Correct Ignition Coil Resistance + Mixing HT Leads

[Fudgy666]

I'm currently trying to narrow down what I think is an ignition fault, and last weekend checked my Ignition coil.

I have measured the resistances across the terminals of the Ignition Coil and compared them to the values on Brickwerks (The same values as Haynes I think):

Ignition coil to suit early T3 models with non pin type fitting (DIN).

Test data.
Primary resistance [between terminals 1 & 15] - .52Ω to .76Ω
Secondary resistance [between terminals 1 & 4] - 2.4kΩ to 3.5kΩ

The Secondary resistance in 2.7kΩ, so I'm happy with that.

My Primary resistance is 1Ω, which initially I thought might be OK ?

But actually the 0.24Ω difference, although looking small, is quite a large percentage error (Somewhere is the ballpark of 34%)

Should this worry me, or is 1Ω actually OK ?

[tobydog]

Try touching the meter leads together on the low resistance range, you will probably get a low reading of a fraction of an ohm, subtract that from the primary resistance reading to get a more accurate value.

[Fudgy666]

Try touching the meter leads together on the low resistance range, you will probably get a low reading of a fraction of an ohm, subtract that from the primary resistance reading to get a more accurate value.

Nice one, I'll try that.

Cheers tobydog

[Fudgy666]

Also before I started getting a flat spot, I had replaced the HT leads, distributor cap & rotor arm with items from Just Kampers.



http://www.justkampers.com/ignition-lea ... d-t25.html

In the HT Lead set, the replacement lead from the Coil to the Distributor Cap wasn't long enough, so I didn't replace that one lead. I still replaced the 4 plug leads with new cables.

Is there any reason why mixing old/new HT leads would cause me problems ?

[what2do]

I do know of someone that bought the same ht leads from jk and one was faulty. Find the resistance per metre and then check them, nit a definitive test but it's a start.

[Fudgy666]

I do know of someone that bought the same ht leads from jk and one was faulty. Find the resistance per metre and then check them, nit a definitive test but it's a start.

Sounds like a plan. I'll give it a go (Now kinda wishing I hadn't thrown out the old HT Leads )

My only reservation is that, if only one of the plug leads was faulty, wouldn't this manifest itself as a misfire?

The engine seems to run smoothly right up until it hits the flat spot and dies

[HarryMann]

At what revs and load conditions does it manifest?

[what2do]

You threw out the old leads???? You ought to be banished to the facebook page for a period of not less than 14 days...

[Fudgy666]

At what revs and load conditions does it manifest?

At the moment it's hard to say 100%. I've run the van 3 times in the last couple of weeks and it's happened all 3 times.

Once was around 20 mins into a drive going around 45-50 mph in 4th gear on a flat road. Lost all power, pulled over and van restarted after 2-3 mins.

Second time I was returning from a 30 min drive, reversing onto my drive. Quite a steep drive, so always requires a bit of power. Same again, lost all power, but van started 2-3 mins later.

And I can't remember the conditions the 3rd time.

A number of reasons make me think it's connected to the ignition system.
1.) In March I had the Twin Solex Carbs refurbed in Chester at Gasure. Drove the 360 mile round trip with no problems. Noticeable running improvement on the way back as expected

2.) When the power cut out on my drive I got a strong smell of unburnt petrol around the rear of the van. So I'm pretty sure fuel is getting where it needs to go but not being combusted.

3.) All 3 instances have occurred since I replaced the HT leads, Spark Plugs , Distrbuter Cap & rotor arm during a routine service around 3 weeks ago.

You threw out the old leads???? You ought to be banished to the facebook page for a period of not less than 14 days...

I guess it's not a good time to admit I threw out the old cap and rotor arm as well.

[HarryMann]

Try another rotor arm?
Inspect all parts with a sharp and critical eye.. always first line of diagnosis. Looking for tracking ceacks anything untoward

[what2do]

No teaching you to suck eggs but have been and checked every lead is tight, the cap is on properly, etc.? Someone recently had a running problem and their rotor wasn't fully seated. I had an issue earlier in the year, checked everything apart from the obvious - one of the spark plugs was actually wobbly, it had come undone!!!

Ps. I know a chap on here that doesn't even throw away his old engine oil

[tobydog]

Had similar symptoms. Driving along and engine cuts out, will restart after a while. Happened two or three times, in the end no spark at all. Turned out to be the ignition amplifier, the one that I changed wasn't the original. Van is on the third one at least. Now carry a spare.

[Fudgy666]

Cheers for the ideas Guys.

Defo gonna get all C.S.I this weekend and break out the magnifying glass.



Fingers crossed I'll be able to narrow it down.

Ps. I know a chap on here that doesn't even throw away his old engine oil

Neither do I . . . . . . I just store it in small drops under my van on the driveway !!!!!!!

[HarryMann]

Yes ignition Amp would be another thing to substitute.

Don't forget theres a thing called co-incidence

So changing the leads n cap may have been just that. .

A co inside ance

[Fudgy666]

Had similar symptoms. Driving along and engine cuts out, will restart after a while. Happened two or three times, in the end no spark at all. Turned out to be the ignition amplifier.

Gave this a go being as the Ignition Amp on my Van certainly looked 30 years old and all the heatsink compound had long since crumbled away !

Replaced with one from Brickwerks:

https://www.brickwerks.co.uk/index.php/ ... -0-cu.html



Did a couple of test drives over the weekend (Around 45 mins worth) and the Van didn't cut out. So initial signs look promising.

Not going to hold my breath until I get a few more miles on the clock though.

Cheers for the heads up though