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ROW '78 911 Targa
 
timmy2's Avatar
 
Join Date: Jul 2011
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You have carbs, so the brown/black wire from the CIS safety switch is disconnected. (Does nothing)
If you ground the wire (chassis side in the rectangular plastic connector ) it should kill the fuel pump when ignition is on.
The constant 12 volts you have is allowing power to go back to the front fuse panel and keeping things running even with the key off.
Test to see if grounding kills the fuel pump.
Lift CDI red wire to see if switched power becomes normal at the fuses.
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Dennis
Euro 1978 SC Targa, SSI's, Dansk 2/1, Bitz kit EFI.
Need a New Wiring Harness? PM or e-mail me. Search for "harnesses" in the classifieds.
Old 10-11-2017, 03:19 PM
  Pelican Parts Technical Article Directory    Reply With Quote #61 (permalink)
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I'll sneak out to the garage late tonight and figure it out.
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Old 10-11-2017, 04:09 PM
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This is kind of fun but I'm not sure I'm doing the right thing entirely.

Anyway, if I pull the red wire that feeds the MSD , as shown here, then the fuel pump still runs even though the ignition is off. Also, both fuses are always on whether ignition is Switched or not. The number one, bottom fuse, with the MSD wire loses power if I unplug the ignition harness under the dash though.

Ultimately, I am thinking that this means that current to the fuel pump is not back feeding from the MSD, correct?
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Last edited by rbogh901; 10-11-2017 at 08:39 PM..
Old 10-11-2017, 08:33 PM
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Quote:
Originally Posted by timmy2 View Post
If you ground the wire (chassis side in the rectangular plastic connector ) it should kill the fuel pump when ignition is on.

Test to see if grounding kills the fuel pump.
Lift CDI red wire to see if switched power becomes normal at the fuses.


Okay, worth the try, should I disconnect the brown wire at the connector and run a jumper into the chassis side and to the chassis to ground it? I'm not sure that makes intuitive sense but I'm okay with mystery.



When you say lift the red wire does that mean remove it or just lift it?


So far the only way to get one of the fuse terminals always on and the other one off is to disconnect the ignition harness under the dash. Is that what you mean by normal power at the fuses? Seems like that's what I'm looking for.
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Old 10-11-2017, 08:47 PM
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ROW '78 911 Targa
 
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Someone has really screwed up the wiring in your car.
Switched power to the back (a single red wire from front fuse panel) may be hooked up to a constant power fuse instead of a switched power fuse.
If you can determine which bundle of wires is the through body bundle, (one red wire with about 7 or so others of various colors on that branch) you can check to see if it is on fuse 11 or 12 which should be switched power.
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Euro 1978 SC Targa, SSI's, Dansk 2/1, Bitz kit EFI.
Need a New Wiring Harness? PM or e-mail me. Search for "harnesses" in the classifieds.
Old 10-11-2017, 08:56 PM
  Pelican Parts Technical Article Directory    Reply With Quote #65 (permalink)
ROW '78 911 Targa
 
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PM me your phone number if you will be up for a little while.
Or give me a good time to call you tomorrow. We can troubleshoot live then.
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Dennis
Euro 1978 SC Targa, SSI's, Dansk 2/1, Bitz kit EFI.
Need a New Wiring Harness? PM or e-mail me. Search for "harnesses" in the classifieds.

Last edited by timmy2; 10-11-2017 at 09:09 PM.. Reason: Troubleshoot
Old 10-11-2017, 08:59 PM
  Pelican Parts Technical Article Directory    Reply With Quote #66 (permalink)
ROW '78 911 Targa
 
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Alligator clip in plastic connector making good contact, and another one on the fuse panel should work to ground it. (Clips wires together) heck, a paper clip in the connector touching bare metal on the chassis should work too!
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Dennis
Euro 1978 SC Targa, SSI's, Dansk 2/1, Bitz kit EFI.
Need a New Wiring Harness? PM or e-mail me. Search for "harnesses" in the classifieds.
Old 10-11-2017, 09:04 PM
  Pelican Parts Technical Article Directory    Reply With Quote #67 (permalink)
ROW '78 911 Targa
 
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Yes, normal power should be top wire always hot, bottom wire off with ignition.
By unplugging the dash harness you are disconnecting the switched power and any constant power feeds to the front fuse panel where the rear fuse panel is fed from.
Could be the feed to the fuse panel is on an incorrect fuse or the feed to the rear is.
Hope this makes sense. It does to me, but I build these harnesses and know the routing of the wires.
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Euro 1978 SC Targa, SSI's, Dansk 2/1, Bitz kit EFI.
Need a New Wiring Harness? PM or e-mail me. Search for "harnesses" in the classifieds.
Old 10-11-2017, 09:15 PM
  Pelican Parts Technical Article Directory    Reply With Quote #68 (permalink)
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Quote:
Originally Posted by timmy2 View Post
Yes, normal power should be top wire always hot, bottom wire off with ignition.
By unplugging the dash harness you are disconnecting the switched power and any constant power feeds to the front fuse panel where the rear fuse panel is fed from.
Could be the feed to the fuse panel is on an incorrect fuse or the feed to the rear is.


At what point does one suspect a failure in the electrical portion of the ignition switch itself? Apparently they are not unheard of and manifest in many different ways.
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Old 10-12-2017, 05:33 PM
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ROW '78 911 Targa
 
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Quote:
Originally Posted by rbogh901 View Post
At what point does one suspect a failure in the electrical portion of the ignition switch itself? Apparently they are not unheard of and manifest in many different ways.
After confirming the car is wired correctly. And testing it.

Or to test, disconnect the male 6 pin plug and test the switch wiring for correct function of the switch.

Counterclockwise facing male plug using indexing key as pin one.

1. Red/yellow fuse 14
2. Red direct to battery
3. Same as above
4. Not used
5. yellow to start solenoid
6 . Red/Black to fuse 12 switched power and instrument power.

# 6 is a big clue.. if your Gauges work/power up with ignition on, then the ignition switch is working in the on position.

I've been an electrician in the utility industry for almost 30 years.
Troubleshooting control circuits is my specialty. Building new wiring harneses for these cars is my hobby.
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Dennis
Euro 1978 SC Targa, SSI's, Dansk 2/1, Bitz kit EFI.
Need a New Wiring Harness? PM or e-mail me. Search for "harnesses" in the classifieds.

Last edited by timmy2; 10-13-2017 at 10:02 PM..
Old 10-12-2017, 07:48 PM
  Pelican Parts Technical Article Directory    Reply With Quote #70 (permalink)
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Only had a few minutes tonight after everyone went to bed. Tried to ground the brown wire on the chassis side to the chassis and it did not stop fuel pump. No guarantee that I had the perfect connection , gave it the old College try. I tried out my tester light too. Not like I'm a pro but it's kind of fun. Anyway no power between the brown wire and the chassis.
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Old 10-12-2017, 09:09 PM
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Quote:
Originally Posted by timmy2 View Post
After confirming the car is wired correctly.

Or to test, disconnect the male 6 pin plug and test the switch wiring for correct function of the switch.

Counterclockwise facing male plug using indexing key as pin one.

1. Red/yellow fuse 14
2. Red direct to battery
3. Same as above
4. Not used
5. yellow to start solenoid
6 . Red/Black to fuse 12 switched power and instrument power.

# 6 is a big clue.. if your Gauges work/power up with ignition on, then the ignition switch is working in the on position.

I've been an electrician in the utility industry for almost 30 years.
Troubleshooting control circuits is my specialty. Building new wiring harneses for these cars is my hobby.

Cool. This looks like entertainment for sure. Too bad I didn't see it before I went out tonight but I wouldn't have had time anyway. Hopefully over the weekend.
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Old 10-12-2017, 09:11 PM
  Pelican Parts Technical Article Directory    Reply With Quote #72 (permalink)
 
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Looking forward to testing these. I assumed you were talking about the white plug circled in blue here. I only count 5 pins in the picture but maybe mine will be different.


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Last edited by rbogh901; 10-13-2017 at 06:56 AM..
Old 10-12-2017, 09:16 PM
  Pelican Parts Technical Article Directory    Reply With Quote #73 (permalink)
ROW '78 911 Targa
 
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Yes, that is the plug I am referring to.
Important question ...
Do your gauges power up with ignition on and power down with ignition off? (Don't start the car)

Or, does everything turn on (gauges included) when you hook up the battery with ignition off?
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Dennis
Euro 1978 SC Targa, SSI's, Dansk 2/1, Bitz kit EFI.
Need a New Wiring Harness? PM or e-mail me. Search for "harnesses" in the classifieds.

Last edited by timmy2; 10-12-2017 at 10:16 PM..
Old 10-12-2017, 10:11 PM
  Pelican Parts Technical Article Directory    Reply With Quote #74 (permalink)
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Quote:
Originally Posted by timmy2 View Post
Yes, that is the plug I am referring to.
Important question ...
Do your gauges power up with ignition on and power down with ignition off? (Don't start the car)

Or, does everything turn on (gauges included) when you hook up the battery with ignition off?
Jeez Dennis, where do you live? You're up later than I am every night.

Looking forward to testing these outputs/ the ignition switch and leaving a trail for those who might follow. Meantime you are practically reading my mind because it seems like my dash lights are on when they shouldn't B. I have kept the battery unhooked to keep the fuel pump from running, since the thought of it cranking away Non-Stop kind of bugs me. Now, though, I have the fuel relay pulled out and can leave the battery connected while I check things. I'll get back.


Pm coming.
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Old 10-13-2017, 11:07 AM
  Pelican Parts Technical Article Directory    Reply With Quote #75 (permalink)
ROW '78 911 Targa
 
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I'm in Oregon, so it is earlier for me than it is for you in Utah.
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Dennis
Euro 1978 SC Targa, SSI's, Dansk 2/1, Bitz kit EFI.
Need a New Wiring Harness? PM or e-mail me. Search for "harnesses" in the classifieds.
Old 10-13-2017, 11:12 AM
  Pelican Parts Technical Article Directory    Reply With Quote #76 (permalink)
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