Help!! - 3.7 volts at coil pos.(no hair left..) - Hot Rod Forum : Hotrodders Bulletin Board -- Hot Rod Forum

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

LinkBack Thread Tools
  #1 (permalink)  
Old 09-07-2006, 03:09 PM
dabongo's Avatar
A 'GO!' addict..
Join Date: Mar 2006
Location: The Couv, Wa
Age: 51
Posts: 14
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Help!! - 3.7 volts at coil pos.(no hair left..)

My PITA continues..
I'm working on a 78 Dodge Class C Motor home with a 440/4bl motor.
I need to go camping before I lose my mind - or so I can find it....

Refering to my previous post; 440-dodge-weak-no-spark-wont-start

The motor was cranking, but showed little to no spark. At that time I was seeing 5.7. It turned out the problem was being caused by a bad distributor(and I mean bad).. I installed a new distributor and the engine appeared to fire up(I only let it catch a little because the wiring harness, etc. needed to be put back in place. I didn't need the fan catching a harness wire...)

When I looked at the distributor again it appears one of us moved it when putting the wires, cap, etc back in place. It was advanced about a quarter obviously the ignition was running at huge adv. Well, when I moved it back to TDC and tried to start it again, no go...just some light popping(not back fire.. just the sound of compression being pushed out a 'just opened' valve.) I decided to move the dist. back to the Adv. position again and turn it over.
It acted like it wanted to start, but doesn't actually fire...back to TDC I put it..

I went back to start doing some troubleshooting again and found that when I have the key in 'run' position(not 'start') I'm seeing 3.7 volts at the coil positive, and 1.7 at coil negative(with the ECU plugged in, and the battery shows 12.5v).
When the ignition is in 'start'(engine cranking strong) I'm seeing 10.7 volts at Coil positive(which I assume is correct since the starter relay boosts voltage during the start cycle)...

So I need some advice on my Low Voltage at Coil Positive.

Before the whole problem started I was seeing around 6v at coil positive, under the same conditions.

Doc - thanks for all your advice last time. But I guess I'm not done yet...

Just to mention;
1) I'm being told I should see no less than 6v(+/-) at coil positive to get a strong enough spark to run on...

2) After I 'thought' I had the thing running I added a MSD blaster 2 coil. I just received the replacement ECU harness from Summit and will be installing it tonight...

Thanks for looking..

Reply With Quote Quick reply to this message
Sponsored Links
  #2 (permalink)  
Old 09-07-2006, 04:47 PM
docvette's Avatar
Registered User
Last wiki edit: Rebuild an alternator Last photo:
Join Date: Mar 2004
Location: Lafayette, california
Age: 64
Posts: 7,360
Wiki Edits: 12

Thanks: 0
Thanked 7 Times in 4 Posts
Doc here,

Jump from the battery to the coil + and see if it will fire and run.

If it does, then the problem can only exist between the ballast resistor and the Ignition switch..

If it does not..your new Dizzy may be faulty (or not grounded)

Reply With Quote Quick reply to this message

Recent Electrical posts with photos

Quick Reply

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:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Please select your insurance company (Optional)


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

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

Similar Threads
Thread Thread Starter Forum Replies Last Post
Ignition system info................ poncho62 Electrical 18 10-11-2008 10:10 PM
How Does This Stuff Work? docvette Electrical 3 06-18-2006 03:00 AM
Power Seats MI2600 Electrical 4 10-06-2005 04:55 AM
A question on coils denbar Electrical 1 03-17-2005 02:22 PM
Push botton starter street rodder 1937 Electrical 4 03-17-2005 09:19 AM

All times are GMT -6. The time now is 08:42 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, 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 © 2017 DragonByte Technologies Ltd.
Copyright 1999 - 2012. All Rights Reserved.