SBC sparking on 5 cylinders only. - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans Advertise
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 07-15-2019, 10:51 AM
Registered User
 
Join Date: May 2019
Location: Bradenton, FL
Age: 77
Posts: 42
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
SBC sparking on 5 cylinders only.

Hey guys and gals, my sbc 350 is absolutely driving me into the looney ward. Ive been dealing with a progressive no-spark problem for months. With previous dizzy engine would run very rough and die. Dropped in a HEI DUI unit and engine would crank, try to start -- but no dice.


Then it would crank only. No spark in any cylinder except for a very weak spark in #4. Pulled #1 plug and it was black with soot from cranking and stumbling I suppose ; unusual on a new set of Iridium plugs.


I installed a new ignition module and no difference. Pulled the DUI unit and replaced it with a good, standard HEI and got it to run, although badly. It was obviously dropping cylinders.


Checked spark and it's sparking on cylinders 1-3-5-7 (left bank), and only #4 on the right bank.


It has new wires, and there's no mix-up. Cap and rotor look fine.


The winning answer gets a 24-pack of your choice of beer. Really!

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 07-15-2019, 10:59 AM
Registered User
 
Join Date: Apr 2007
Posts: 12,581
Wiki Edits: 0

Thanks: 218
Thanked 1,194 Times in 946 Posts
First thing to do is to check the voltages going into the ignition system. If undervolt you will get a lot of what you are seeing.

Bogie
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 07-15-2019, 11:12 AM
Registered User
 
Join Date: May 2019
Location: Bradenton, FL
Age: 77
Posts: 42
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Yes, Bogie ... paramount. I checked the voltage along the way using the ohm meter, and it registered a solid 12v at the ignition and dizzy, and 10v when cranking. However, I will check it again for sure; it hasn't been checked lately.
Reply With Quote Quick reply to this message
 
  #4 (permalink)  
Old 07-15-2019, 11:39 AM
Registered User
 
Join Date: Dec 2013
Location: VT
Posts: 702
Wiki Edits: 0

Thanks: 1
Thanked 131 Times in 100 Posts
Run a separate wire from battery + to power input on HEI. This will bypass all wiring and Ig switch. You'll need to disconnect the wire to shut down engine. Pull spark plugs and put in a set of dry properly gapped plugs. Used plugs are OK. Check spark plug wire Resistance with an ohm meter. Write down the resistance of each plug wire. You'll need the high scale of the meter around 20,000 ohms. Obviously the longer wires will have higher resistance. You're looking for wires that are way out of the range of reasonable resistance. I know you said new plug wires. Lately I've seen bad NEW plug wires. Double check plug wires are in proper firing order. When you get it running, even poorly, spray plug wires and distributor cap with water from a spray bottle like a Windex bottle. Look for spark arcing at wires or cap. Is this a new or newly rebuilt engine and possibly the valves are adjusted way to tight? Let us know what happens. Beer is good.
Reply With Quote Quick reply to this message
The Following User Says Thank You to '48 Austin For This Useful Post:
Rip VW (07-15-2019)
  #5 (permalink)  
Old 07-15-2019, 12:04 PM
silver74vette's Avatar
Registered User
 
Join Date: Feb 2018
Posts: 165
Wiki Edits: 0

Thanks: 37
Thanked 29 Times in 22 Posts
Check the ground strap to the engine/ transmission. You can try grounding with jumper cables from each head to make sure you have a strong ground.
Reply With Quote Quick reply to this message
The Following User Says Thank You to silver74vette For This Useful Post:
Rip VW (07-15-2019)
  #6 (permalink)  
Old 07-15-2019, 12:46 PM
Registered User
 
Join Date: May 2019
Location: Bradenton, FL
Age: 77
Posts: 42
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
I'll perform all of these steps eventually, and thank you. First though, I'm concerned with the lack of spark in those 3 cylinders (2-6-8). I'm checking spark of course at the boots. I will check the wire resistance, and look for spark arching while cranking. I have a 4-cylinder spark tester and it works great; showing spark on the four cylinders 1-3-5-7.


To pull and replace all the plugs is a 3-4 hour+ exercise in frustration. Because this is a 22' boat engine (in a very tight-space center console), the combination of the Vortec heads and the new Mercruiser exhaust risers, you can't even see the plugs -- must blindly reach under to find them -- and some have maybe 1/4-inch clearance. I have to use three different tools to get'm in and out.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 07-15-2019, 01:40 PM
Rip VW's Avatar
Registered User
 

Last journal entry: This thread is officially Kaput as of 11/07/2017
Join Date: Jan 2015
Location: Coastal ,Washington
Age: 65
Posts: 867
Wiki Edits: 0

Thanks: 3,230
Thanked 938 Times in 530 Posts
Quote:
Originally Posted by silver74vette View Post
Check the ground strap to the engine/ transmission. You can try grounding with jumper cables from each head to make sure you have a strong ground.
X two from here. if it ran fine on the stand and crappy in the car Something is not right. grounds are usually the first thing forgotten when doing a engine swap.

Ground to body and chassis. 12 volts jumped from + on bat and if your dist is good and wired are good and plugs are good, Do you have Fuel to the motor? it should light off then.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 07-15-2019, 02:03 PM
36 sedan's Avatar
Registered User
 
Join Date: Apr 2016
Location: American Canyon, CA
Posts: 1,089
Wiki Edits: 0

Thanks: 641
Thanked 315 Times in 251 Posts
Quote:
Originally Posted by LARRYOWEN View Post
Pulled #1 plug and it was black with soot from cranking and stumbling I suppose ; unusual on a new set of Iridium plugs
Plugs are fouled from fuel or oil, if your using them to check spark youíll probably not see it because itís grounding inside the plug.
You may have a flooding carburetor causing your problem
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 07-15-2019, 03:10 PM
Registered User
 
Join Date: May 2019
Location: Bradenton, FL
Age: 77
Posts: 42
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
The plugs and carb are not relevant to this exercise -- only trying to get spark in cylinders 2-6-8. Spark is good on cylinders 1-3-5-7 (left bank), and only #4 on the right bank. I'm using a pro 4-plug spark tester hooked to the spark plug wire boots and a ground to the engine. No need to have engine running, just cranking.



I have verified grounds are solid.



And thanks, Rip, but the Blueprint 350 long block engine was fired up for the first time after installation about 4 months ago. Its been a nut buster ever since.



(the rest of the suggestions are top notch for when I get it running again, however badly).


Larry
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 07-15-2019, 04:49 PM
36 sedan's Avatar
Registered User
 
Join Date: Apr 2016
Location: American Canyon, CA
Posts: 1,089
Wiki Edits: 0

Thanks: 641
Thanked 315 Times in 251 Posts
Quote:
Originally Posted by LARRYOWEN View Post
The plugs and carb are not relevant to this exercise
JMHO, and just trying to help, not trying to insult, disrespect or anything else, but, nothing is ill-relevant. Black sooty plugs are a symptom, just like everything else, usually black sooty is a sign of PLUGS firing a rich fuel mixture, plugs that don't fire are usually wet.

But carrying on to other things, try your spark plug tester at the cap to see if wires are grounding out, sometimes rodents chew on the spark plug wires where you can't see it (and they can do it overnight). If the tester reads the same cylinders are dead at the cap as it does on the wire ends, check your cap and rotor even if it's new. And, make sure your module is phased correctly.
Reply With Quote Quick reply to this message
The Following User Says Thank You to 36 sedan For This Useful Post:
Rip VW (07-16-2019)
  #11 (permalink)  
Old 07-15-2019, 07:25 PM
johnsongrass1's Avatar
Race it, Don't rice it!
 
Join Date: Jul 2002
Location: Columbia, Mo
Age: 43
Posts: 7,076
Wiki Edits: 0

Thanks: 112
Thanked 746 Times in 612 Posts
Sounds like it’s something under the cap to me.
The rotor, tang, button, crossfire, tracking, something like that.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 07-16-2019, 06:09 AM
Registered User
 
Join Date: Dec 2013
Location: VT
Posts: 702
Wiki Edits: 0

Thanks: 1
Thanked 131 Times in 100 Posts
On the cylinders that are not running/sparking, disconnect the plug wire at the plug and plug in a known good plug and lay it on the valve cover. Check for spark with your tester and at plug gap. If you get spark, the plug in the cylinder head is badly fouled and that's why it won't run on that cylinder. Fouled plugs can be from extremely rich or flooding situation caused by closed choke or very high fuel pressure that would overpressure the float needle and seat and flood the engine with fuel. Check fuel pressure at carb. Should be about 4.5 to 5.5 PSI. Certainly no more than 6 PSI. Are you running an electric fuel pump? If so you may need a pressure regulator to get pressure down. OR a bunch of dirt may have been pumped into carb and got caught between needle and seat not allowing fuel flow to be shut off by the needle and seat therefore flooding the engine. Let us know what happens.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 07-16-2019, 08:59 AM
2001Blazer4x4's Avatar
Redneck Professional
 
Join Date: Jan 2015
Location: Indiana
Posts: 902
Wiki Edits: 0

Thanks: 114
Thanked 193 Times in 162 Posts
Need to back away for a minute from the idea that you have no spark. How sure are you?? Enough to hold the end of the plug wire?

Really sounds like badly fouled plugs from overly rich mix to me (all the way back to the beginning of your story with original distributor).
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 07-16-2019, 09:58 AM
Registered User
 
Join Date: May 2019
Location: Bradenton, FL
Age: 77
Posts: 42
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by 36 sedan View Post
JMHO, and just trying to help, not trying to insult, disrespect or anything else, but, nothing is ill-relevant. Black sooty plugs are a symptom, just like everything else, usually black sooty is a sign of PLUGS firing a rich fuel mixture, plugs that don't fire are usually wet.

But carrying on to other things, try your spark plug tester at the cap to see if wires are grounding out, sometimes rodents chew on the spark plug wires where you can't see it (and they can do it overnight). If the tester reads the same cylinders are dead at the cap as it does on the wire ends, check your cap and rotor even if it's new. And, make sure your module is phased correctly.
Excellent ideas, especially to test spark at the cap. Once the engine eventually idles and fires on all 8, I think the sooty plug issue will go away with a new set of plugs. If not, I will check fuel delivery and pressure, adjust carb settings -- it's a rebuilt Quadrajet and could very well be running rich -- and use the advice all of you have generously given me.



And 36sedan, please never hesitate to be frank. You will never hurt my feelings when trying to help.
Reply With Quote Quick reply to this message
The Following User Says Thank You to LARRYOWEN For This Useful Post:
36 sedan (07-16-2019)
  #15 (permalink)  
Old 07-16-2019, 11:30 AM
Registered User
 
Join Date: May 2019
Location: Bradenton, FL
Age: 77
Posts: 42
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by '48 Austin View Post
Run a separate wire from battery + to power input on HEI. This will bypass all wiring and Ig switch. You'll need to disconnect the wire to shut down engine. Pull spark plugs and put in a set of dry properly gapped plugs. Used plugs are OK. Check spark plug wire Resistance with an ohm meter. Write down the resistance of each plug wire. You'll need the high scale of the meter around 20,000 ohms. Obviously the longer wires will have higher resistance. You're looking for wires that are way out of the range of reasonable resistance. I know you said new plug wires. Lately I've seen bad NEW plug wires. Double check plug wires are in proper firing order. When you get it running, even poorly, spray plug wires and distributor cap with water from a spray bottle like a Windex bottle. Look for spark arcing at wires or cap. Is this a new or newly rebuilt engine and possibly the valves are adjusted way to tight? Let us know what happens. Beer is good.
I love Austins! I was 6 years old when your chassis was built, and my dad said it was his most preferred auto, post WWII.



I have already tried many of your suggestions, but the plug wire resistance test I will do tomorrow. Maybe at night so I can see any arching, etc. I'm going to switch some wires #4 (with spark) and say, #2 (no spark) to see if the spark follows it. Thanks!
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Insurance
Please select your insurance company (Optional)

Log-in



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may 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
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 04:28 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.