Plug wires arcing
Thread Starter
Navigator
Joined: Apr 2013
Posts: 9
Likes: 0
From: Westport Island Maine
Plug wires arcing
I have a 90 coup with basic L98 motor. After a re-build last year put new generic plug wires on. As we were sorting out various issues after the re-build, noted the wires were arcing badly. Replaced with AC Delcos for that motor, put in new iridium plugs. Still had arcing all over. Looked like fireworks at night in the engine compartment. I bought a set of double shielded 18.5 mm MSD wires, used two kits of plug wire harness things to get every wire separated everywhere. I'm still getting some arcing, though not as bad, and have a persistent SES light, Code 43 is the only code, which does seem consistent if I've got arcing. I still have the original coil, though the rest of the distributor is new. My question is: could a bad coil cause this? Something like low voltage- high amps (I don't know electrical other than there's some relationship between the two). When I installed the new wires I put a dab of dielectric on the connectors. The engine generally runs well, but little hesitation on acceleration, idles a little low, rough when cold, but well once its warm.
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
I'd go thru the dist and see that the module is plugged in well and be sure the ICM is beeded in a good glob of heat sink grease...
The arcing (to me) says extreme resistence in the circuit. The energy is having a hard time discharging as it should...thru the plug. Might want to add ground strap or cable to the head to frame or battery. If the block is not well grounded, that might create a resistence build-up. I KNOW cheap wires will do this..but sounds like you've gone wayyyy past cheapo stuff..
The arcing (to me) says extreme resistence in the circuit. The energy is having a hard time discharging as it should...thru the plug. Might want to add ground strap or cable to the head to frame or battery. If the block is not well grounded, that might create a resistence build-up. I KNOW cheap wires will do this..but sounds like you've gone wayyyy past cheapo stuff..
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
From another forum:
"Sounds like a loose or missing engine block ground wire. A quick check for this is to take a set of jumper cables, use only one side (black preferably.) Connect one end of the cable to the intake manifold on a good solid metal object and the other end to the negative battery terminal. This will provide a definite ground for the block."
"Sounds like a loose or missing engine block ground wire. A quick check for this is to take a set of jumper cables, use only one side (black preferably.) Connect one end of the cable to the intake manifold on a good solid metal object and the other end to the negative battery terminal. This will provide a definite ground for the block."
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
3rd on a good ground strap. Cant recall if the firewalls are metal or smc?
On older stuff wed always run one from the block to the frame one from the intake or bellhousing to the firewall min. One from chassis to body
Maybe your factory ones are merely loose or corroded??
On older stuff wed always run one from the block to the frame one from the intake or bellhousing to the firewall min. One from chassis to body
Maybe your factory ones are merely loose or corroded??
Thread Starter
Navigator
Joined: Apr 2013
Posts: 9
Likes: 0
From: Westport Island Maine
Grounding issues
Thanks for the responses, I'll check the grounding issues using the jumper cable test suggested above. When we pulled the engine winter before last for the rebuild, I took the opportunity to bright clean the grounding points on the frame rails, put new straps in when we re-installed the engine, with a thin coat of di-electric to inhibit corrosion, so I should still have good grounds.
Thread Starter
Navigator
Joined: Apr 2013
Posts: 9
Likes: 0
From: Westport Island Maine
Well I'm pretty confident that it's not ground issues. The ground strap from the left rear of the engine block to the neg post on the battery is new, nice clean bolt into the block, no corrosion. Put also a new ground strap from the bell housing to the the frame rail below the battery, nice clean connection, new screw in the fram, good bite, plus that's got a small wire also from that position to the neg terminal. I think I'm well grounded.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
You could be missing the ground on the coil or have a bad connection. Some have a wire, some have a metal strap. Somebody posted some pictures a while back showing this connection. Here ya go:
http://forums.corvetteforum.com/1581679328-post6.html
http://forums.corvetteforum.com/1581679328-post6.html
Thread Starter
Navigator
Joined: Apr 2013
Posts: 9
Likes: 0
From: Westport Island Maine
I'm still having the problem. The coil seems to be installed properly, ground strap and all. Some people have suggested the plugs themselves may be the problem. Currently I have some Denso Irridiums in there. Its been suggested that I should stay with AC Delco plugs. The standard AC plugs R45T specify for cast iron heads, and some don't specify. Is there a specific plug for aluminum heads? Also the manual says the gap should be .035, but AC Delco says the Rapidfire should be gapped at .045. I guess my main question is, can subtle variations in plug brands and designs really be responsible for for plug wires arcing all over the place, same for three sets of wires including the purported best high performance wires?
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I had arcing when I had a bad connection inside the plug wire. The spark couldn't get to the plug so it went to the nearest metal instead. Since you already replaced the plug wires this seems unlikely.
If the plug gap is too large you'll get the same effect. The spark can't jump the plug gap so it goes somewhere else.
The only other thing I can think of is that maybe the plugs are somehow insulated from the heads by a high resistance connection. Did you use some kind of anti seize or lubricant on the plug threads?
If the plug gap is too large you'll get the same effect. The spark can't jump the plug gap so it goes somewhere else.
The only other thing I can think of is that maybe the plugs are somehow insulated from the heads by a high resistance connection. Did you use some kind of anti seize or lubricant on the plug threads?
Thread Starter
Navigator
Joined: Apr 2013
Posts: 9
Likes: 0
From: Westport Island Maine
Thanks Cliff. I did put a very small dab of dielectric grease on both the threads and the plug wire caps. I'm going to clean that off and see if there's improvement. If that doesn't help I'll change the iridium plugs to some AC Delcos and confirm the gap. The iridiums came pre-gapped and directions not to mess with the gap.
Pro
Joined: Nov 2004
Posts: 641
Likes: 3
From: Long Island NY
I'm running NGK iridiums with Taylor Spiro Pro wires for years with no issues. I did gap mine. If you are careful not to disturb the center electrode, you can fine tune them. I would be surprised if the plugs were your problem (type).Check the gap though. Also make sure your wires are seated well at each end. By the way, I wouldn't use dielectric on the threads. I'd clean them off and use a little anti seize .
Last edited by artvette; May 23, 2013 at 11:53 PM.
Thread Starter
Navigator
Joined: Apr 2013
Posts: 9
Likes: 0
From: Westport Island Maine
Well I put in the AC-Delco plugs, gapped at .035, cleaned all the di-electric grease off the connections, still getting the same problem, Code 43, and from the sound, wires arcing (I didn't check at night yet) but it sounds the same. So I tried re-setting the code and starting the motor with a jumper cable from the block to the neg post on the battery, same result. I think I've pretty much eliminated grounding as the source of the problem.
I did notice while driving yesterday that the volt meter on the dash looked like it was reading high, maybe 16-17, its hard to tell with the analog meter and and a small scale. I also noticed that the needle jumped around occasionally when there was no change in engine speed. So I'm wondering if I have a bad voltage regulator or alternator, and, if high or erratic voltage into the coil would effect the coil output such that I would get that arcing? Anyone have any experience or insight on that angle?
I did notice while driving yesterday that the volt meter on the dash looked like it was reading high, maybe 16-17, its hard to tell with the analog meter and and a small scale. I also noticed that the needle jumped around occasionally when there was no change in engine speed. So I'm wondering if I have a bad voltage regulator or alternator, and, if high or erratic voltage into the coil would effect the coil output such that I would get that arcing? Anyone have any experience or insight on that angle?
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
Your problem is in the secondary (high voltage) side of the ignition system. That eliminates any block-to-battery ground issues. The circuit includes the ignition coil, rotor, cap, plug wires, plugs and the engine block.
The voltage starts at the coil, goes through the button in the cap to the rotor, jumps to the terminals in the cap, goes through the plug wires to the plugs, jumps the gap in the plugs and then returns through the engine block to the metal distributor body and from there goes through a ground connection to the coil. Somewhere in that series chain of connections is a high resistance that isn't letting the voltage get to where it's supposed to go.
Did you check the black wire that comes out of the coil and goes under one of the screws that holds the coil? That's the ground wire for the coil secondary. It's shown in the picture in the link I posted previously:
http://forums.corvetteforum.com/1581679328-post6.html
The voltage starts at the coil, goes through the button in the cap to the rotor, jumps to the terminals in the cap, goes through the plug wires to the plugs, jumps the gap in the plugs and then returns through the engine block to the metal distributor body and from there goes through a ground connection to the coil. Somewhere in that series chain of connections is a high resistance that isn't letting the voltage get to where it's supposed to go.
Did you check the black wire that comes out of the coil and goes under one of the screws that holds the coil? That's the ground wire for the coil secondary. It's shown in the picture in the link I posted previously:
http://forums.corvetteforum.com/1581679328-post6.html
Thread Starter
Navigator
Joined: Apr 2013
Posts: 9
Likes: 0
From: Westport Island Maine
Your problem is in the secondary (high voltage) side of the ignition system. That eliminates any block-to-battery ground issues. The circuit includes the ignition coil, rotor, cap, plug wires, plugs and the engine block.
The voltage starts at the coil, goes through the button in the cap to the rotor, jumps to the terminals in the cap, goes through the plug wires to the plugs, jumps the gap in the plugs and then returns through the engine block to the metal distributor body and from there goes through a ground connection to the coil. Somewhere in that series chain of connections is a high resistance that isn't letting the voltage get to where it's supposed to go.
Did you check the black wire that comes out of the coil and goes under one of the screws that holds the coil? That's the ground wire for the coil secondary. It's shown in the picture in the link I posted previously:
http://forums.corvetteforum.com/1581679328-post6.html
The voltage starts at the coil, goes through the button in the cap to the rotor, jumps to the terminals in the cap, goes through the plug wires to the plugs, jumps the gap in the plugs and then returns through the engine block to the metal distributor body and from there goes through a ground connection to the coil. Somewhere in that series chain of connections is a high resistance that isn't letting the voltage get to where it's supposed to go.
Did you check the black wire that comes out of the coil and goes under one of the screws that holds the coil? That's the ground wire for the coil secondary. It's shown in the picture in the link I posted previously:
http://forums.corvetteforum.com/1581679328-post6.html