If I have 12v+ at the top of the coil, why no spark? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

TIMSPEED · 11-02-2003, 03:47 AM

Huh...this damn truck's ignition stumps me DAILY! Again, it WILL NOT start. It cranks over like a mother bear, and has a FULL 12v+ at the HEI power Wire. Anyone wanna start the guessing? I've got an ENTIRELY brand new Distributor. I've had the coil and module tested MANY times. Last month, it did this same thing, and I replaced the cap/rotor, and it fired right up...again, I bought another cap/rotor and again it'll probably fire right up. Anyone wanna venture a guess WHY it keeps eating cap/rotor's? I absolutely HATE changing them, because they have those stupid L-clamps that NEVER want to sit right...

Blue Beard · 11-02-2003, 05:06 AM

Is the power wire a designed line on that year?

Tested for any shorts?

TIMSPEED · 11-02-2003, 07:07 AM

Quote:

Originally posted by Blue Beard
Is the power wire a designed line on that year?

Tested for any shorts?

I don't follow you. I had a friend hold the voltmeter on the HEI power wire that hooks to the Distributor cap, and as I cranked the truck, it held 12v+ the whole time without faltering...

Russell · 11-02-2003, 01:18 PM

I'm gonna guess that you're losing your spark somewhere in your plug cables... I replaced mine, and it was the best money I've spent on my truck yet... As for your caps not sitting right, put the cap on and rotate it till you feel it fall into place and not want to rotate anymore, then those little L clamps go in really nice and easy, and probally would extend the length of your cap's life. If it isn't your plug wires, then you are somehow getting tiny little cracks in your distro cap, and the electricity is going out of those fractures rather than up and out the pole. Just try to start the truck in complete darkness while looking under the hood, see if you can't find some sparks underthere....

*mike reeh* · 11-02-2003, 03:46 PM

12V to the distributor is the easy part.. its from there, on that is what you need to worry about.

pull one of the spark plug wires off of one of the spark plugs, and insert an extra spark plug.. ground the plug on the truck somewhere and have said buddy crank. check for spark. make sure you got a nice hot blue spark too..

if so, check timing, fuel delivery, and compression.

if not, check distributor.. If changing the cap magically fixed it last time, change it again and be real careful about what you do. Maybe there is a short in one of the wires coming off the coil, to the tach/batt terminal? maybe the ground is bad? do you have a good ground for the coil? is the area that the rotor button spring touches on the coil rusted or corroded? dont over tighten the coil & coil-cover bolts, it will tweak the distributor cap.. just snug em so that stuff isnt going to fall out.. Any condensation in the cap? how do the contacts look on the rotor and cap?

just a few ideas... just cuz everything is new dont mean it works! I tend to have more faith in old parts, sometimes...

keep us posted

mike

TIMSPEED · 11-02-2003, 06:14 PM

It MAY be my spark plug wires, although they're brand new...they also have a lifetime warranty, so I'll take those mofo's back and swap in the new ones.
We tried using a different spark plug, grounding it on the frame of the truck...still no spark.

soleeagle · 11-02-2003, 08:09 PM

I would check the ground myself first and check the 12 volt wire for a short also. My .02

TIMSPEED · 11-02-2003, 08:37 PM

What ground? The ground going from the coil to the HEI Module? Or the actual GROUND for the truck?

*1FaastC10* · 11-03-2003, 01:46 AM

pickup coil should be tested as well, you'll have to pull the dist for that one i believe

TIMSPEED · 11-03-2003, 06:10 AM

How could the pickup coil go bad so soon?

jimfulco · 11-04-2003, 02:18 AM

Next time it craps out on you, wiggle the wire connector & try it again. You may just have some corrosion at the connector.

TIMSPEED · 11-04-2003, 05:28 AM

Quote:

Originally posted by jimfulco
Next time it craps out on you, wiggle the wire connector & try it again. You may just have some corrosion at the connector.

Trust me, I've wiggled them ALL. I just don't freakin get it...

*1FaastC10* · 11-04-2003, 05:33 AM

Quote:

Originally posted by TIMSPEED
How could the pickup coil go bad so soon?

i dont know. how does a cam lose its lobes before its even full broken in? same thing... could be poor part quality, could be poor workmanship, or it could be an installer error. im not saying you did anything wrong, but the possibility is there.

Frank-id · 11-08-2003, 02:46 AM

The HEI read hi energy ignition is very robust and lives a long life.
The most critical componet in the hei system is the modual. This is the small electronic componet that has 4 wires entering it. This device is a super switch. The modual controls the coil output. Some parts store have a quickie tester. These moduals can last a very long time and some can fail in a couple weeks. What is the secret to the modual lasting a long time???????/ The modual MUST be kept COOL. It is cooled by coating the bottom of the modual with di-electric grease. With out any heat sink silicone/di-electric
grease, the unit overheats and fails.
After washing an engine with steam or water, sometimes WD40 is sprayed into the distributor. The WD40 can and does wash away the grease. No grease...unit quits........ The modual is the brains for the complete ignition system.......

Modual is black..on left side with wires and held with 2 hex screws. Special size.....

Frank-id · 11-08-2003, 02:48 AM

Quick picture

11-02-2003, 03:47 AM	#1
TIMSPEED Join Date: Jan 2003 Location: Modesto, CA Posts: 1,321	If I have 12v+ at the top of the coil, why no spark? Huh...this damn truck's ignition stumps me DAILY! Again, it WILL NOT start. It cranks over like a mother bear, and has a FULL 12v+ at the HEI power Wire. Anyone wanna start the guessing? I've got an ENTIRELY brand new Distributor. I've had the coil and module tested MANY times. Last month, it did this same thing, and I replaced the cap/rotor, and it fired right up...again, I bought another cap/rotor and again it'll probably fire right up. Anyone wanna venture a guess WHY it keeps eating cap/rotor's? I absolutely HATE changing them, because they have those stupid L-clamps that NEVER want to sit right... __________________ I have a few cars... See Them Here

11-02-2003, 05:06 AM	#2
Blue Beard Registered User Join Date: Jan 2003 Location: Washington State Posts: 8,834	Is the power wire a designed line on that year? Tested for any shorts? __________________ 1970 Chev CST 2003 Harley Fatboy 1975 Chevrolet Step Van 1956 Chev Bel Air 1977 Blazer 2WD For Sale $3000.00 1978 Blazer 2WD For Sale $7000.00 1978 Silverado 2005 Monte Carlo

11-02-2003, 01:18 PM	#4
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	I'm gonna guess that you're losing your spark somewhere in your plug cables... I replaced mine, and it was the best money I've spent on my truck yet... As for your caps not sitting right, put the cap on and rotate it till you feel it fall into place and not want to rotate anymore, then those little L clamps go in really nice and easy, and probally would extend the length of your cap's life. If it isn't your plug wires, then you are somehow getting tiny little cracks in your distro cap, and the electricity is going out of those fractures rather than up and out the pole. Just try to start the truck in complete darkness while looking under the hood, see if you can't find some sparks underthere.... __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

11-02-2003, 06:14 PM	#6
TIMSPEED Join Date: Jan 2003 Location: Modesto, CA Posts: 1,321	It MAY be my spark plug wires, although they're brand new...they also have a lifetime warranty, so I'll take those mofo's back and swap in the new ones. We tried using a different spark plug, grounding it on the frame of the truck...still no spark. __________________ I have a few cars... See Them Here

11-02-2003, 08:09 PM	#7
soleeagle Registered User Join Date: Sep 2003 Location: Shelbyville, Indiana Posts: 614	I would check the ground myself first and check the 12 volt wire for a short also. My .02 __________________ Chuck '85 Chevy Silverado 4X4 '91 Chevy 4X4 Suburban http://www.cardomain.com/memberpage/545941

11-02-2003, 03:46 PM	#5
mike reeh 5 day ban, learn to behave. Join Date: Nov 2002 Location: san diego, ca Posts: 684	12V to the distributor is the easy part.. its from there, on that is what you need to worry about. pull one of the spark plug wires off of one of the spark plugs, and insert an extra spark plug.. ground the plug on the truck somewhere and have said buddy crank. check for spark. make sure you got a nice hot blue spark too.. if so, check timing, fuel delivery, and compression. if not, check distributor.. If changing the cap magically fixed it last time, change it again and be real careful about what you do. Maybe there is a short in one of the wires coming off the coil, to the tach/batt terminal? maybe the ground is bad? do you have a good ground for the coil? is the area that the rotor button spring touches on the coil rusted or corroded? dont over tighten the coil & coil-cover bolts, it will tweak the distributor cap.. just snug em so that stuff isnt going to fall out.. Any condensation in the cap? how do the contacts look on the rotor and cap? just a few ideas... just cuz everything is new dont mean it works! I tend to have more faith in old parts, sometimes... keep us posted mike

11-02-2003, 08:37 PM	#8
TIMSPEED Join Date: Jan 2003 Location: Modesto, CA Posts: 1,321	What ground? The ground going from the coil to the HEI Module? Or the actual GROUND for the truck? __________________ I have a few cars... See Them Here

11-03-2003, 01:46 AM	#9
1FaastC10 Account Suspended Join Date: Oct 2002 Location: Elkhart, IN Posts: 6,400	pickup coil should be tested as well, you'll have to pull the dist for that one i believe

11-03-2003, 06:10 AM	#10
TIMSPEED Join Date: Jan 2003 Location: Modesto, CA Posts: 1,321	How could the pickup coil go bad so soon? __________________ I have a few cars... See Them Here

11-04-2003, 02:18 AM	#11
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	Next time it craps out on you, wiggle the wire connector & try it again. You may just have some corrosion at the connector.

11-08-2003, 02:46 AM	#14
Frank-id Registered User Join Date: Sep 2003 Location: Twin Falls, Idaho Posts: 73	No sparks The HEI read hi energy ignition is very robust and lives a long life. The most critical componet in the hei system is the modual. This is the small electronic componet that has 4 wires entering it. This device is a super switch. The modual controls the coil output. Some parts store have a quickie tester. These moduals can last a very long time and some can fail in a couple weeks. What is the secret to the modual lasting a long time???????/ The modual MUST be kept COOL. It is cooled by coating the bottom of the modual with di-electric grease. With out any heat sink silicone/di-electric grease, the unit overheats and fails. After washing an engine with steam or water, sometimes WD40 is sprayed into the distributor. The WD40 can and does wash away the grease. No grease...unit quits........ The modual is the brains for the complete ignition system....... Modual is black..on left side with wires and held with 2 hex screws. Special size..... __________________ Chevy stepper 400sb 350 turbo

11-08-2003, 02:48 AM	#15
Frank-id Registered User Join Date: Sep 2003 Location: Twin Falls, Idaho Posts: 73	HEI distributor Quick picture __________________ Chevy stepper 400sb 350 turbo

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