Symptoms of a Bad spark plug wire

[mkeleher]

Gentlemen,

Can you tell me the results of a bad spark plug wire? I have the following readings on my spark plug wires which makes me think this might be the reason my motor wont run past 4000 RPM's. #1 3440 ohms #2 3350 ohms #3 3350 ohms #4 3350 ohms #5 3420 ohms #6 10 ohms.

 

[mercurymang]

Re: Symptoms of a Bad spark plug wire

Seems strange to me. Usually the resistance goes up on a bad wire, not down.

 

[mkeleher]

Re: Symptoms of a Bad spark plug wire

3000 ohms is average for spark plug wires correct? It seems strange to me that 5 plug wires are all comparable and one is WAY different. What symptoms if any have you seen with bad plug wires

 

[jimmbo]

Re: Symptoms of a Bad spark plug wire

Maybe the meter is reading it as 10k?

 

[mercurymang]

Re: Symptoms of a Bad spark plug wire

Usually they go infinite (broken connection). Honestly, I have hardly ever had issues with wires. It's always the plugs or the cap and rotor. But I would say that a wire with that much of a difference is an issue. You really need a spark plug tester. If that one doesn't test right, swap the wire and see if the problem moves.

 

[Chris1956]

Re: Symptoms of a Bad spark plug wire

Outboard spark plug wires are solid stainless steel. Resistance should be zero. Anything else is bad. You are just measuring the wire right?

 

[mkeleher]

Re: Symptoms of a Bad spark plug wire

set on 20k with the meter all the spark plug wires (taken off the plug and coil) read .334 One of the wires reads .001. All the other wires that read about the same are 9" wires. The one wire that reads .001 is a 7" wire that looks pretty worn down.

 

[Chris1956]

Re: Symptoms of a Bad spark plug wire

How old are the wires? Maybe the springs are corroded? SS wire can go bad and get corroded as well.

 

[mkeleher]

Re: Symptoms of a Bad spark plug wire

5 of the wires are newer and blue, The other wire looks older and is black. Looks like a spare was laying around and someone threw it on there. If there motor is only running on 5 cylinders would its peak RPM's only be 4000?

 

[Chris1956]

Re: Symptoms of a Bad spark plug wire

Is it possible a prev owner put some type of automotive wires on it? There is no way to predict RPM on 5 cylinders.

 

[oldman570]

Re: Symptoms of a Bad spark plug wire

As Chris thinks: I do also. If the 5 wires are blue and the one is black then the reading you are getting would be about right as the blue wires use a carbon string for wire and the black one is metal core wire that is normally use on older outboards. The newer wires are not made to work in the environment as the solid core ones are. JMO
Oldman570

 

[Bob_VT]

Re: Symptoms of a Bad spark plug wire

Check ALL your ignition wires actually ALL your wires. Merc's are notorious for wiring going bad, cracking and corroding. Your wires "screw"into the connectors and those ends do go bad. Are you running electronic or distributor?

One of the EASIEST wire tests is to start the motor in total darkness You will see a spark jumping if it is bad.

You need to dig deeper into the diagnosis

 

[Chris1956]

Re: Symptoms of a Bad spark plug wire

Hey Bob, just caress the wires softly day or night, and you will know if they are leaking voltage..... I recommend the lightest of carresses, at least at first....

 

[mercurymang]

Re: Symptoms of a Bad spark plug wire

Outboard spark plug wires are solid stainless steel. Resistance should be zero. Anything else is bad. You are just measuring the wire right?

I did not realize this. I looked through my manual but couldn't find anything on wire resistance.

thanks. Learn something new everyday.

 

[mkeleher]

Re: Symptoms of a Bad spark plug wire

put the wires on today and motor would not run over 4000 RPM's and was very doggy out of the hole as usual. So at this point I have new plug wires, new spark plugs, a new stator and rectifier which now has the battery charging and the tach working correctly. I double checked today to make sure I had spark with a spark tester from the spark plug wires to the spark plug and I have solid spark on all. Checked compression and I have 115-110 accross the block. What would be my next point to investigate on this motor? I would hate to take it to a tech since I have already gotten this far into it.

 

[Chris1956]

Re: Symptoms of a Bad spark plug wire

OK, is it an inline 6 motor? Does it have a distributor? What year?

 

[Faztbullet]

Re: Symptoms of a Bad spark plug wire

If it has blue wires they or either Mallory replacements(9-28006) or Merc Hi-po replacement with have NGK molded into boot cover. You have a injector/s,ECU or TPI problem.

 

[mkeleher]

Re: Symptoms of a Bad spark plug wire

Is there a way to test the TPI?