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TR6 No Spark at plugs

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TR6 No Spark at plugs
#1
  This topic is about my 1976 Triumph TR6
GeorgeC George Calcagnini
Palm Coast, FL, USA   USA
1976 Triumph TR6 "Charlie"
Well here I am. I am stumped. 1976 TR6 with breaker point ignition just stopped running on A1A, didn't do much other than remove the cap, poke around, and after about 30 minutes, looked in the dizzy again, and it started and ran well all the way home. That was the last time it started. I checked points, condenser connection, plug wire resistance, etc... and here's where I am 1 day later - nowhere. I have a solid dwell of 38 degrees, and all connections look good on the low voltage side. When I remove the center high voltage distributor wire and hold it near the dipstick handle I get a nice and regular spark. (btw, I tried a new coil). So I tried to test timing even though I am sure the dizzy wasn't moved...when I connected the timing light to plug #1, I had no light at all.... So I removed plug #1 wire and inserted a bolt into metal connector in the rubber grommet and held it up to the dipstick handle and got no spark at all...then I did it in the dark to be sure...still no spark. Resistance of the plug wire #1 and the others I tested was less than 1k Ohm. I spoke with Advanced Distributors this AM and he had me test to see if the rotor was grounded. It is not. Tested with ohmmeter first, then held the center high voltage wire to the rotor, no spark...so it is not grounded. I have new cap(s) and rotor(s) on order from Advanced Distributors. Currently have a Lucas cap and a red Advanced Distributor rotor. No sign of physical damage to either. My only conclusion is that the center dizzy cap plug is not touching the rotor to convey the spark to the plugs. or it is open circuited - it tests OK for continuity with ohmmeter. If the center wire has spark, how can it no be distributed in the cap??? I would appreciate any other things I could try while I am waiting here for new cap and rotor and grind my teeth. Thanks to all.

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tapkaJohnD Avatar
tapkaJohnD John Davies
Lancaster, Lancashire, UK   GBR
George,
As you have diagnosed, the problem seems to lie between the coil lead and the plug leads, which points to the dizzie cap and rotor arm.
Have you looked at the spring loaded carbon rod that sits in the middle of the cap, and contacts the rotor? They sometimes jam, or fall out!

John

GeorgeC George Calcagnini
Palm Coast, FL, USA   USA
1976 Triumph TR6 "Charlie"
Thanks, John. We're in sync. Just waiting for the "official" Advanced Distributor cap and rotor now. Was going to hunt locally for aftermarket parts but decided to let it sit and then put in the parts I know our 100% right. Yes, I checked the center post in the cap and it looks OK, I also checked continuity from the center post inside the cap to the center terminal on the outside and it is continuous... perhaps it is just not touching the rotor properly. Heading back to NYC on Thursday, so I won't be back in Florida with car for 3 weeks - hate to leave it on that note...I know it is going to bug me, but i guess it builds character.

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tapkaJohnD Avatar
tapkaJohnD John Davies
Lancaster, Lancashire, UK   GBR
I think you said you had a red rotor arm, but is it the real thing?
http://www.distributordoctor.com/red-rotor-arms.html

JOhn

GeorgeC George Calcagnini
Palm Coast, FL, USA   USA
1976 Triumph TR6 "Charlie"
Yep, it has the "AD" stamp on the bottom. made by Advanced Distributors. Very reliable company - spoke with them a couple of days ago. Very helpful...ran through some possibilities....good people.

barry s Avatar
barry s Silver Member Barry Stoll
Alexandria, VA, USA   USA
1972 MG MGB GT
1974 MG MGB
1976 Triumph TR6
1980 MG MGB
As you initially 'solved the problem' by removing and replacing the distributor cap, I think that you have a wire with and internal break or poor end connection. How about the point plate ground wire, which is quite thin and a bit fragile?

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
You could have carbon tracking. I line of carbon forms along the side of the rotor arm or inside the distributor cap (it looks just like a pencil line) and allows the spark to track to ground.

Just clean the rotor and cap with WD40.

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GeorgeC George Calcagnini
Palm Coast, FL, USA   USA
1976 Triumph TR6 "Charlie"
Thanks, Barry. My thoughts exactly, but after visually checking everything and testing all low voltage wiring, everything was found OK. Was originally suspicious of condenser which I had changed a month earlier to fix some misfiring. But after this inspection, I have a perfect dwell angle and get a perfect spark at my coil wire. So I think everything is OK on the low voltage side.

GeorgeC George Calcagnini
Palm Coast, FL, USA   USA
1976 Triumph TR6 "Charlie"
Tony, Thanks. When I inspect the inside of cap and rotor edge, I see almost no wear at all. Doesn't even look as if they are making contact - no carbon streaking or wear scratches...which makes me even more suspicious that the rotor and cap combo are not compatible - rotor not making good contact with cap contacts. That would explain no spark at the plugs despite having a spark at the center wire. can't wait to get the new rotor and cap from AD. If it still fails...I'll give up!

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GeorgeC George Calcagnini
Palm Coast, FL, USA   USA
1976 Triumph TR6 "Charlie"
All, Here is the solution! Received new capacitor and points from Moss yesterday, so rather than sitting around, I changed the easy one first - the capacitor. It started on the first crank! Wow. I totally discounted the low voltage side since I had a great dwell and spark at center high voltage wire. I assumed if I had a spark and good dwell that points and capacitor were operating properly. I need to go back to the books. Thanks to all who offered assistance. I'm sure I steered you wrong, but all's well that ends well. I'm all ears if anyone could help me understand where I went wrong in my diagnosis. Thanks, again.

barry s Avatar
barry s Silver Member Barry Stoll
Alexandria, VA, USA   USA
1972 MG MGB GT
1974 MG MGB
1976 Triumph TR6
1980 MG MGB
George - The rotor and cap contacts never make actual contact, by design. The spark from the cap contact jumps the gap to the rotor.



Edited 1 time(s). Last edit at 2018-01-28 09:36 AM by barry s.

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
When testing for a spark at the plug wires, you want to see the spark jump at least 1/4" to ground.

To produce a spark in the combustion chamber of the engine requires far more energy than in the open air.

GeorgeC George Calcagnini
Palm Coast, FL, USA   USA
1976 Triumph TR6 "Charlie"
Thanks, Tony. Couldn't understand why I could get that spark at the center wire on the cap, but not at the plug...so net of this was that I probably saw a weak spark that couldn't be replicated repeatedly in the cylinder...and the capacitor helps maintain the charge at the coil+ so that there is enough energy available to repeatedly fire the coil....reasonable?

glcaines Avatar
glcaines Silver Member Gary Caines
Hiawassee, GA, USA   USA
Also, the spark should be bright blue. If you see a weak yellow spark you have issues.



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