The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > General Truck Forums > Electrical

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 03-07-2017, 05:35 PM   #1
jricharc
Registered User
 
Join Date: Jun 2016
Location: Manassas, VA
Posts: 68
HEI wiring questions

So I recently bought an '86 C10 that had a late 70's 350 dropped in it. I just replaced the carburetor with a brand new summit brand carb along with replacing the distributor with an original that was pulled from a running vehicle. I replaced the entire distributor because the original had red dust all inside of it and I got a good deal on the "new" one. I also have a new cap, rotor and coil and the issue I am having is that the truck will intermittently not start due to no spark, I have it nailed down to the wiring in the distributor area. It is either the wires running to the distributor or the wires inside because if I move the wires around or tap the top of the cap it fires right up.

I just bought a new PICO wiring connector to replace the older one running from the ignition but all the ones I see just have one wire for the ignition, however mine has two... So does anyone know what the second wire might be and is it needed? I don't have a tach in the truck.

Here is what I bought:


Here is my current setup:
__________________
1986 C10 LWB 350
1970 C10 LWB 350 - Sold
jricharc is offline   Reply With Quote
Old 03-07-2017, 09:35 PM   #2
88Ironduke
Registered User
 
Join Date: Jul 2010
Location: Willingboro, NJ
Posts: 457
Re: HEI wiring questions

First thought is ignition module. They get hot and then they go intermittent resulting in no spark. I keep a spare for my 72' with late 70's HEI distributor. You never know when they will let go.

As for the pigtail, you have the right one but unless the current connector isn't staying in place due to age/brittle plastic I would not mess the OEM unless you really mean it. Next time you get hot start/no spark I would be checking for 12 volts DC at the large pink wire feeding the "bat" side of the distributor. Ignition "run" you'll get 12 volts DC at that wire. Get a helper and crank the truck over, key to "start" you should have 12 volts DC thru the start cycle. If either is not present your problem is further back in the system. possibly

Paul
__________________
Retired USAF - No rockets, no mortars, no bad guys shooting...No stress!!!

My Build Thread: Project 72' Green
http://67-72chevytrucks.com/vboard/s...d.php?t=587932
88Ironduke is offline   Reply With Quote
Old 03-09-2017, 12:46 PM   #3
Dead Parrot
Registered User
 
Join Date: Aug 2012
Location: Oklahoma City, OK
Posts: 774
Re: HEI wiring questions

Off the cuff guess for the second wire is something to do with either a computer sensor or emission control that needed power when the ignition was powered on. Guessing those are long gone now.

I have an Accel distributor that looks very similar to that one. Only needs the one power wire. Double check the little button in the top of the cap. Also, IIRC, there is a ground strap inside under the coil that you need to make sure is making a good connection.

Make sure to clean the power connector. Its 31 years old and might have some corrosion or left over grease that is causing a poor connection.
Dead Parrot is offline   Reply With Quote
Old 03-09-2017, 05:14 PM   #4
Boog
primer is finer
 
Boog's Avatar
 
Join Date: Mar 2001
Location: Searcy, Ark. USA
Posts: 6,753
Re: HEI wiring questions

It would be highly unlikely GM piggy backed something onto the ignition power supply wire so i would follow that wire from the dist cap and see where it goes. Hei needs a solid 12 volts to operate at maximum.
I have heard of someone tapping into the dist feed wire to power an electric choke but that's not a good idea.
__________________
Boog
69 Chevy stepside, 358/T350, 4.10 posi, 4.5/4 drop, rallys, poboy driver
09 Yukon SLT 4wd, 06 GMC crewcab Z71 5.3, 4.10
All GM..'nuff said,
Member of Jr Nation 88
Boog is offline   Reply With Quote
Old 03-10-2017, 12:00 PM   #5
jricharc
Registered User
 
Join Date: Jun 2016
Location: Manassas, VA
Posts: 68
Re: HEI wiring questions

Thanks, I do have the ground strap in the cap and everything with coil is tight. I didn't think there should be two wires going into the ignition area so I am going to trace that wire and make sure I have one good wire getting 12V with the key and see if that helps at all.
__________________
1986 C10 LWB 350
1970 C10 LWB 350 - Sold
jricharc is offline   Reply With Quote
Old 03-10-2017, 06:08 PM   #6
ray_mcavoy
Registered User
 
Join Date: Nov 2009
Location: Sherman, ME
Posts: 1,859
Re: HEI wiring questions

Actually, GM did piggyback off the ignition power supply on some of these trucks to power the ESC (Electronic Spark Control) module. Trucks that originally had ESC will have the regular pink wire feeding power to the HEI. An orange fusible link wire is joined in at the HEI connector. The other end of the orange fusible link splices to a pink wire that goes through a grommet in the firewall along with 6 or 7 other wires that lead to the ESC module mounted up under the dash near the glovebox.
ray_mcavoy is offline   Reply With Quote
Old 03-10-2017, 06:28 PM   #7
jricharc
Registered User
 
Join Date: Jun 2016
Location: Manassas, VA
Posts: 68
Re: HEI wiring questions

Quote:
Originally Posted by ray_mcavoy View Post
Actually, GM did piggyback off the ignition power supply on some of these trucks to power the ESC (Electronic Spark Control) module. Trucks that originally had ESC will have the regular pink wire feeding power to the HEI. An orange fusible link wire is joined in at the HEI connector. The other end of the orange fusible link splices to a pink wire that goes through a grommet in the firewall along with 6 or 7 other wires that lead to the ESC module mounted up under the dash near the glovebox.
Thanks, that must be what that wire is, I will just get a good 12V source and run that so I know what I have is good. I think when the 350 was dropped in the wiring was spliced to make it work and some connections may be loose.
__________________
1986 C10 LWB 350
1970 C10 LWB 350 - Sold
jricharc is offline   Reply With Quote
Old 03-13-2017, 10:59 AM   #8
Boog
primer is finer
 
Boog's Avatar
 
Join Date: Mar 2001
Location: Searcy, Ark. USA
Posts: 6,753
Re: HEI wiring questions

I stand corrected. Thank you Ray.
__________________
Boog
69 Chevy stepside, 358/T350, 4.10 posi, 4.5/4 drop, rallys, poboy driver
09 Yukon SLT 4wd, 06 GMC crewcab Z71 5.3, 4.10
All GM..'nuff said,
Member of Jr Nation 88
Boog is offline   Reply With Quote
Old 04-10-2017, 07:14 PM   #9
'68OrangeSunshine
Senior Member
 
'68OrangeSunshine's Avatar
 
Join Date: Feb 2002
Location: Tucson, AZ USA
Posts: 3,930
Re: HEI wiring questions

Yeah. Module.
__________________


Every 25 years I like to rebuild that 292, whether it needs it or not.
'68OrangeSunshine is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

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

Forum Jump


All times are GMT -4. The time now is 12:50 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright 1997-2013 67-72chevytrucks.com