6066 (1960-1966) GMC Truck Club Bitcoin now accepted here! 
Pay Dues
Pay Dues or become a Site Supporter
 



Go Back   6066 (1960-1966) GMC Truck Club > 6066 GMC Truck Club Forum > Interiors, Dash, Lights and Electrical
#Sponsored

Interiors, Dash, Lights and Electrical Everything Inside

Reply
 
Thread Tools
  #1  
Old July 23rd, 2024, 03:06 PM
Harleyq Harleyq is offline
Member
 
Join Date: Oct 2022
Location: Medford, Or.
Truck: '66 gmc pu
Posts: 45
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 24
Harleyq is on a distinguished road
Default No spark at plugs

Hi folks, am beyond stumped here. Have 12 volts to distributor, but nothing to plugs. Have replaced dist cap and icm, coil ohms out perfectly. Normally have this thing up and going in 15 minutes. What am i missing? Rotor is good, distributor spins just fine but no spark. Any suggestions? It seems w8th 12 to the distributor, coil is good and new icm, i should have spark at plugs. This is an hei distributor on a gm 350 that was dropped 8n before I got her. Thank you in advance for any suggetions.
Reply With Quote
  #2  
Old July 23rd, 2024, 05:46 PM
James James is offline
-= Extreme Supporter =-
 
Join Date: Jun 2013
Location: Greer, SC
Truck: 1964 GMC 1500 2wd
Age: 69
Posts: 449
Thanks: 8
Thanked 4 Times in 3 Posts
Rep Power: 206
James will become famous soon enoughJames will become famous soon enoughJames will become famous soon enough
Default Re: No spark at plugs

Is the carbon button on the inside of the cap there? If it is missing, the spark will not reach the distributor rotor or spark plugs. This can cause the coil to burn itself into.

Just a side note and it might not be a problem. With the ignition on and with 12 volts feeding the distributor, measure the voltage between the distributor housing and the engine ground. Should be zero volts (if a voltage {any amount of voltage} is present it is not grounded). If the distributor housing is not grounded, no sparks. The ICM is grounded through the base plate to the vacuum advance plate and then the housing. Only apply a thin layer of heat sinking compound to the ICM base plate, nothing should be insulating the ICM base plate to ground. Then secure it to the distributor vacuum advance plate.

Another way this can be check by removing the cap (and all of the wire connectors connecting to the cap and set it aside on the bench or toolbox.) and place the meter on 200Ω scale, measure between the ICM base plate and to the vacuum advance plate, then to distributor housing, and to the engine. Should be less than .5Ω resistance (don't forget to short the leads together first to determine what leads resistance is and substract that from your measurements).

If everything check good, the the ICM is at fault. I don't know if the auto parts store can still check the ICM (with a ICM tester) like they used to do years ago. This might also be worth a try.
Reply With Quote
  #3  
Old July 23rd, 2024, 05:51 PM
James James is offline
-= Extreme Supporter =-
 
Join Date: Jun 2013
Location: Greer, SC
Truck: 1964 GMC 1500 2wd
Age: 69
Posts: 449
Thanks: 8
Thanked 4 Times in 3 Posts
Rep Power: 206
James will become famous soon enoughJames will become famous soon enoughJames will become famous soon enough
Default Re: No spark at plugs

Another though. If you are not using a tach output from the distributor, make sure you plug the power into the correct distributor B+ terminal. Connecting it to the tach output will provide no sparks.
Reply With Quote
  #4  
Old July 24th, 2024, 01:25 AM
Harleyq Harleyq is offline
Member
 
Join Date: Oct 2022
Location: Medford, Or.
Truck: '66 gmc pu
Posts: 45
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 24
Harleyq is on a distinguished road
Default Re: No spark at plugs

Thank you for the advice, I think that is the one thing I haven't checked ground from engine. Will check that forthwith and see what we have. It was running fine, started fine and had just left when it died and thos is where we are at, no start, no soark.
Reply With Quote
  #5  
Old July 24th, 2024, 01:35 AM
Harleyq Harleyq is offline
Member
 
Join Date: Oct 2022
Location: Medford, Or.
Truck: '66 gmc pu
Posts: 45
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 24
Harleyq is on a distinguished road
Default Re: No spark at plugs

The button is therenand free, I made sure it was there and free and making good contact. Replaced the icm already. Not sure about the testing of...
Reply With Quote
  #6  
Old July 24th, 2024, 08:39 PM
Harleyq Harleyq is offline
Member
 
Join Date: Oct 2022
Location: Medford, Or.
Truck: '66 gmc pu
Posts: 45
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 24
Harleyq is on a distinguished road
Default Re: No spark at plugs

Still have no spark, pulled distributor gear is good turns freely and wires to icm are good. What can I be missing?
Reply With Quote
  #7  
Old July 24th, 2024, 10:29 PM
AZKen's Avatar
AZKen AZKen is offline
Senior Member
 
Join Date: Jul 2014
Location: AZ
Truck: 6066GMC
Posts: 1,634
Thanks: 0
Thanked 2 Times in 2 Posts
Rep Power: 524
AZKen is just really niceAZKen is just really niceAZKen is just really niceAZKen is just really niceAZKen is just really niceAZKen is just really nice
Default Re: No spark at plugs

What year is the motor
Reply With Quote
  #8  
Old July 24th, 2024, 10:37 PM
Prowbar Prowbar is offline
Senior Member
 
Join Date: Dec 2020
Location: Friesland, the Netherlands
Truck: 1965 GMC 1500, 478 V6, SM420
Posts: 432
Thanks: 8
Thanked 8 Times in 7 Posts
Rep Power: 198
Prowbar is a jewel in the roughProwbar is a jewel in the roughProwbar is a jewel in the roughProwbar is a jewel in the roughProwbar is a jewel in the roughProwbar is a jewel in the rough
Default Re: No spark at plugs

Are you using the stock resistor wire or a separate wire from the ignition switch to power the HEI? And did you measure the voltage with a test light or a multimeter?

Temporarily jump the ground from the distributor housing to the negative terninal of the battery to confirm a working ground I'd suggest.

Otherwise pull the dist and test it on the bench for spark.
Reply With Quote
  #9  
Old July 25th, 2024, 04:02 AM
Harleyq Harleyq is offline
Member
 
Join Date: Oct 2022
Location: Medford, Or.
Truck: '66 gmc pu
Posts: 45
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 24
Harleyq is on a distinguished road
Default Re: No spark at plugs

How would I benc test, haven't had the opportunity to do so yet. ...

It is a 78 gm 350 height dist. Have also changed the magnetic pickup with no change...
Reply With Quote
  #10  
Old July 25th, 2024, 04:05 AM
Harleyq Harleyq is offline
Member
 
Join Date: Oct 2022
Location: Medford, Or.
Truck: '66 gmc pu
Posts: 45
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 24
Harleyq is on a distinguished road
Default Re: No spark at plugs

We have done both, ran wire from battery to dist no change. Tested v going in at 12.9 dropped to -9 when cranking. At a loss for what it could be, the dist is practically rebuilt...
Reply With Quote
Reply

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Re: Spark Plugs Archiver Previous Forum Posts 0 May 23rd, 2009 03:05 AM
Re: Spark Plugs Archiver Previous Forum Posts 0 May 21st, 2009 05:43 AM
Spark plugs Archiver Previous Forum Posts 0 May 31st, 2006 01:49 AM
Spark Plugs. Archiver Previous Forum Posts 0 October 6th, 2005 01:23 AM
What spark plugs? Archiver Previous Forum Posts 0 July 7th, 2003 01:28 AM


All times are GMT +1. The time now is 07:27 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2013, Jelsoft Enterprises Ltd 771728135336|1726943245|0