distributor ground wire 66 427 390 hp

[Harry L.]

I have just installed an ignitor II pertronix module to my breaker plate. There is a ground wire connected to a screw on my vacumn advance. Should I move that ground wire over to the the screw to the breaker plate where the module is ? Or does that ground on the vac. advance,ground what needs to be? thanks DUTCH

[William C.]

Re: distributor ground wire 66 427 390 hp

That screw grounds the plate. It needs to be attached so the plate is grounded, and anything you attach to the plate will also be grounded. If that wire breaks, you will have one H--- of a time figuring why the engine will have a spark on a timing light but will either not run or if it starts will run terrably and spit, backfire and stop on the road at unexpected times. Worst problem I ever had to chase on my wife's car.

[Harry L.]

Re: distributor ground wire 66 427 390 hp

Thanks Bill, I just was not sure if that vac advance ground, grounded the rest of the breaker plate. It is correct to say that it does. THANKS dutch

[Bill C.]

Re: distributor ground wire 66 427 390 hp

Harry,
I could be wrong, but I think with the pertronix module that ground wire is not needed, the module does not depend on a ground to trigger as a set of points does. Thats assuming its the 2 wire module, if its the one wire unit, it may still be required, you will need to check the wiring diagram that came with the unit.
Bill

[John H.]

Re: distributor ground wire 66 427 390 hp

From the www.vintageperformance.com/retrorockets site (distributor of Pertronix products):


<STRONG><FONT face="Times New Roman">Another thing that can cause a problem with an Ignitor is if there is a bad ground between the breaker plate on which the module mounts in the distributor and battery negative (assuming a negative earth system). With a digital ohmmeter set on its most sensitive scale, measure the resistance between the Ignitor mount plate and the battery negative terminal (the battery terminal itself, not the connector on the ground cable). If it is 0.2 ohms or more you have a bad ground. Check for corrosion at the connections of the ground strap between the breaker plate and the distributor housing and also at the battery itself or where the negative battery cable attaches to the block. Another possible resistance source is the distributor hold-down clamp which is the electrical connection between the distributor and block or intake manifold. If engine parts have recently been painted there may not be a good ground. 0.2 ohms may sound like a negligible amount of resistance, and in a steady state circuit it often is. But in an ignition circuit where the current is switched on and off many times a second, the transient effects of the 0.2 ohms is significant and can prevent an Ignitor from firing normally.

[Joe R.]

Re: distributor ground wire 66 427 390 hp

With a digital ohmmeter set on its most sensitive scale, measure the resistance between the Ignitor mount plate and the battery negative terminal (the battery terminal itself, not the connector on the ground cable). If it is 0.2 ohms or more you have a bad ground.

John,

I thought I might mention that a resistance this low is not as straightforward to measure as say 500 Ohms. For those who don't know, the way to do this is to first short the meter leads together, taking note of the meter reading. Then when you go to measure the resistance you are interested in, subtract out the leads.

For example:

The meter leads measure 0.2 Ohms. The circuit measures 0.3 Ohms. The actual resistance is 0.1 Ohms, which passes the test John gave above.

Joe