Running short

T

treoleileagh

Full member
Location
Australia
My 79 Jota, runs on 1 and 3.  No spark at Nr 2.
I've got voltage to the nr 2 coil with key on.
The coil checks out at 45 ohms across the terminals and around 15,000 at the plug connector. I don't have specs for the coil but I think the coil must be capable of sptting a spark.

The ballast resistor is newish.

Not sure where to go next. This is a BTZ system. The BTZ box? What's the best procedure to test it?
Thanks everyone.
 
Check "-" side of coil when cranking/running for coil trigger. An LED test light works best. No coil signal poss due to box or faulty wiring/degraded insulation.
 
chrisk said:
I always thought ohms were overrated.
Check HT wire on 2, and plug. ;)
Click to expand...

Can the leads be removed from coils for replacement? I'm planning to check the trigger box tomorrow. If it proves good, the plug wire would be the next suspect wouldn't it? When I look at the coil I'm wondering how the wire connects underneath the external coil coating?
 
treoleileagh said:
Can the leads be removed from coils for replacement? I'm planning to check the trigger box tomorrow. If it proves good, the plug wire would be the next suspect wouldn't it? When I look at the coil I'm wondering how the wire connects underneath the external coil coating?
Click to expand...

Never tried, that stuff it?s tough as old boots.

Do you get spark if you pull the plug out, earth it out solidly and turn it over? See what happens. Maybe you have spark, but with a big hole in centre piston you?ll never get 2 to fire. I?m just the messenger, don?t shoot me.
 
chrisk said:
Never tried, that stuff it?s tough as old boots.

Do you get spark if you pull the plug out, earth it out solidly and turn it over? See what happens. Maybe you have spark, but with a big hole in centre piston you?ll never get 2 to fire. I?m just the messenger, don?t shoot me.
Click to expand...

Nope, no spark and a very shiny wet plug. That big hole thing ..? No thankfully. Too much compression. Defnitely an electrical issue.

Has anyone changed the plug lead on an ND coil?
 
treoleileagh said:
Has anyone changed the plug lead on an ND coil?
Click to expand...

All credit due to John Wilson (IIS)
------------------------------------------------------------

Replacing HT cables on Nippon Denso Coils
(pinky-biege colour, stamped 028700.)

First, carefully remove the epoxy resin around the HT cable entry point on the body of the ND coil.  You can do this, for example, by using small side cutters.  Take care not to damage the body plastic.

There are two parts to the HT lead:
? the inner HT lead/copper wire with insulation cover
? an outside thin sheath.

Pull hard on the HT lead until it comes out of the coil body. This will leave the outer sheath still inside the coil body. Break this bond by carefully pushing a screw driver down between the sleeve and inner bore of the tube until you feel the remaining epoxy, then continue working around the sleeve until it frees from the bore.

There is a standard spike termination at the end of the bore.  Insert a good quality copper core HT lead of 7mm diameter (8mm will not fit) into the bore (tube) until is stops.  Then secure the new lead to the ignition coil body using a good quality silicon sealant or epoxy. 

Do not use building grade silicon as it cures by liberation of acetic acid which attacks copper components.  Instead, use a neutral cure silicon such as 738RTV.  You can find it at the local electrical wholesalers; similar products are becoming more available from hardware stores. 

Once done, terminate the HT leads using NGK spark plug covers with 5.0K ohm suppression resistor for clean firing of the spark plugs.

IIS information sheet.
updated 5th January 2004
 
Is the non sparking shiny wet plug the original plug from No2 cyl or a new one?
Have you removed the plug cap & checked if there is spark between the HT lead & casing of engine.
You can also re terminate the HT lead by cutting about 6mm off the end till you get good copper core then try for spark.
HTH
Graham
 
Check the trigger coil resistances and compare - their wiring is susceptible to deterioration after 38 years
Swap the BTZ boxes over and see if No2 then sparks.  That'll prove the box
Swap or substitute the coil similarly.
All much quicker than buggering about with HT lead replacement! 
The ND coils are pretty reliable, as are BTZ boxes in my experience
 
Thanks for these suggestions. I haven't taken these steps yet. Swapping the boxes around is a good idea
I havent tried to short the HT lead directly. I had an idea that doing that risks damage to BTZ components?



 
use a junior hacksaw to cut the lead off flush with the face of its "socket" on the coil body, shave a bit of the body as well, then using a cordless drill and a 3mm bit, gently drill down the outside edge of the copper core, wang the drill around a bit after about 4 or 5 holes, pick the debris out with your wife's eyebrow tweezers, pick away, use the drill a bit more (maybe) and eventually you will expose the spike at the bottom of the pit, install new HT lead by first "spiking" the copper core end with a nail or some such to give you an indent to start the contacting bit, smear the outside of the new lead with araldite and then  push it in, clean the excess with a cloth moistened with thin oil and wait overnight for the finished article.
Done it loads of time and is very worthwhile.
CLEM
 
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