Ignition System Protection for Cranking, no start

[dkcase]

What is your opinion of this?

Is it necessary to disable the ignition on the car to do compression testing ? Car is my daughter's 94 Cavalier. It has a coil pack and plug wires.

My concern is, will I damage the ignition system if I only pull off the wires, and remove the plugs.

I am thinking I should run a shorting wire to ground from each boot; is that advised?

What I want to do is check compression in no. 4 cyl. because it is losing coolant and I see some seepage there on the exhaust side from under the head. I don't see any other leaking. She suffered a blown radiator hose recently and it may have caused this damage.

If there's low compression and I conclude the head gasket is damaged into the chamber, it's a new head gasket.

If it's holding compression, and it may be only leaking outwards, I may try a sealer... Bar's Leaks' Head Gasket Repair. Anyone tried that stuff ?

She wants to get rid of it anyway, or I wouldn't consider the "metal in a bottle."

Thanks.

 

[TheLoneRanger]

Yes, just disconnect the coil pack. That way the coils themselves won't be energized. If you pull the plug wires, the coil energy has nowhere to go, and might feed back into the PCM (or whatever Chevy calls it).

Does it blow white smoke upon start-up? Chances are it's blown into the cylinder, but it may not be too bad just yet.

Sorry, I've never tried the repair in a bottle.....

 

[Gary Allan]

I'd also unplug the injectors. We just did a compression check on a null and void 60's Chevy and with the plugs out the fuel was spraying out the cylinders without the gauge in it. Luckily the guy had a retro fitted HEI in it and we just unplugged the 12v lead to it.


Do you have a remote starter switch? That should bypass any ignition switched system (fuel pump, coil, etc.).

 

[Matt_S]

Isn't is possible to unhook the wiring harness from the coils? I'd think that would be the best way. You wouldn't have to worry about damaging coils or spark plug wires as you pull them off. If that's not viable, I don't think there would be a problem with simply removing the plug wires.

 

[kevm14]

Pull the fuel pump fuse. I personally have a problem with cranking when the injectors are firing but the ignition system is not. You can crank away all day long with no fuel in there, and the plugs firing won't hurt a thing.

 

[SHOZ]

Pull the PCM fuse. No spark and no FIs no fuel pump.