Checking Ignition Leads

[kopper69]

If you car is having a really rough idle chances are you have a loose or faulty ignition lead. Checking the ignition leads is really easy and anyone can do it, it only takes a few minutes.

Tools required: Multimeter

If you dont have a multimeter go and get one. You will use it, you can fix any electrical problem with it. A cheap one from dick smith
http://www.dse.com.au/cgi-bin/dse.storefront/43a48eb60b009c12273fc0a87f9c0717/Product/View/Q1467
will set you back $17 and will do everything you will need.

So....

Find the DFI module on the top of the engine on the passengers side. You want to pull just one of the ignition lead connectors of. Start any side, you will check them all but we will only do one at a time. When pulling an ignition lead off, grab the boot (the thicker joining part) of the lead (as shown in the photo). Dont pull on the lead itself as this can damage it.

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Now inside this plug is the metal connector. Make sure you see this because in a few minutes you will need to connect to this:

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Now that you have disconnected one side of the leads follow it to its other end. It will go down one side of the engine where it connects to a spark plug. You will need to disconnect the other side, again disconnect the lead by pulling the boot, not the lead.

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This is the multimeter i keep in my car, the same cheap one i showed you before. To use the multimeter turn it on and select ohms (the little ohmega symbol). To make an accurate reading turn it to the 20k (20,000) selection.

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Now put the two leads from the multimeter in each end of the ignition lead. It doesnt matter which lead goes into which end. Make sure you connect to the METAL PART inside the end of the ignition lead that we looked at before.

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If your multimeter reads 1 to the far left of the screen then the reading is too high for the 20k range, so change the multimeter to the 200k range and see if you get a reading then. If you dont make sure that the multimeter probes are touching the metal part.

Now the reading on the multimeter will tell you the resistance of the leads. The gregories manual for the VR/VS commodore recommends that the leads marked 1,3 and 5 be less than 17k (17,000 ohms) - 17 on the multimeter. The other three leads 2,4 and 6 should be less than 25k (25,000 ohms) - 25 on the multimeter. If you are getting readings that are higher than these figures you should replace the lead. I dont think you can buy a single lead for a VR/VS commodore from supercheap, so you may have to get a new set, which contains 6 new leads at a price of around $50.

When putting the lead back on make sure it is nice and tight and doesnt come off too easily. I have found that some of my leads were loose at the spark plug end, so I got a pair of pliers and put a bit of pressure around the metal connector. This warped the metal inside the lead slightly and gave me a nice tight fit on the spark plug.

Also note that you should only do one lead at a time, to prevent confusing the leads and plugging one back in the wrong spot, which can cause damage to the engine.

This guide has been created using figures for a VR/VS V6 commodore. The 17k and 25k resistance quoted should only be used when making measurments on a VR/VS commodore. The resistance may be the same for different series commodores but I am not sure, maybe someone can shed some light on this.

 

[fitzy2005]

spot on when i change or test leads i tend to reset the computer too just to be sure

 

[sedate looking]

Good article mate, not many people know you can check the resistance of leads to see how they are going.. Well done!!!

 

[dartwolf]

spot on when i change or test leads i tend to reset the computer too just to be sure

I have just brought a VP Commodore and was wondering how you reset the computer in them???

 

[Marty's_SV6]

I have just brought a VP Commodore and was wondering how you reset the computer in them???

Just disconnect the positive terminal lead off the battery for at least 5 minutes.Also remembering that by doing so you may need to enter a pin into the radio if its still the original one.
After re-connection start the car and rev the Engine to about 2000revs for about 30 seconds.
This action resets the computer in all Models up until and including the VY, not sure about the VZ.

Cheers :yeah:

 

[kopper69]

You can reset the ecu simply by disconnecting the 20A engine fuse near the battery for 10 seconds.

 

[chick in the sticks]

thanks very much

 

[crazymate]

If you do need to buy a new lead, i know that repco do sell them individually, however im not sure of how good a quality they are, (but it would do as a temporary fix until goods ones can be found.)
Also im pretty sure most supercheap stores have the bosch leads individually, but they are usually just on a rack and you have to search thro them all to find the right one.

 

[mld1]

Any one know the readings for a 98'model VT V6 ecotec

 

[spanks]

Another way to check for faulty leads is to run the inductive pick up of a timing light over the leadsbut dont connect it)and if the light is activated then you know that the leads are leaking.
But the multimeter is the acurate way