Tach wire shutting down my engine - Team Camaro Tech
Team Camaro Tech join team camaro
 
Camaro Parts at SS396.com     
GROUND UP & SS396.com         
Official Sponsor of Team Camaro
   

Auto Insurance



Registered users (free) do not see these large ads

Electrical & Wiring Troubleshooting electrical.

Reply
 
Thread Tools Display Modes
  #1  
Old Apr 24th, 12, 07:50 PM
BUFFDRIVER BUFFDRIVER is offline
Tech Team

CHOPS
 
Join Date: Dec 2011
Location: La
Posts: 58
Default Tach wire shutting down my engine

I can't make this crap up. So after my 4 month ordeal with my 6 speed trans I finally get it out for a cruise with my daughter and I broke down. The distributor cap broke (torque made it hit the firewall) and tore the rotor all to hell. Fine, I throw another one on and make my way home and it starts to run like crap. I pull over, mess with the cap, get it to start again and make it home. I go to start it and nothing. Long story short after replacing the cap, rotor, coil, module, and a whole new distributor I got nothing. Finally trouble shoot it to the factory tach wire going to the cap. Ohmed it out and it reads 0.3. Is this normal? If I hook it up the car won't start. Why will the tach wire shut the car off if it's grounded? Did I fry my tach? How do I test it? I did install a DIY tach filter and everything did work for over 100 miles. This car is going to give me an ulser.
Reply With Quote
Sponsored Links
Advertisement
 
  #2  
Old Apr 25th, 12, 03:42 AM
Everett#2390's Avatar
Everett#2390 Everett#2390 is offline
Moderator

<Jake 68's Rule
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 27,261
Default Re: Tach wire shutting down my engine

I would suspect the filter 'bit the dirt'. The filter blocks the DC voltage but passes the AC component, the tach pulses, to the tach input coil and you are reading the primary winding of the coil circuit.
Time for an aftermarket tach.........
__________________
Give a man a rescued dog for the health of his soul.
'With enough thrust, pigs can fly.' Other Stuff
Reply With Quote
  #3  
Old Apr 25th, 12, 01:06 PM
Eric Kammerer Eric Kammerer is offline
Senior Tech

 
Join Date: May 2004
Location: Southeast PA
Posts: 8,302
Default Re: Tach wire shutting down my engine

Yup. When I was trying to troubleshoot if my OE tach was completely dead or just needed a signal filter, I made an adjustable one as described in the thread, to make sure I made one with the right components. When I turned the knob trying to find the setting needed to make the tach move, I found I could shut off the engine with the knob. So I gave up on the filter idea and set the tach out for rebuild (which it needed anyway, because it was completely dead). But I had never experienced such a small circuit killing the whole ignition like that.
__________________
Eric
69 'vert project big block/TKO 600 RR
68 'vert driver RS clone -- gone!
Reply With Quote
  #4  
Old Apr 25th, 12, 04:39 PM
BUFFDRIVER BUFFDRIVER is offline
Tech Team

CHOPS
 
Join Date: Dec 2011
Location: La
Posts: 58
Default Re: Tach wire shutting down my engine

I'm wondering if when the rotor let go the metal could have shorted something out under the cap.
Reply With Quote
  #5  
Old Apr 26th, 12, 09:03 AM
BUFFDRIVER BUFFDRIVER is offline
Tech Team

CHOPS
 
Join Date: Dec 2011
Location: La
Posts: 58
Default Re: Tach wire shutting down my engine

GOOD NEWS! It was the filter. The tach works fine without it.
Reply With Quote
  #6  
Old Apr 26th, 12, 07:13 PM
go2fast go2fast is offline
Senior Tech

Jim
 
Join Date: Jul 2005
Location: MA
Posts: 1,915
Default Re: Tach wire shutting down my engine

We used to use the tach line for kill switches at the Chevy dealer I worked at many years ago.
Reply With Quote
  #7  
Old Apr 26th, 12, 09:15 PM
Steptoe Steptoe is offline
Senior Tech

Steps
 
Join Date: Dec 2005
Location: New Zealand
Posts: 12,870
Default Re: Tach wire shutting down my engine

Quote:
We used to use the tach line for kill switches at the Chevy dealer I worked at many years ago.
That is a bit of useful information....
Thoughts on that Everett any issues that could arise?
Reply With Quote
  #8  
Old Apr 26th, 12, 09:41 PM
Steiner Steiner is offline
Senior Tech

Steiner
 
Join Date: Mar 2009
Location: Lyman, SC
Posts: 7,696
Default Re: Tach wire shutting down my engine

Probably isn't an issue unless ignition power is left on for awhile with the kill switch engaged. Otherwise it's like leaving the key on in a points system with the points closed although the points will about always give it up first.
__________________
'69 Camaro X11 Street Car
Dart 400 - AFR-195's - 224/224 HR - Powerjection III
TKO-600 - Moser 3.42 - Detroit Truetrac
538 lb-ft - 500 hp
www.cmengines.com
'69 Camaro X44 Beater - SFT 327 - M20 - Moser 4.10
'02 Z/28 vert - stock
Reply With Quote
  #9  
Old Apr 27th, 12, 03:26 AM
Everett#2390's Avatar
Everett#2390 Everett#2390 is offline
Moderator

<Jake 68's Rule
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 27,261
Default Re: Tach wire shutting down my engine

As Steiner suggested, not an issue, if used momentarily.
If ign switch left on and wire still grounded, contacts on point set will 'weld' themselves together.
__________________
Give a man a rescued dog for the health of his soul.
'With enough thrust, pigs can fly.' Other Stuff
Reply With Quote
  #10  
Old Apr 27th, 12, 07:08 PM
Steptoe Steptoe is offline
Senior Tech

Steps
 
Join Date: Dec 2005
Location: New Zealand
Posts: 12,870
Default Re: Tach wire shutting down my engine

With GM HEI not sure if u guys know this but leave the key on and the module switches off by itself...u cant burn out the coil etc.
And from above...dont understand this
Quote:
The distributor cap broke (torque made it hit the firewall) and tore the rotor all to hell.
How can a dizzy hit the firewall when engine movement is lateral???
Even ripping apart a engine mount and having a wide cap GM HEI it cant hit the firewall.
Reply With Quote
  #11  
Old Apr 27th, 12, 07:41 PM
Steiner Steiner is offline
Senior Tech

Steiner
 
Join Date: Mar 2009
Location: Lyman, SC
Posts: 7,696
Default Re: Tach wire shutting down my engine

Yes, that's what a I was referring to and just comparing it to leaving points system turned on. Kill switch should only be an issue on a points system with key left on since it would power the coil to ground. No issue with the points themselves unless they were also closed and still probably not an issue as the kill switch would be parallel with the points and most likely be best path to ground.

With an HEI you'd still have the issue of coil heating up after awhile if using a simple kill switch because you'd still be powering the coil with a ground connected to the negative terminal which is not the same state as when just the key is turned on.

Bottom line is that it's not good for any dc coil to be left with power on the positive and straight ground on the negative for a long time. I reckon you could add an rc circuit or just a resistor to it to protect the coil like the condensor but for a simple kill switch there's no reason to since who leaves their key on and then just walks away from the car? OK, me when I used to listen to the radio in my dad's truck but that's about it.
__________________
'69 Camaro X11 Street Car
Dart 400 - AFR-195's - 224/224 HR - Powerjection III
TKO-600 - Moser 3.42 - Detroit Truetrac
538 lb-ft - 500 hp
www.cmengines.com
'69 Camaro X44 Beater - SFT 327 - M20 - Moser 4.10
'02 Z/28 vert - stock
Reply With Quote
  #12  
Old Apr 27th, 12, 07:50 PM
go2fast go2fast is offline
Senior Tech

Jim
 
Join Date: Jul 2005
Location: MA
Posts: 1,915
Default Re: Tach wire shutting down my engine

Quote:
Originally Posted by Everett#2390 View Post
As Steiner suggested, not an issue, if used momentarily.
If ign switch left on and wire still grounded, contacts on point set will 'weld' themselves together.

I'm sorry, but this makes no sense. The points ground the coil. So putting a switch on the negative of the coil (to ground) bypasses the points entirely. The coil and resistor wire will draw a little current, but that's about it. Besides, I thought we were talking about an HEI?
Reply With Quote
  #13  
Old Apr 27th, 12, 08:00 PM
Steiner Steiner is offline
Senior Tech

Steiner
 
Join Date: Mar 2009
Location: Lyman, SC
Posts: 7,696
Default Re: Tach wire shutting down my engine

Quote:
Originally Posted by go2fast View Post
I'm sorry, but this makes no sense. The points ground the coil. So putting a switch on the negative of the coil (to ground) bypasses the points entirely. The coil and resistor wire will draw a little current, but that's about it. Besides, I thought we were talking about an HEI?

You're right. See above. I just mentioned the points as a comparison to what it's like just grounding the igition system...as in you can damage something if left for awhile. I think Everett was just making a quick response that came out wrong.
__________________
'69 Camaro X11 Street Car
Dart 400 - AFR-195's - 224/224 HR - Powerjection III
TKO-600 - Moser 3.42 - Detroit Truetrac
538 lb-ft - 500 hp
www.cmengines.com
'69 Camaro X44 Beater - SFT 327 - M20 - Moser 4.10
'02 Z/28 vert - stock
Reply With Quote
  #14  
Old Apr 28th, 12, 06:55 AM
Everett#2390's Avatar
Everett#2390 Everett#2390 is offline
Moderator

<Jake 68's Rule
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 27,261
Default Re: Tach wire shutting down my engine

Steiner's right, I reread this AM, and it doesn't read correctly.
I honestly don't know what I was thinking................
__________________
Give a man a rescued dog for the health of his soul.
'With enough thrust, pigs can fly.' Other Stuff
Reply With Quote
Sponsored Links
Advertisement
 
Reply

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 -7. The time now is 08:52 AM.



Camaros.net - 2009 AutoForums.com