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Triumph TR6 - can't start
|My TR was running fine until today when I decided to replace the advance springs in the distributor. I rebuilt the dist about 4 years ago and noticed that the springs were in bad shape and finally came across some NOS spring set.|
After replacing the correct springs (large and small) and installing the dist in the correct orientation, I am now not getting any spark any more and hence the car cranks but does not start.
As far as I can see everything has been put together in the correct place and I tested for conductivity the 2 low tension wires (they are fine). it does not appear that I am getting any voltage off the coil ie at the + and - points.
Any help in trouble shooting and places to check for voltage would be most appreciated.
After a couple of hours I am totally stumped
|If you removed and reinstalled the points, you may have gounded them inadvertently (insulating washer in the wrong place). I've done this twice (my excuse for the 2nd time: 30 years since the last time), and every time it's like "DUH!".|
Do you have the Lucas fault manual.PDF?
Gives you diagnostic procedures for most LUCAS problems. Will e-mail to you...will be slow as it is 6MB. Contact me off line..remove AT and DOT from my e-mail.
I agree with Tom as a good starting point to check.
You say"does not appear that I am getting any voltage off the coil ie at the + and - points."
There should NOT be any voltage off the - terminal of the coil.
Place Red Voltmeter lead on + terminal of coil and Black lead on ground point (Neg Battery is best). Points should be closed turn ignition to ON not start. Volt reading should be battery (approx. 12V).
If 12V this is good.
Pull HT lead off the distributor and place .25" from clean area of the block. Crank the engine over..you should have spark.
|I don't know if this is helpful, but... My car stopped one day and three hours of troublshooting later I discovered a cracked rotor. The spark was shorting to ground from the rotor contact to the dist shaft.|
1. check for 12v @ coil positive with ignition on
No: find out why not
2. With ignition on, ensure points are open, check for 12V @ points.
Yes: goto 3.
No: wire from coil to points might be shorted to ground or coil might be faulty.
2a. Disconnect wire from coil to dist and check for 12V @ coil terminal
Yes: repair short to ground
No: Replace coil
3. Close points, check to see if voltage on points goes to 0V
Yes: goto 4.
No: clean or replace points
4. Pull coil wire from center of distributor cap, place it so the end is ~1/2 " from ground (engine block). Spin the motor over, is there a spark? (careful here it is easy to get zapped)
Yes: goto 5.
No: Replace coil
5. Replace the coil wire back into distributor. Pull one of the spark plug wires off a spark plug. Repeat the procedure you did with the coil wire, is there a spark?
Yes: Goto 6.
No: replace rotor
6. Check timing and firing order. It should be 4 degrees BTDC to start with
Here's another favourite, did you put the rotor back? I don't know how many times I've worked on the dist and forgot to put the rotor back. Something else I've seen is dirty points. How old are they? I once had the carbon contact fall out of the center of the cap.
|Tried the sequence of events.|
The thing that does not happen is #3 on Don's list (I get 12v whether the points are open or closed) and I do not get a spark when I detach the HT lead from the dist on both Ricks and Dons list
Possible coil problems?
The strange fact was that the car ran fine until I took apart the dist to replace the 2 springs. Coincidence that the coil packed it in?
|Don, re: the "did you put the rotor back" thing..|
Yeah, I've done that too..it's a wonder I haven't killed myself working on cars.
If the voltage at the points, from the coil, is at 12V whether the points are opened or closed would mean an open circuit.
The points are supposed to ground the - (Neg.) side of the coil when they are closed. This is when the primary windings of the coil begin to flow current and "charge" the primary side of the coil. When the points open the current flow stops and the magnetic field that was generated during the current flow collapses and induces a voltage on the secondary windings of the coil. The secondary windings have more coils of wire than the primary side which steps up the voltage to much higher level...like a step-up transformer. So, it's the opening of the points that genrates the high voltage in the secondary windings which produces the spark at the rotor which is routed to a spark plug.
I hope that makes some sense and help you diagnose your problem. Sometimes a little background on how it works helps. Also, you may find a better more detailed explantion of how an ignition coil system works if you search Google or something like that. All ignition systems with a coil and points are basically the same.
|HP Henry Patterson|
Henry has the point. Double check Tom's very first post.
This thread was discussed between 18/08/2006 and 19/08/2006
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