Resistance in spark plug wire

[520John]

Hi people.

Does anybody know what resistance (ohm) it should be in the spark plug wire (the one going from the coil and down onto the sparkplug)??

[shrike071]

Hi people.

Does anybody know what resistance (ohm) it should be in the spark plug wire (the one going from the coil and down onto the sparkplug)??

Depending on the accuracy of your meter - really, really close to zero.

[520John]

Depending on the accuracy of your meter - really, really close to zero.

I set the ohm meter to 200k and it measured 2,4????

[Ferret]

Spark plug lead resistances are generally very high iirc. Something about noise supression.

[520John]

Spark plug lead resistances are generally very high iirc. Something about noise supression.

So its ok with the 2,4 at 200K??

[Ferret]

yeah that means 2.4K ohm resistance, it's probably fine, though someone will have to find the stock spec for the leads...

[shrike071]

I remember something in the Bentley's about there being a .1 or lower on the M50's coil-on leads

[pingu]

I also seem to remember that spark plug leads have a resistance of a few kOhms. 2.4k sounds about right to me.

[AngryPopTart]

When I was researching the plug wires for my '89 with the M20, I was looking into making my own wires and had found a few places that sell the plug wire ends. The ends are 5000 Ohm resistance.

[stilljester]

Hi people.

Does anybody know what resistance (ohm) it should be in the spark plug wire (the one going from the coil and down onto the sparkplug)??

Spark plug wires: 0 ohms (appox.)
Spark Plug ends: 5.0 +/- 1.0 kohm

[520John]

Tnx a mill for all replies.

Does that mean that my wires are ok?
Just so everybody understand what I'm talking about:
I've lifted out the coil. Beneath the coil it is a approx 15cm long wire that I can pull off. Its the lead that connects the coil to the sparkplug. (my 520 has electrical ignition, not a distributor). I've measured the resistance in this wire.
I put my ohm meter on 200K and it measured 2.4 on all six wires.

Is this ok or are they fu****??
All six have taken a bath in oil (I have now changed the valve cover gasket but it will not ignite.)

[pingu]

Sounds like the wires are OK, especially as all 6 read the same. The resistances are used to reduce interference to radios.

If everything is soaked in oil thenth oil might have broken down (in the electrical sense) and the spark might be tracking across a carbonised portion - might not be visible.

Best to clean the oil off everything (before it kills your coilpacks), including the wires (try some sort of solvent for this) and try again.

[Morgenster]

I set the ohm meter to 200k and it measured 2,4????
Doesn't this mean resistance is around 400k ohm or am I horribly wrong?

[Bill R.]

m50, it depends on the spark plug connector you have. The bosch ones have a resistance of 1k ohms plus or minus 20%, the Bremi ones have a resistance of 1,8k ohms +-20%





Hi people.

Does anybody know what resistance (ohm) it should be in the spark plug wire (the one going from the coil and down onto the sparkplug)??

[pingu]

If the meter is on the 200k range then it can measure 0k to 200 kOhms. So 2.4 on that range is 2.4k.

With a 400kOhm resistor on the 200k range, it would show 200k - just as if it had nothing connected. By changing the meter's setting from the 200k range to the 2 MOhm (mega ohm) range, you'd then get a display of 400.

[520John]

The coils and plugs are giving sparks, in other words 2,4 at 200K is ok.

Now its down to changing the fuelfilter and trying again. If that doesnt work then I'll have to change the pump.
Do you agree that I have narrowed it down to these two possible faults??

[Dave M]

The coils and plugs are giving sparks, in other words 2,4 at 200K is ok.

Now its down to changing the fuelfilter and trying again. If that doesnt work then I'll have to change the pump.
Do you agree that I have narrowed it down to these two possible faults??

Not sure..........

Maybe I missed a previous post and am missing some background info. From what i gather, your head cover gaskets were bad, the plug wells filled with oil, shorted, and you lost spark. Now you've cleaned things up, changed the gaskets, have a spark, but no ignition. What are the odds that your fuel delivery is hampered just as you solve a spark issue? (Low??)

Is this the correct scenario?
Was anything else messed with (sensors etc.)?

If your spark IS strong enough, your sensors and DME are in working order, then rather than spending $$ on parts you may not need, test the fuel pressure. Regarding the DME, is it not possible that the oil in the plug wells could have damaged the coils, then the DME? Someone may know, based on the fact that you still have spark, whether this is possible.

Keep us informed, and good luck,

Dave M

[RallyD]

If the meter is on the 200k range then it can measure 0k to 200 kOhms.
With a 400kOhm resistor on the 200k range, it would show 200k - just as if it had nothing connected. By changing the meter's setting from the 200k range to the 2 MOhm (mega ohm) range, you'd then get a display of 400.

That is strange.
Changing the range settings on any meter should simply move the decimal point.
With the setting of 200K you should be able to measure up to 999Kohms.
A 400kOhm resistor measured on the 200K setting would show 4. on the display.

[pingu]

That is strange.
Changing the range settings on any meter should simply move the decimal point.
With the setting of 200K you should be able to measure up to 999Kohms.
A 400kOhm resistor measured on the 200K setting would show 4. on the display.

Nah, a 200k range can't distinguish between 200k and an open circuit (i.e. an infinite resistance). The maximum resistance a 200k range can measure is 200k. That's why it's called a 200k range.

When you talk about measuring up to 999kOhms you mean a 1MOhm range.

To avoid an incipient flame war, I'm talking about a Digital Multi-Meter (it is 2007 after all). On an analogue meter the concept of range is rather meaningless as the resolution simply depends on your ability to see a barely perceptible movement of the needle.