Purple-Yellow Starter Wires - Team Camaro Tech
Electrical & Wiring Troubleshooting electrical.

 
LinkBack Thread Tools Display Modes
post #1 of 9 (permalink) Old May 29th, 09, 10:44 AM Thread Starter
Senior Tech
Alan
 
Join Date: Oct 2007
Location: SoCal
Posts: 3,905
Purple-Yellow Starter Wires

Can someone verify for me: The purple wire to the starter solenoid delivers 12V to the solenoid causing it to engage. 12V is also passed to the yellow wire which goes from the solenoid to the coil giving 12V during engine crank? The yellow and purple then go to 0V when the key start is released to run position?

I have been having hot solenoid jitters at crank. I felt the purple-yellow wire bundle behind the exhaust manifold log and it feels like the insulation is hardened and cracking. No doubt the copper is pretty beat up at that point which could be causing my solenoid to jitter when hot cranking?

Is my best bet to replace the purple wire at the firewall junction block or just solder in a new lead where the purple wire comes across the top of the firewall in the rubber channel? According to the wiring diagram, the yellow merely goes from the inner terminal on the solenoid to the coil.

thanks guys

alan
alanrw is offline  
Sponsored Links
Advertisement
 
post #2 of 9 (permalink) Old May 29th, 09, 11:28 AM
Super Moderator
Bess-68's rule
 
Everett#2390's Avatar
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 31,876
Garage
Re: Purple-Yellow Starter Wires

You could solder in a section of new wire at the firewall channel. The new wire should have EE or EEE insulation, meaning Teflon® insulated to avoid the effects of the heat.

Later engines, '80's?, have a heat tube with the wire harness passing through and attached to a bellhousing bolt preventing this condition.

If this didn't work, then replace the whole wire from the connector to solenoid.

Give a man a rescued dog for the health of both their souls. May 2017 ROTM Winner - Thank you!
'
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
CUBS - 2016 World Series Champions - Thank you, Joe Madden enjoy your next chapter.
Everett#2390 is offline  
post #3 of 9 (permalink) Old May 29th, 09, 11:29 AM
Senior Tech
 
Join Date: Mar 2002
Location: Austin, TX, USA
Posts: 5,277
Re: Purple-Yellow Starter Wires

You are correct about the connection of the purple and yellow wires. The yellow wire provides 12V to breaker point ignitions (bypassing the resistor wire) for an additional spark boost during crank. Non breaker point ignitions (HEI and other electronic) don't need the yellow wire - with the exception of some 1967 vehicles which did not keep the IGN feed hot during crank.

It sounds like you may be describing a "heat soak" problem. The theory is that header heat causes the solendoid to build up high internal resistance preventing it from working properly.

I am a big fan of the "voltage drop" method of finding electrical problems. For example, during crank, the voltage on the battery (+) terminal should be nearly the same as the voltage on the purple wire at the solenoid. And, if the voltage is exactly the same, a voltage reading between those two points (while attempting to crank) should be zero. In reality, you're always going to see a little voltage between those two points, but it should be very small (less than 0.1V). [Actually, the voltage you see between points will vary depending on the load]. If you find the voltage drop is much higher, begin moving your measurement points around the circuit under test until you isolate the component or components where the voltage drop resides.

Starter heat soak theory would indicate that very little voltage drop exists between the battery (+) and purple wire at the starter. Instead the resistance would live within the solenoid coil or between the solenoid's power wire and the motor (accross the contactor terminals internal to the solenoid). To my knowledge no one here has posted any results of such a test and usually jump straight on to heat sheilds or external contactor/relay setups. However it may actually be that the ignition switch itself or the firewall bulkhead connector is heating up while the car is running causing the resistance of a bad connection to increase. The external solenoid / relay work around would eleviate the symptoms but not necessarily remove the root cause. As a result, I personally would use the voltage drop method to make certain the crank issue is in fact a starter heat soak related problem before I spent too much time replacing parts or modifying the crank circuit. It should be a pretty quick and easy thing to check when the starter is acting up. Just realize the voltage drop readings only have meaning when you activate the circuit under test (cranking in this case). The only issue would be avoiding a burn while you try to test the circuit on a hot motor.

Dave
========================
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
dnult is offline  
 
post #4 of 9 (permalink) Old May 29th, 09, 11:43 AM Thread Starter
Senior Tech
Alan
 
Join Date: Oct 2007
Location: SoCal
Posts: 3,905
Re: Purple-Yellow Starter Wires

Dave, I am assuming that you put the black lead of the DVM on ground and then the red lead goes to the test points you mentioned in your post. But if you put one lead on the battery + and the other on the purple lead you are saying you can get a voltage reading?

And if it were indeed the ignition switch or bulkhead connection, then I would expect a drop at the purple wire on the solenoid compared to the battery terminals, correct?

A friend had the same problem with his truck. He took it to a shop that specializes in starter alternator issues. The issue turned out to be the spring in the solenoid growing as it got hot. Replacing the spring with one that was 1/8" shorter solved the problem.

But let's check out the simple obvious issues before we get complex-when you hear hoof beats, think horses not zebras.

alan
alanrw is offline  
post #5 of 9 (permalink) Old May 29th, 09, 03:55 PM
Senior Tech
 
Join Date: Aug 2004
Location: PA
Posts: 819
Re: Purple-Yellow Starter Wires

Quote:
Originally Posted by alanrw View Post
According to the wiring diagram, the yellow merely goes from the inner terminal on the solenoid to the coil.
thanks guys
alan
The purple wire goes on the small terminal closest to the engine. The yellow wire goes on the small terminal farthest from the engine.

69 RS 355 Tremec 5-Speed 4.11's
12run is offline  
post #6 of 9 (permalink) Old May 29th, 09, 04:06 PM Thread Starter
Senior Tech
Alan
 
Join Date: Oct 2007
Location: SoCal
Posts: 3,905
Re: Purple-Yellow Starter Wires

If the purple is on the outboard, it is a no start, correct?

alan
alanrw is offline  
post #7 of 9 (permalink) Old May 29th, 09, 04:14 PM
Super Moderator
Bess-68's rule
 
Everett#2390's Avatar
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 31,876
Garage
Re: Purple-Yellow Starter Wires

Purple to 'S', yellow to 'R'

Give a man a rescued dog for the health of both their souls. May 2017 ROTM Winner - Thank you!
'
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
CUBS - 2016 World Series Champions - Thank you, Joe Madden enjoy your next chapter.
Everett#2390 is offline  
post #8 of 9 (permalink) Old May 29th, 09, 04:22 PM Thread Starter
Senior Tech
Alan
 
Join Date: Oct 2007
Location: SoCal
Posts: 3,905
Re: Purple-Yellow Starter Wires

And those letters are stamped on the nose of the solenoid (connecter end)?

alan
alanrw is offline  
post #9 of 9 (permalink) Old May 29th, 09, 04:23 PM
Senior Tech
 
Join Date: Aug 2004
Location: PA
Posts: 819
Re: Purple-Yellow Starter Wires

Quote:
Originally Posted by alanrw View Post
If the purple is on the outboard, it is a no start, correct?
alan
In theory that is correct, but it's worth checking. Some solenoids only have one small terminal (newer HEI model) and if you have the yellow and purple wires on the same terminal it will cause problems.

69 RS 355 Tremec 5-Speed 4.11's
12run is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user 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.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



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

 
For the best viewing experience please update your browser to Google Chrome