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gliderman Samba Member
Joined: June 05, 2014 Posts: 19 Location: The Great Midwest
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Posted: Mon Dec 01, 2014 12:49 pm Post subject: '79 FI Cold Start Circuit |
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The cold start circuit on my '79, Calif. Emissions bus is not working. Specifically, the cold start circuit on the double relay has failed twice now due to overheating, leading to melting of the lead trace on the circuit board. I repaired this once by soldering a wire around the damaged area and it worked for awhile, but now it overheated and broke in a different area of the board. Other than hard cold starting, the bus runs fine.
What can cause this to occur? The cold start injector tests out fine, but I haven't been able to test out the thermo-time switch due to its location, but all that does is to ground the circuit to allow the injector to fire.
Ideas anyone?
Tim |
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Tcash Samba Member
Joined: July 20, 2011 Posts: 12844 Location: San Jose, California, USA
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Posted: Mon Dec 01, 2014 1:02 pm Post subject: |
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Windings in the cold start. Did you do a ohms test
Bad crimp connector
Bad connections
Good Luck
Tcash |
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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50349
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Posted: Mon Dec 01, 2014 1:53 pm Post subject: |
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There is a heater circuit in the TTS, the power for which bypasses the cold start valve. If the heater circuit or the wiring for it were grounded out it would cause the problems you are seeing. I am not sure it is possible to swap the plugs between the CSV and the TTS, but if so that could be your problem as well. The plugs are physically the same shape so could be accidentally interchanged if the wiring harness would allow for it. |
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Randy in Maine Samba Member
Joined: August 03, 2003 Posts: 34890 Location: The Beach
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Posted: Mon Dec 01, 2014 2:33 pm Post subject: |
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From the factory the CSV = blue, the TTS = brown, and of course the AAR= black
Last edited by Randy in Maine on Wed Dec 03, 2014 10:34 am; edited 1 time in total |
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Tcash Samba Member
Joined: July 20, 2011 Posts: 12844 Location: San Jose, California, USA
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Posted: Mon Dec 01, 2014 2:46 pm Post subject: |
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Cold start = Blue
TTS = Brown |
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gliderman Samba Member
Joined: June 05, 2014 Posts: 19 Location: The Great Midwest
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Posted: Tue Dec 02, 2014 3:19 pm Post subject: |
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Tcash wrote: |
Windings in the cold start. Did you do a ohms test
Bad crimp connector
Bad connections
Good Luck
Tcash |
Did an Ohm test sorta. Had a spare used cold start; not known to be good. Both the spare and the installed (which I know works when energized) injectors exhibited the same resistance.
Tim |
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Tcash Samba Member
Joined: July 20, 2011 Posts: 12844 Location: San Jose, California, USA
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Posted: Tue Dec 02, 2014 5:29 pm Post subject: |
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As Wildthings posted. Maybe the TTS is shorted?? |
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gliderman Samba Member
Joined: June 05, 2014 Posts: 19 Location: The Great Midwest
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Posted: Wed Dec 03, 2014 10:25 am Post subject: |
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Tcash wrote: |
As Wildthings posted. Maybe the TTS is shorted?? |
I haven't tested the TTS since its not easy to get to. However, would a shorted TTS even make sense as the cause of this problem? I mean after all, its function is to ground the cold start injector circuit for 7-8 seconds until the bi-metallic switch heats up enough to break the ground connection.
I will try to test it. Is there a certain resistance reading that I should look for?
Thanks
Tim |
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Tcash Samba Member
Joined: July 20, 2011 Posts: 12844 Location: San Jose, California, USA
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Posted: Wed Dec 03, 2014 10:32 am Post subject: |
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Wildthings wrote: |
There is a heater circuit in the TTS, the power for which bypasses the cold start valve. If the heater circuit or the wiring for it were grounded out it would cause the problems you are seeing. I am not sure it is possible to swap the plugs between the CSV and the TTS, but if so that could be your problem as well. The plugs are physically the same shape so could be accidentally interchanged if the wiring harness would allow for it. |
The heated circuit could be the problem.
Make sure the wires have not worn threw too. |
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gliderman Samba Member
Joined: June 05, 2014 Posts: 19 Location: The Great Midwest
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Posted: Wed Dec 03, 2014 10:38 am Post subject: |
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Tcash wrote: |
Wildthings wrote: |
There is a heater circuit in the TTS, the power for which bypasses the cold start valve. If the heater circuit or the wiring for it were grounded out it would cause the problems you are seeing. I am not sure it is possible to swap the plugs between the CSV and the TTS, but if so that could be your problem as well. The plugs are physically the same shape so could be accidentally interchanged if the wiring harness would allow for it. |
The heated circuit could be the problem.
Make sure the wires have not worn threw too. |
Will do.
Could perhaps a bad diode in the double relay cause this problem (i.e. too much current through the double relay CS circuit)? I thought about buying a new double relay, but I want to make sure that I'm not going to toast it as soon as I install it |
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Tcash Samba Member
Joined: July 20, 2011 Posts: 12844 Location: San Jose, California, USA
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Posted: Wed Dec 03, 2014 10:48 am Post subject: |
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gliderman wrote: |
Tcash wrote: |
Wildthings wrote: |
There is a heater circuit in the TTS, the power for which bypasses the cold start valve. If the heater circuit or the wiring for it were grounded out it would cause the problems you are seeing. I am not sure it is possible to swap the plugs between the CSV and the TTS, but if so that could be your problem as well. The plugs are physically the same shape so could be accidentally interchanged if the wiring harness would allow for it. |
The heated circuit could be the problem.
Make sure the wires have not worn threw too. |
Will do.
Could perhaps a bad diode in the double relay cause this problem (i.e. too much current through the double relay CS circuit)? I thought about buying a new double relay, but I want to make sure that I'm not going to toast it as soon as I install it |
I don't know. I think the diodes protect the coil and the starter solenoid?
Take a look at this tech tip. Thanks to Amskeptic.
Double Relay Article |
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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50349
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Posted: Wed Dec 03, 2014 11:44 am Post subject: |
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The diode just prevents back feeding of power to the solenoid which would keep the solenoid activated after the points in the AFM close. It also keeps the CSV from getting power after the points close. |
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Amskeptic Samba Member
Joined: October 18, 2002 Posts: 8568 Location: All Across The Country
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Posted: Thu Dec 04, 2014 5:40 pm Post subject: |
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gliderman wrote: |
Could perhaps a bad diode in the double relay cause this problem (i.e. too much current through the double relay CS circuit)? I thought about buying a new double relay, but I want to make sure that I'm not going to toast it as soon as I install it |
Possibly . . . A bad diode would allow the fuel pump run circuit to try to energize the starter solenoid. You would have to look at the path from 88Z to 88A (that is 12 volts battery to the AFM 36/39 switch) and see if the AFM to 86b circuit is continuous to 86. A diode tester would be easiest here. We want 12 volts supplied to 86b to not show up at 86 or 86a.
Colin _________________ www.itinerant-air-cooled.com |
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