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Ignition problems- 305E V6
#1394187 Mon Jan 25 2021 05:20 AM
Joined: Jan 2021
Posts: 49
J
Jimmy66 Offline OP
'Bolter
Hello! New member here. I’m a guitar builder and repair man, not a mechanic by any means. I had the chance to get the truck we camped in as a kid from my dad and I took it, so bare with my ignorance, please I recently revived my family’s 1966 GMC 3/4 ton pick up, (with a cab over open road camper and all). It hadn’t run in about 33 years. Worked on it over the summer, got it running and drove it the short 5 minutes from my parents to my house. It made it fine. I was replacing things as I went, carb rebuild, fuel pump and fuel filter, thermostat, master cylinder, bled breaks, etc. I was just taking it around my neighborhood every few days to keep it moving and one day it started stalling out on me and acting like it was starved for fuel.I barely made it home.
Since then it tries, but has not started. My first thought was I didn’t clean fuel tank well enough, so I’ve replaced the fuel tank and all the rubber line, as well as blowing out steel lines with compressed air, put an in line fuel filter, carb is getting gas. So I did a tune up, all new plugs, points, coil, condenser, rotor, wires, cap. Still wouldn’t start. I’m not getting blue spark, orange weak spark. Just installed high power alternator, and pertronix electronic ignition, and came across this resistor wire! Is it possible this has been my issue all along? I’m going to install the pertronix power relay that bypasses the resistor wire, it’s on its way. Any input would be greatly appreciated. I’m very much a novice. Thanks! - Jimmy


Jimmy Deveney
‘66 GMC 3/4 ton pick up
4 speed manual
305E V6
Re: Ignition problems- 305E V6
Jimmy66 #1394212 Mon Jan 25 2021 01:03 PM
Joined: May 2007
Posts: 1,546
'Bolter
Welcome Jimmy. Those camper trucks are good to save. Likely some extra options on that truck. We need pictures.

We will see what the engine experts have to say, but it sounds like you are hitting the right chords.
Confirm you cleaned the small filter in the input to the carb. My first thought is fuel, but if you cleaned and checked the tank, lines and carb then we shortly can check that off the list.


HB

1966 Chevrolet K-10
Flappy Fenders
In the Stovebolt Gallery [stovebolt.com]
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1962 Chevrolet C10
1962 Suburban
Re: Ignition problems- 305E V6
Jimmy66 #1394220 Mon Jan 25 2021 01:49 PM
Joined: Apr 2005
Posts: 9,675
Grease Monkey, Moderator General Truck Talk & Greasy Spoon
Take everything off that is associated with Pertronix. Go back to original or get a GM HEI with the coil in the cap. Some have good results with Pertronix but a significant amount of folks don’t. Weak orange spark won’t do it.


Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne 4dr 230 I-6 one owner (I’m #2) “Emily”
‘39 Dodge Businessmans Coupe “Clarence”



"I fought the law and the law won" now I are a retired one!
Support those brave men/women who stand the "Thin Blue Line"! Hug a cop!
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Re: Ignition problems- 305E V6
Jimmy66 #1394232 Mon Jan 25 2021 02:48 PM
Joined: Jan 2021
Posts: 49
J
Jimmy66 Offline OP
'Bolter
Thanks for the replies. To be fair to the Pertronix, I had weak orange spark before I put it in. I will wait for the relay to get here and try it, if that works, i will assume the resistor wire was my problem. If not, I will remove it all. I appreciate it. I have a couple knowledgeable friends here in Albuquerque, but I’m mostly experimenting, learning as I go.👍🏻


Jimmy Deveney
‘66 GMC 3/4 ton pick up
4 speed manual
305E V6
Re: Ignition problems- 305E V6
Jimmy66 #1394238 Mon Jan 25 2021 03:32 PM
Joined: Jan 2021
Posts: 49
J
Jimmy66 Offline OP
'Bolter
Here’s a picture of the truck. Unfortunately, my parents used the camper as storage for years, and there were leaks they didn’t know about. There is quite a bit of water damage and mold, so I am probably going to get rid of it once the truck is running, and just keep the truck.

Attached Files
07162E39-AA40-43DC-8C90-5796C5E7C11C.jpeg (286.43 KB, 260 downloads)

Jimmy Deveney
‘66 GMC 3/4 ton pick up
4 speed manual
305E V6
Re: Ignition problems- 305E V6
Jimmy66 #1394243 Mon Jan 25 2021 04:08 PM
Joined: Feb 2004
Posts: 22,198
H
'Bolter
Ditto on the "trash the Pertronix" advice. I'm not aware of a factory HEI distributor that will replace a 305 V6 distributor without some pretty extensive machining, but there are two types of Pertronix units- - - -the ones that have failed, and the ones that are getting ready to! A hot blue spark is only necessary if you want to replace distributor caps and rotors on a regular basis. If you're using resistor type ignition wires (a good idea) a normal spark will be orange/yellow looking.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Ignition problems- 305E V6
Jimmy66 #1394272 Mon Jan 25 2021 07:52 PM
Joined: May 2005
Posts: 8,089
B
Sir Searchalot
The dreaded "replaced everything but still won't start". It is true there is no drop-in HEI for these motors.

They use a bypass resistive ignition system as do most 12V points motors of the day.

I will have about 5-10 questions when you are ready. Test the battery or get a new one pretty quick.

Take off the camper and take off the spare from front before I go nuts smile. Hopefully they kept the tailgate. Keep the mirrors, they can be worth money. This is a really good truck with a good motor. Long lasting, powerful motor. I like them for a daily driver truck. But the motor is a boat anchor. I say that with all respect to GMC engineers. The motor is a design masterpiece. Except it's maxed out at 3800 RPM. Approaching 900 lb weight without trans.
60-66 GMC's are fairly rare, especially if it has factory options. Yours seems to be a non deluxe variety. That's OK. The originality of your truck makes it very valuable to some folks, so keep that in mind with all your changes. The GMC crowd is very loyal. 1966 is a premium year. Last year for that body style.

Pertronix is OK. Not necessary, but OK. The newer II and III are better than the old Ignitor I. THE "POWER RELAY" IS A 100% SCAM. If it works, it means you did not install the Pertronix correctly in the first place.

Last edited by bartamos; Sat Feb 27 2021 06:09 AM.

Watch out for careful drivers!!!
I'm away on an ego trip. Will be back on Feb 30.
I'm not an Auto Mechanic, but I play one on TV.
I charge $0.02 for every opinion and I take Paypal.
Plan B is always better than plan A, by definition.
You can't teach a new dog old tricks.


Re: Ignition problems- 305E V6
bartamos #1394315 Tue Jan 26 2021 12:05 AM
Joined: Jan 2021
Posts: 49
J
Jimmy66 Offline OP
'Bolter
Thanks Bartamos-

Battery is new, 4 months old, and is reading 12.6v on a meter.

Tailgate and mirrors are long gone. It was purchased with the camper on it from an Albuquerque dealer who packaged them that way. Had badges made for the side that say "Camper Liner". Dan Ely Buick.

I will take the spare off when I take the camper off. Thats one of the old split rims. It has new wheels and tires now.

The Pertronix I installed is a II.

So far I have not changed anything that can't be changed back to original, and I'm keeping everything I take out for the time being.

Fire away with your questions.


Jimmy Deveney
‘66 GMC 3/4 ton pick up
4 speed manual
305E V6
Re: Ignition problems- 305E V6
Jimmy66 #1394378 Tue Jan 26 2021 10:26 AM
Joined: May 2005
Posts: 8,089
B
Sir Searchalot
OK Jimmy, lets get her figured out. You said you had "yellow spark" before and after the Pertronix. Please be sure to answer every question carefully and thoroughly.
1. You said new coil. When was new coil added? During the points ignition testing or when Pertronix was installed? Did this new coil come with the Pertronix or is it one they recommended? or is it just a generic coil? What words appear on it? What do you know about it's specs?
2. What did you do with the resistance wire? What, if anything, is it wired to right now?
3. Are you saying the starter turns over the motor at a good rate? Is the yellow spark seen across a removed spark plug during cranking or ?
4. Did you, at any point, take out the distributor?
5. Did you add any "ignition" wires? or starter wires? or any wires?
6. What do the Pertronix instructions say about the resistance wire? Did you adjust the gap on the Pertronix to .030 for sure.
7. Is there absolutely no fire when cranked? No backfire at carb or tail pipe? No attempt to start at all? No sputter or odd noise?
8. Can you post good, well lit, clear pics of the distributor and it's wires before you disturb them or add this "relay"? Can you describe exactly how the Pertronix unit and the ignition coil are wired now?
9. If there is a special Pertronix for V6, did you get the correct unit? What is the Pertronix part number?

Feel free to post any other pics of the motor.


Watch out for careful drivers!!!
I'm away on an ego trip. Will be back on Feb 30.
I'm not an Auto Mechanic, but I play one on TV.
I charge $0.02 for every opinion and I take Paypal.
Plan B is always better than plan A, by definition.
You can't teach a new dog old tricks.


Re: Ignition problems- 305E V6
bartamos #1394424 Tue Jan 26 2021 04:34 PM
Joined: Jan 2021
Posts: 49
J
Jimmy66 Offline OP
'Bolter
1. You said new coil. When was new coil added?
I added a new coil during points testing, it was an OE Driveworks from advance auto, part #26189
I tried swapping it back for original coil, and there was no change.
I have since installed the Pertronix flamethrower coil to go with Ignitor II


2. What did you do with the resistance wire? What, if anything, is it wired to right now?
It is still wired in place, to positive on coil, and goes into wiring harness. I believe it goes to starter and to plug in firewall. I have not tried turning it over more than once since Pertronix, because wire is not yet bypassed. I tested new alternator, just to make sure it was in correctly.

3. Are you saying the starter turns over the motor at a good rate? Is the yellow spark seen across a removed spark plug during cranking or ?
Yes, it sounds like it is turning in over at a good rate, although my only other thought of a culprit is the starter. Yellow spark seen from a spark plug wire removed at cranking.

4. Did you, at any point, take out the distributor? no

5. Did you add any "ignition" wires? or starter wires? or any wires? no

6. What do the Pertronix instructions say about the resistance wire?
Instructions said to remove resistance wire or install relay. I opted for relay incase I had to put it back, and because I don't want to slice up the wiring harness.

Did you adjust the gap on the Pertronix to .030 for sure? as best I can tell, I used the feeler gauge.

7. Is there absolutely no fire when cranked? No backfire at carb or tail pipe? No attempt to start at all? No sputter or odd noise?
no backfire, occasional sputter like it wants to start.

8. Can you post good, well lit, clear pics of the distributor and it's wires before you disturb them or add this "relay"?
we got a snow storm last night, so as soon as it warms up this afternoon, I will take pictures.

Can you describe exactly how the Pertronix unit and the ignition coil are wired now?
I followed Pertronix directions exactly, their leads from unit come to ground and positive posts on coil, and the yellow wire and resistance wire are also on positive post for coil. inside distributor there is a ground to plate, and the unit itself.

9. If there is a special Pertronix for V6, did you get the correct unit? What is the Pertronix part number?
Pertronix part number is 36-2945 Ignitor II for 6 cylinder, I didn't think of that, I suppose it could be for inline 6?

Feel free to post any other pics of the motor.
Albuquerque snow doesn't last long, I'll update with some pics later today.


Jimmy Deveney
‘66 GMC 3/4 ton pick up
4 speed manual
305E V6
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