Why Ground Plugs?

[ShellBack101]

Quick (possibly dumb) question, when doing the Joe Reeves WOT Timing procedure it mentions putting plugwires on a gap tester. What is the reason for not just letting the plug wires hang there as long as they are not touching any thing, do they need to be grounded to something for resistance or to prevent damage from too littel resistance?!?!?

 

[Barnacle_Bill]

Re: Why Ground Plugs?

If you are talking about checking for spark the base has to be grounded to complete the circuit.

 

[HighTrim]

Re: Why Ground Plugs?

I cannot speak for Mr Reeves, but short of saying if Joe says it, do it, it seems to me that the spark tester is needed for most timing lights to sense a charge traveling though the wire. Seems likely that Mr. Reeves would anticipate that only a inductive timing light would be used for the aforementioned test.

It is good to have all the wires connected on your tester to see that all cylinders are firing anyways. The multi way spark testers are ideal for this, you can purchase one or simply make your own.

 

[BF]

Re: Why Ground Plugs?

spark plugs are grounded by their threads, so yes, as said, you need to add a ground (aligator clip) or whatever from the threads to a ground if they are unscrewed. For a quick test, you can sometimes lean the plug ground electrode on a bare bolt. A benefit of a spark tester is that by expanding the gap, you can tell how healthy the spark is. You can make one with 2 nails, a piece of scrap wood, and an aligator clip.

 

[F_R]

Re: Why Ground Plugs?

Joe should answer this, but just as general information, cranking or running a motor with disconnected spark plug wires is torture on the coils. Good way to test a coil though. If it arcs through the side, it is no good. At least now it isn't.

 

[iwombat]

Re: Why Ground Plugs?

It's also a good way to keep stuff from going FOOM!

You've got fuel vapors coming out of those plug holes. A mis-placed spark is a very rude surprise.