Clutch starter interlock question
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Heel & Toe
Joined: Oct 2011
Posts: 21
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Clutch starter interlock question
I have a 74 4-speed that will start with clutch up or down. Obviously some previous owner bypassed this switch. Is there supposed to be a lockout if the trans in not in neutral also? Because it also starts any gear, with clutch down, for my own safety!
So is there a shifter lockout and a clutch lockout for starting, or just clutch/ Thanks
So is there a shifter lockout and a clutch lockout for starting, or just clutch/ Thanks
Melting Slicks
Joined: Mar 2005
Posts: 2,093
Likes: 297
From: Midlothian VA
I have a 74 4-speed that will start with clutch up or down. Obviously some previous owner bypassed this switch. Is there supposed to be a lockout if the trans in not in neutral also? Because it also starts any gear, with clutch down, for my own safety!
So is there a shifter lockout and a clutch lockout for starting, or just clutch/ Thanks
So is there a shifter lockout and a clutch lockout for starting, or just clutch/ Thanks
Le Mans Master
Joined: Aug 2006
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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Instructor
Joined: Aug 2013
Posts: 234
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From: Johnston Rhode Island
There is such a thing as an interlock (typically a rocker switch) that can be pressed/held and you can start a manual without touching the clutch. Nissan actually made some of their king can pick ups back in the 80's with these switches standard.
I have never seen them in a corvette and they really don't serve any useful purpose. I would be curious how this is being accomplished without having to throw a switch.
I have never seen them in a corvette and they really don't serve any useful purpose. I would be curious how this is being accomplished without having to throw a switch.
Le Mans Master
Joined: Aug 2006
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Trick question on a 74 Stingray!
For most Corvettes 12 volts positive is at the key switch but with the key "OFF" the switch is open and the power stops there.
When you turn the switch to "START" 12 volts goes to the clutch switch and cannot go and further until you step on the clutch.
After you step on the clutch the power goes to the starter.
On 1974 and some early 1975's there is a "Seat Belt / Starter Interlock".
The idea was that each passenger had to buckle up before the car would start.
It's a complicated system and many owners have bypassed that relay. There are several pages about that system in the 74 service manual starting on p 12-62.
Lets keep it simple, do you have to buckle up before your car normally would start?
Le Mans Master
Joined: Oct 2006
Posts: 6,842
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From: Palmdale CA
And that switch for the clutch... It is deep inside and nearly at the top of the dash. It is almost impossible to access from underneath. I recently adjusted mine, when the dash was out, because I used to have the mash the pedal into the carpet to get it to start, but now, I just have to get close. It just comes up short of touching the carpet by a 1/4" to 1/2".
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Thread Starter
Heel & Toe
Joined: Oct 2011
Posts: 21
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clutch neutral switch
Thanks for the great diagrams, the previous owner diabled a lot of things, the car will start without the seatbelts buckled, and without the clutch being down. It starts in neutral with the clutch engaged, (UP). Have never had a problem, until last night, would not turn the starter when key was turned to 'start'.
A friend was able to 'jump' the starter solenoid, and it started right up.
When I got it home, it of course started right up, several times, like nothing had happened. Guess I need to trace out the 'modifications' and find a loose connection. It was parked on an uphill, which makes me think it is a wire or some connection just moving enough to cause it to disengage, where on the level it it fine. Previous owner.....
A friend was able to 'jump' the starter solenoid, and it started right up.
When I got it home, it of course started right up, several times, like nothing had happened. Guess I need to trace out the 'modifications' and find a loose connection. It was parked on an uphill, which makes me think it is a wire or some connection just moving enough to cause it to disengage, where on the level it it fine. Previous owner.....
Le Mans Master
Joined: Aug 2006
Posts: 7,417
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Thanks for the great diagrams, the previous owner diabled a lot of things, the car will start without the seatbelts buckled, and without the clutch being down. It starts in neutral with the clutch engaged, (UP). Have never had a problem, until last night, would not turn the starter when key was turned to 'start'.
A friend was able to 'jump' the starter solenoid, and it started right up.
When I got it home, it of course started right up, several times, like nothing had happened. Guess I need to trace out the 'modifications' and find a loose connection. It was parked on an uphill, which makes me think it is a wire or some connection just moving enough to cause it to disengage, where on the level it it fine. Previous owner.....
A friend was able to 'jump' the starter solenoid, and it started right up.
When I got it home, it of course started right up, several times, like nothing had happened. Guess I need to trace out the 'modifications' and find a loose connection. It was parked on an uphill, which makes me think it is a wire or some connection just moving enough to cause it to disengage, where on the level it it fine. Previous owner.....
So you don't short anything out:
Remove and clean the negative battery cable on the battery and on the other end which is under the car below the drivers seat. Leave that cable disconnected and clean the positive at the battery and the other end at the big terminal on the starter solenoid.
REconnect the negative and try to start your car.
Good that your car starts without having to buckle up as that's another can of worms!
There is another negative cable from the starter to the block at the motor mount.
Melting Slicks
Joined: Mar 2005
Posts: 2,093
Likes: 297
From: Midlothian VA
Melting Slicks
Joined: Jul 2009
Posts: 2,091
Likes: 40
That clutch interlock switch is in an awful place to get to.....whew...I mean you need to be able to bend like a 16 year old cheerleader to reach it.
I don't blame someone for bypassing it .....it's a 60 sec, job to bypass it and damn near impossible to get too......at my advanced age.
Seems to me it was a pair of big purple wires .....so look for a wire nut , tape etc...and purple wires under the driver side above fuse box,....I think I remember ...it was pain the BACK to reach.
I don't blame someone for bypassing it .....it's a 60 sec, job to bypass it and damn near impossible to get too......at my advanced age.
Seems to me it was a pair of big purple wires .....so look for a wire nut , tape etc...and purple wires under the driver side above fuse box,....I think I remember ...it was pain the BACK to reach.
Last edited by LS4 PILOT; May 27, 2014 at 08:09 PM.
Thread Starter
Heel & Toe
Joined: Oct 2011
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Hi, battery is not the problem, it is 1 year old this month. Car has started maybe 10 times perfectly since that one time. Going to park it on a hill again and see if I can get it to fail again. I did notice when I was trying that one time that it did not start, the "brake" light in the speedo would dim just like it does when you hit the starter, so I know juice was getting somewhere, just not to the solenoid. Got a bit of hunting around to do I guess. usually a black tape job coming loose, that is why I think it had something to do with the car being tilted. All my friend did was jump the hot battery lead on the starter to the ignition wire on the solenoid and it started fine, all I was missing was the current to the solenoid. thanks for all the suggestions.
Le Mans Master
Joined: Aug 2006
Posts: 7,417
Likes: 1,554
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Hi, battery is not the problem, it is 1 year old this month. Car has started maybe 10 times perfectly since that one time. Going to park it on a hill again and see if I can get it to fail again. I did notice when I was trying that one time that it did not start, the "brake" light in the speedo would dim just like it does when you hit the starter, so I know juice was getting somewhere, just not to the solenoid. Got a bit of hunting around to do I guess. usually a black tape job coming loose, that is why I think it had something to do with the car being tilted. All my friend did was jump the hot battery lead on the starter to the ignition wire on the solenoid and it started fine, all I was missing was the current to the solenoid. thanks for all the suggestions.
Le Mans Master
Joined: Aug 2006
Posts: 7,417
Likes: 1,554
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
The jumper on the bottom of his page 1 is easy to do and you will not ruin a rare and hard to find relay.
Instructor
Joined: Mar 2014
Posts: 170
Likes: 2
From: Alice Texas
Could it be the starter solenoid. Maybe the piston that engages the bendix was stuck and the "extra" boost from the jump freed it up. You said you thought the power was going somewhere.
One thing for sure, it will end up leaving you at the most in convenient time. Hope you find the cause first.
One thing for sure, it will end up leaving you at the most in convenient time. Hope you find the cause first.