapping wire looms and chasing circuits I discovered I could turn the light off by jacking up the front of the car about six inches. More troubleshooting with no results. I finally found a wire with the same color code leading into the top of the brake master cylinder- - - - -to a float valve.

ADDING TWO OUNCES OF BRAKE FLUID TURNED THE LIGHT OFF!

The car owner was a doctor who owned the local hospital, a really good customer who kept me busy maintaining six cars his family owned- - - - -he got a freebie that night, and I learned an expensive lesson!
Jerry

Awesome job Beltfed. Your determination, intuition and logic is spot on. You got joy. Good work buddy. Now you are someone's favorite uncle.
Case closed.

Thanks for sharing the solution to your electrical issue. Sure you are glad to finally figure this one out and we all learned something.

Filthy German engineering.
Carl

It could be that there is resistance wire already in the harness. With the external resister you have too much voltage drop.

Wrenchbender Ret.
An interesting question as this truck came with that same resistance wire. I have the big shop manual for it and was high lighting the various wires that make this thing run on what Chevy calls a schematic. Anyway, the schematic calls out an "N" colored wire from the ignition switch to a connector, all inside the cab. Been at this fuse blowing game a very long time and have never seen a wire color labeled "N". The only thing I could come up with is, the "N" stands for Nichrome. Problem is I found no nichrome wire inside the cab. The only piece I found was on the engine side of the firewall, it has an inner sleeve and then wraped with a woven cloth, maybe fiberglass. I added the ballast resistor to make sure the voltage at the coil was correct.
When I'm able to return to the lake house where the truck is parked the shorted wire or ignition switch (could be either) will be repaired. I am going to rewire the whole start/run setup and put this mess behind me. I've got a garage at home full of neglected cars who need me.

Good point Wrenchbender. I failed to notice a 230 came out in 1962. Resistance wire was indeed used in that period on GM. I never asked the year. I also did not know that a ballast resistor was "added". Was assuming it was original to the truck. I have some 55-59 GMC schematics with N as Violet.

In this probable era, GM was switching to alternators/sensing wire/resistance wire/idiot lights........
Resistance wire was the new ballast resistor and has to be a certain length.

I completely blew it on this one.

"it has an inner sleeve and then wraped with a woven cloth, maybe fiberglass." That is resistance wire. If I knew what year vehicle I could study about it. Maybe you told? Don't see it. You don't want both, as WB said and as you found but didn't know what you found maybe.

I don't follow post 1221031, not even a little. I don't understand the symptom/diagnosis/analysis. I do follow you got it running.
Your idea to rewire that section is spot on. If you abandon the resistance wire, you can use a ballast resistor the old fashioned way.

Bartamos, I'll admit, that posting is somewhat 'wordie'. To 'boil' it down. When I attached a heavy jumper from (+) battery to (+) side of coil with alll circuits hooked up as normal, the truck would start then die. I then disconnected the run circuit wire from the (+) side of coil with jumper still hooked up. Truck started and continued to run. I then measured the resistance to ground of the run circuit wire with it disconnected at the ballast and ignition off. Resistance should be infinitedy as the wire is open at both ends. It measured 20 ohms.
In electrical jargon, I have a parallel circuit. One through the coil and points to ground. The other through a short in the wiring harness. This is not allowing the proper amount of current to travel through the coil thus causing a weak spark.
This would be the same situation as a leaking condenser or a pinched feed wire at the distributor for the points.
This is a 1964 C10 with a 230ci engine.
The wiring harness has been hacked on by a PO and we've all been through that mess. The normal resistance wire was shorten at some point so I was getting too much voltage at the (+) side of the coil thus the addition of the ballast resistor.
Sorry, still 'wordie'.

When I've encountered that nichrome wire on other applications, I've found that it was longer than necessary to reach from the firewall to the coil, and was doubled back inside the harness to provide sufficient wire length to get the proper voltage drop. The fiberglass and/or asbestos braid over the wire is spot on- - - - -same stuff I've found, apparently to avoid heat damage to the other wires in the harness.

A resistor only drops voltage while current is flowing, so if the points are open when a voltage test is made at the coil, the full battery voltage will be measured, all the way to the insulated point. As soon as the points close, then an accurate measurement of voltage drop across the various items in series in the circuit can be made.

Your diagnosis of an unintended parallel circuit with the coil is interesting, and very accurate, I believe!
Jerry