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Author Topic: Help trouble shooting a cowl induction system  (Read 2508 times)
Flowjoe
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« on: January 05, 2006, 08:28:00 PM »

I am helping a friend in the final stages of finishing up his 69 Z.  I have never set up a cowl induction system before so am flying a little blind not know exactely what should be hot and when.  Here is what I have done so far:

1) I've tested the throttle switch off the car for resistance (on JohnZ's advice, thanks John) .  It had a near zero reading when not depresed and a very high reading when depressed so I installed it in the car.  

2) I have checked power power at the relay...I get a constant 12V at the tan wire.  The Pink wire varies with the position of the throttle switch  (I have manually depressed the plunger to be certain that it is fully depressed).  Should the pink be hot at 12V when the switch is open or depressed?

3) I seem to be getting a constant 12V, via the black wire from the relay, to the solenoid.  should his be?  Or should it only be hot  when the throttle switch is depressed?  

4) I tried to bypass the relay by jumping across the pink & black wires but I had no change.

Since I am getting inconsistant results from the throttle switch I suspect  that I have a bad  switch.  but since I don't know whehter the switch should send current or cut off currrent  I can't tell whether I have other problems.  My assumption is that the solemoind should not receive 12V until the switch is depressed   I suspect  that the repay may also be faulty .  And since the solenoid does not operate when 12V is applied I am also assuming it is faulty.  

Can someone lend me some input and expertise so that I don't go and buy a bunch of new components that I may not need?

thanks in advacne.

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PACE&Z2869
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« Reply #1 on: January 06, 2006, 02:00:12 AM »

TAKE A CLOSE LOOK AT THE SOLENOID. I KNOW THAT THE REPRODUCTION SOLENOIDS THE TINY WIRE THAT COMES OUT OF THE SOLENOID TO THE SPADE CONNECTOR CAN MAKE CONTACT W/ THE METAL HOUSING AND BURN THE TINY WIRE IN HALF. AFTER REPAIRING MY SOLENOID I USED SOME SILICONE TO PREVENT THIS TINY WIRE FROM CONTACTING THE HOUSING AGAIN. THE SWITCH ON THE LINKAGE IF IT IS REPRODUCTION ARE ALSO LESS THAN PERFECT. I USED SOME .032 AIRCRAFT  SAFETY WIRE AROUND THE PLASTIC BODY IN A GROOVE TO HELP HOLD THE SWITCH TOGETHER PROPERLY. AFTER DOING THIS THE SWITCH WAS CONSISTANT APON TESTING W/ A VOLTMETER FOR CONTINUITY. THE SWITCH SHOULD MAKE CONNECTION WHEN PRESSED.
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PACE&Z2869
Flowjoe
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« Reply #2 on: January 06, 2006, 09:36:25 AM »

Thanks Pace&Z2869 for responding. 

so I have the concept right then?  When depressed the switch should send 12V to the relay via the pink wire, then the relay should  send 12V to the solenoid via the black wire, and then the solenoid should activate. Huh  If this is corrrect I have to ask, why the relay?

I believe the switch to be original but I am uncertain about the solenoid, I'll check the connection you outline. 

any other thoughts?  anyone?
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JohnZ
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« Reply #3 on: January 06, 2006, 01:00:27 PM »

A pink wire from the "Ign" cavity in the fuse block goes to one side of the switch, and a pink wire from the other side of the switch goes to the coil in the relay; the relay coil grounds through the case tab, where it's screwed to the firewall. When the switch is closed at WOT, that sends 12V to the relay coil, which closes the points in the relay. One side of the points has a tan wire to the fuse block (power), and the other side of the points has a tan wire that goes up to the solenoid in the hood, which is grounded through its attachment to the hood. When the relay points close at WOT, that sends 12V through the tan wire to the solenoid, which energizes it and opens the air valve. If you don't have a good clean ground where the solenoid is attached to the hood, it won't work. The reproduction throttle arm switch is junk - the GM switch works fine.
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'69 Z/28
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Flowjoe
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« Reply #4 on: January 06, 2006, 07:12:47 PM »

A pink wire from the "Ign" cavity in the fuse block goes to one side of the switch, and a pink wire from the other side of the switch goes to the coil in the relay; the relay coil grounds through the case tab, where it's screwed to the firewall. When the switch is closed at WOT, that sends 12V to the relay coil, which closes the points in the relay. One side of the points has a tan wire to the fuse block (power), and the other side of the points has a tan wire that goes up to the solenoid in the hood, which is grounded through its attachment to the hood. When the relay points close at WOT, that sends 12V through the tan wire to the solenoid, which energizes it and opens the air valve. If you don't have a good clean ground where the solenoid is attached to the hood, it won't work. The reproduction throttle arm switch is junk - the GM switch works fine.

OK John, I am with you up to a point.  I have a pink wire running from the fuse block IGN to the switch and then from the switch to the relay.  I have a tan wire running from the fuse block ACC directly to the relay.  the relay has a three prongs.  the tan wire stands alone on the passenger side of the relay.  the pink wire is in a  two prong "T" shaped fitting and plugs into the driver's side prong while a black wire connects to the center prong (using the same "T" shaped plug) and leads to the solenoid. 
When the key is the run position the tan wire is always hot.  Mostly the black wire to the solenoid is hot (12V) but occiasionally the switch seems to interrupt the current (the occaisionally part is the bit that makes me think the switch is bad).  Does this configuration sound correct to you? 

I don't own any cars with cowl induction so have never had to mess with it.  This car was not originally equipped with the the cowl hood (as the firewall was not drilled for the wiring harness - instead it was fed through the clutch rod hole) but someone seems to have collected all of the parts (I don't know if the are correct or good parts) such as the flapper door, seal, throttle arm with fitting for the switch etc. 

From your discription it sounds as if I should not have three wires at the relay and that I should not have two sources of power there.  Any further light you can shed on this would be reatly appreciated.


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JohnZ
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« Reply #5 on: January 07, 2006, 12:37:03 PM »

Yes, there are two power sources - one for the switch to the relay coil (pink wire from the "Ign" cavity), and one to the points for the solenoid (tan wire from the "Acc" cavity).

Photo below of the relay and its connections - the "T" connector has two wires; the inboard pink wire is power from the fuse block through the throttle arm switch to the relay coil, the tan wire next to it is power out to the solenoid from the points in the relay, and the single connector on the outboard side of the relay is power-in to the points from the fuse block. There are no black wires in the original configuration - the wire from the relay to the solenoid is tan.
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'69 Z/28
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