weak spark

[Offshore]

A lot of you will have been looking at my "not starting" thread. We seem to be coming down to electrics so I am posting here.

Engine turns over fine and both battery and starter motor are new. Spark at the spark plug according to father in law is nothing to write home about. Spark from king lead off the coil is "a wardance" which translates meaning a good and strong spark.

Since she stopped going I have changed the points condenser low tension dizzy cap and rotor arm. Have this morning put the old condenser back on and spark at plug is slightly better. Minimal spark across the points when opened manually.

Have taken apart and reassembled the condenser and points wiring where they all meet to check they weren't earthing. Used plastic link bushes that came with the points. All seems to be correct according to the manual.

Coil is original I think and 44 years old. Good spark off king lead so leaving that alone.

not sure about wires to the coil. Think there should be 2, one on each side? Got good spark off King lead so assume that ok.

Question is this. There is a green and brown wire and spade connector spare in the area of the coil and distributor. Is it spare or have I pulled it off something and not put it back? When tested with a multimeter there is continuity between that and a white and brown wire on the coil.

As Bmcecosse said the other day we are nearly there.

Any advice gratefully received.

[aupickup]

the brown green is for the oil warning light on the speedo
you have one for the pressure and one for the filter housing

[Offshore]

Please see my post Not Starting under mechanical.

Opening the points to 25 thou or so and bizarrely she runs sweet as a nut.

Two months of stress and depressed nights and she is back.

[bmcecosse]

So - it's going now? No harm is 25 thou gap -let it be !

[Offshore]

Yep she's going. Did 20 miles last night. Timing and mixture need fine tuning but off to work in her today.

Did you have a view on the 5.89 ohms reading on the coil I posted on my original thread?

[alexmcguffie]

Is the 5.89 ohms measured with nothing else connected to the coil? 5.89R will give a current of just over 2 amps which is a little low to my mind. 3 ohms is more like it, which would give 4 amps and a bigger spark.

Alex

[Offshore]

Hi Alex. Can't remember if anything was connected but will check again tonight as you suggest.

[alexmcguffie]

If anything was connected then it would have made the reading lower than 3 ohms (for a good coil) so something does look a bit suspicious....

Two resistances in parallel always measure a lower resistance than the lowest of the two individual resistances.

[bmcecosse]

Sounds like a 24 volt coil to me !

[Offshore]

Interestingly I measured the resistance across the coil terminals last night with all connections removed - 3.2 ohms. Thanks for that tip Alex.

I changed the coil for a new Lucas DBL105 racing coil I got locally. No DBL101s in stock at all in my slightly remote community.

Engine and exhaust note is definitely different - louder and she started this morning which was rather damp with no choke and I have a spare proven coil to boot.

New one is heavier than the old one and sounds like it has lot more oil in it.

[alexmcguffie]

Excellent!

Out of interest, did you measure the resistance of the new coil? I'm guessing at about 1.5 ohms which will give you a nice meaty spark.

[bmcecosse]

Racing coil...wow.... I suspect your high ohm reading was due to dirty/corroded connection. As Alex explained -anything connected across the coil would result in a lower reading - not higher. I too would be interested to know the ohms on that 'racing' coil! But in any case - your will definitely go much faster now........

[Offshore]

She's certainly noisier in a sporty way and bit quicker off the mark. Only a couple of quid difference but the wife has an issue with me buying gold blingy bits for the other woman, Martha and not her. Oops.

ohms reading on the racing coil is 3.2 same as the old and now spare coil.

Starts with little or no choke which is interesting. Bit lumper but need to get the timing checked by garage on a strobe.

As for going faster got an indicated 70 last night before backing off and actually overtook someone this morning on the way to work. Now that was good for the soul

Thinking of opening the plug gaps to 30 thou as it might improving combustion and economy.

[bmcecosse]

Just twiddle the dizzy back and forth to get the best /smooth idle. A strobe won't tell you anything useful.... 30 thou gap won't help anything -and may make starting a little bit more difficult, although.....with a RACING coil.....