How to test ignition wires / plug connectors
11-15-2023, 07:27 PM
#1
Burning Brakes
Thread Starter
How to test ignition wires / plug connectors
Ok so you may recall my ignition issues back in September - just in time for the Rennsport roadtrip. Sidenote: car running perfectly again once I got all the ignition stuff replaced.
So I have Clewett wires on the car now.
I have the old Beru set. I have replaced 3 or 4 of the connectors since putting that wire set on 5 years ago.
My ignition issue seemed to involve heat - as the car would run fine for a bit before hesitating. I think the heat would build up (increasing resistance?) and cause the problem.
I'm sure most people would just toss the whole thing in the trash. But _I_ would prefer to keep a few good wires and/or connectors as spares - for roadtrips etc.
So. How do you (can you?) test these (resistance I assume) knowing/thinking failure requires heat?
Do you put them in the oven at 200 degrees (or some temp low enough to not melt anything but high enough to cause an issue??) for a bit then test??
Is there anything different about testing the plug connectors (compared to testing wires)?
Thoughts?
Thanks-
Brandon
'91 Turbo
So I have Clewett wires on the car now.
I have the old Beru set. I have replaced 3 or 4 of the connectors since putting that wire set on 5 years ago.
My ignition issue seemed to involve heat - as the car would run fine for a bit before hesitating. I think the heat would build up (increasing resistance?) and cause the problem.
I'm sure most people would just toss the whole thing in the trash. But _I_ would prefer to keep a few good wires and/or connectors as spares - for roadtrips etc.
So. How do you (can you?) test these (resistance I assume) knowing/thinking failure requires heat?
Do you put them in the oven at 200 degrees (or some temp low enough to not melt anything but high enough to cause an issue??) for a bit then test??
Is there anything different about testing the plug connectors (compared to testing wires)?
Thoughts?
Thanks-
Brandon
'91 Turbo
11-17-2023, 01:23 AM
#2
Instructor
Wire itself should be nearly zero resistance over these short lengths.
However the connectors have resistors in one end which should be 3kOhm total. And 1kOhm for the coil to distributor.
To test leads visual inspection for cracking then a test using a megohm meter at voltages over 1000VDC on a conductive surface. This however is still not enough voltage to really test the insulation, you would likely see the broken insulation before this test identifies a breakdown in insulation. Mostly due to the fact that the contact area with the conductive surface is minimal. And really once you’ve gone this far just replace the cables with new into the original boots if they check out.
Connections to spark plugs should be clean and dry, only use dielectric grease on the boots to help them seal.
The thimbles on the spark plugs threads should be checked for tightness. I once chased a intermittent ticking at idle to find a loose thimble on the threaded spark plug post.
I also noticed that the rotor in the distributor was sitting low in the notches under the distributor cap. This is evident when looking at the old one and seeing the burn line low down. A small tight fitting rubber washer moved it up into the sweet spot.
There is also a long forgotten fact that you should send a few drops of oil into the Center of the ignition rotor shaft through the felt material plug when replacing the rotor. Replace the felt plug once complete.
However the connectors have resistors in one end which should be 3kOhm total. And 1kOhm for the coil to distributor.
To test leads visual inspection for cracking then a test using a megohm meter at voltages over 1000VDC on a conductive surface. This however is still not enough voltage to really test the insulation, you would likely see the broken insulation before this test identifies a breakdown in insulation. Mostly due to the fact that the contact area with the conductive surface is minimal. And really once you’ve gone this far just replace the cables with new into the original boots if they check out.
Connections to spark plugs should be clean and dry, only use dielectric grease on the boots to help them seal.
The thimbles on the spark plugs threads should be checked for tightness. I once chased a intermittent ticking at idle to find a loose thimble on the threaded spark plug post.
I also noticed that the rotor in the distributor was sitting low in the notches under the distributor cap. This is evident when looking at the old one and seeing the burn line low down. A small tight fitting rubber washer moved it up into the sweet spot.
There is also a long forgotten fact that you should send a few drops of oil into the Center of the ignition rotor shaft through the felt material plug when replacing the rotor. Replace the felt plug once complete.
11-18-2023, 03:59 PM
#3
Burning Brakes
I'd first do the resistance test with your favourite (reliable) multi meter. Check that they are within the noted tolerance - any major discrepancy should be immediately obvious from wildly varying readings.
I recently threw away a couple of Beru leads on my Cosworth YB motor because they were showing 10 or 15kOhms compared to the standard-ish 5k. No need to test those leads any further when they were so far out. Ended up replacing them with other (old, new stock) Beru leads which I got at a discount because the HT lead was missing (not needed in my case as I have that motor converted to wasted spark).
I recently threw away a couple of Beru leads on my Cosworth YB motor because they were showing 10 or 15kOhms compared to the standard-ish 5k. No need to test those leads any further when they were so far out. Ended up replacing them with other (old, new stock) Beru leads which I got at a discount because the HT lead was missing (not needed in my case as I have that motor converted to wasted spark).
01-08-2024, 10:56 AM
#4
Rennlist Member
Another tool I can't live without. Although I wonder if the cables are only part of the issue. CIS can be a bitch. It could be any number of combined issues sometimes. I have seen cables arching so badly you can see it in low light on N/A engines and it did not cause excessive hesitation, although they are dual plug.
https://www.summitracing.com/parts/s...BoCSq8QAvD_BwE
So sad that we need Youtube to diagnose anything these days. Had nothing but hopefully a Chilton's or Hane's manual learning about these. I find more times than not YouTube is a waste of my time and the people posting are clueless giving nothing more than the most rudimentary explanation about the basics I already understand. If I can't think it through which is rare the info I need is rarely to be found.
https://www.summitracing.com/parts/s...BoCSq8QAvD_BwE
So sad that we need Youtube to diagnose anything these days. Had nothing but hopefully a Chilton's or Hane's manual learning about these. I find more times than not YouTube is a waste of my time and the people posting are clueless giving nothing more than the most rudimentary explanation about the basics I already understand. If I can't think it through which is rare the info I need is rarely to be found.
01-08-2024, 12:48 PM
#5
Burning Brakes
Thread Starter
Ahh cool tool - had never seen one of those. Of course I have still done nothing with these old plug wires.
You tube is hit and miss for sure. Bigger problem is "people" - or bots or scammers to trolls like Hdhsds who have nothing to contribute and just waste time/space here.
Forums are great for exchanging info with others you build trust with. And are usually fun.
Thanks Anthony
Brandon
'91 Turbo
You tube is hit and miss for sure. Bigger problem is "people" - or bots or scammers to trolls like Hdhsds who have nothing to contribute and just waste time/space here.
Forums are great for exchanging info with others you build trust with. And are usually fun.
Thanks Anthony
Brandon
'91 Turbo