63 Ground strap education

[Steve D.]

I am chasing a starting circuit problem. I know there are a number of grounding straps, but I thought most were associated with mitigating radio interference. Is it necessary to ground the engine block to the frame, and if so, how is it properly done.

Steve

[William C.]

Re: 63 Ground strap education

Ground to the starting circuit is accomplished via the negative battery cable connection at the starter mounting bolt. What are the symptoms of your problem?

[Steve D.]

Re: 63 Ground strap education

Bill

I am attempting to start the engine with the body off using the main harness and ignition harness. Everything is hooked up including alternator, regulator, horn relay, ballast resistor. The neg battery cable is attached to a starter bolt. A black with white stripe wire is attached to the radiator mount with on of the regulator screws, and the instrument cluster ground (black with white stripe) is grounded to the frame. I have the ignition switch connected in the main harness. When I turn to start, I get nothing.

Steve

[mike cobine]

Re: 63 Ground strap education

I can't find my wiring diagram anywhere, but I'd bet that you need those grounds because your horn relay and voltage regulator are mounted to the core support. It grounds to the frame, but the engine doesn't without the ground straps. Now the voltage regulator is isolated by rubber grommets (or should be) and gets its ground connect via the grounding wire.

For your test, I'd grab a pair of jumper cables and connect the engine to the frame and try again.

Simple test, use a test light to check:
-- voltage at battery (+ to -)
-- voltage at starter battery bolt (starter bolt to engine)
-- voltage at solenoid when key in start (inner solenoid screw to engine)

If those three light, then you have two choices - bad starter or bad battery. Connect the test light across the battery, hit the key to start, and see if the light goes out. If so, toss the battery if you can't charge it.

[William C.]

Re: 63 Ground strap education

Using a voltmeter, I would check from the 12feed at the switch to the engine block the see if you have 12V with the key off. If not, chcek the same point on the switch to the neg batter terminal. If you get 12V there and not on the engine, you are not grounded at the engine, although the starter mount bolt should provide that. If the above check ok, then I would check for 12V at the starter solenoid "S" termianl when the key is turned on. An easy check is to jump the 12v+ cable on the solenoid to the "S" terminal with a screwdriver, that should crank the engine if the battery is not dead.

[Bob R.]

Re: 63 Ground strap education

The correct engine ground for the 63 is driverside engine mount front bolt to the front of the engine mount bracket on the frame. You should find a hole there from the original installation.

[Steve D.]

Re: 63 Ground strap education

Bob

The Corvette Central catalog says two engine mount straps are required for 63, and in the illustration each is configured a bit differently. Does this make sense?

Steve

[William C.]

Re: 63 Ground strap education

All of those ground straps are part of the U-69 (radio) package. They are not required for the system to function in running the engine.

[Steve D.]

Re: 63 Ground strap education

Bill

Brand new battery. I checked voltage from the hot lead on the switch to the negative pole on the battery and to a point on the engine (exhaust manifold bolt) and both showed 12+ volts. I'll jump the solenoid this evening and see what happens.

Steve

[Tom D.]

Re: 63 Ground strap education

The 63 service manual has a good simple diagram.

Tom D.
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