1976 Triumph Spitfire electrical no start

[Nigel Goodwin]

After looking at the schematic again I think the distributor probably does not use a normal mechanical set of points. The reason for thinking that this is the case is the item "drive resistor" that is connected to the distributor.

Good spot - there's also three wires going to the distributor, with points there would normally only be one.

A quick google seems to show that they introduced electronic ignition in 1975.

 

[KeepItSimpleStupid]

You need spark, fuel and air. Apparently your missing spark. Assume a coil and distributor, do you have spark at the coil?
Do you have power to the coil while starting and in the on position?

One interesting this is that the coil is powered directly from 12V when starting, so there should be a huff anyway when using starting fluid/
In the on position, the coil gets power through the ballast resistor.

 

[Donzoh1]

Same problem...different day? I didn't have spark at spark plugs and found the points closed. I set .015 gap but still no spark. I disconnected the battery and found continuity (11.2 ohms resistance) between the positive cable and the chassis which I think is wrong. Wondering whether I fried the ignition coil...which is a fairly new coil. Any suggestions are appreciated.

 

[KeepItSimpleStupid]

Check the primary resistance. There should be specs.

The ignition switch position should matter. I'm assuming that in the older vehicles the ignition was a high current device. It is not in modern cars.

START (no ballast resistor) should give you a lower resistance than ON (ballast resistor).

The coil being bad would not surprise me.

 

[Donzoh1]

I also figured out that the points had been closed and this a.m. the battery was dead. The points screw may not have been tight, i think. Usually, I disconnect the battery. Anyway, i measured coil primary resistance at 2.2 ohms. There is also an extra coil I got with the coil that measures over 6 ohms. I'm guessing these are both toast as max resistance is specified at 1.45 ohms. If I get a new coil, is there a way to measure input current to be sure it won't be destroyed as well or was the old one destroyed by the closed points? Also, the ignition light is on continuously when the battery is connected so I'm wondering whether that's part of the problem. I have gotten the car to fire successfully prior to this.

 

[KeepItSimpleStupid]

I also figured out that the points had been closed and this a.m. the battery was dead. The points screw may not have been tight, i think. Usually, I disconnect the battery. Anyway, i measured coil primary resistance at 2.2 ohms. There is also an extra coil I got with the coil that measures over 6 ohms. I'm guessing these are both toast as max resistance is specified at 1.45 ohms

Points closed overnight by itself no -- because the ignition switch should cut power.

It's difficult to measure resistances around 1 ohm. Your test leads might measure that. 1.45+x=2.2; x is vary close to lead resistance. The 6 is bad. The 2.2, can;t tell.

If I get a new coil, is there a way to measure input current to be sure it won't be destroyed as well or was the old one destroyed by the closed points?

You need to use a series resistor of a known value. At 14 V, you have about 1A with the standard coil. So, pick something like 12V and 0,.2A., so 2.4 ohms. 12/0.2 = 60 ohms. So grab something close with a wattage > P=VI (12)*.2 = 2.4 W,, so say a 5W resistor.
So 100 ohm 5-10W 1%, e.g. https://www.digikey.com/products/en...ity=1&ColumnSort=0&page=1&stock=1&pageSize=25

Now you can measure the voltage across the device (coil) and the current through the device. I=Vr/100 ohms). Vr is the voltage across the resistor.

Also, the ignition light is on continuously when the battery is connected so I'm wondering whether that's part of the problem. I have gotten the car to fire successfully prior to this.

I'm sure you mean the alternator light. I would assume that it goes out when the key is off?
[/QUOTE]

 

[Donzoh1]

I may have left ignition on all night...dunno. but, the alternator light is on whenever the battery is hooked up, key on or off. There's definitely something wrong there and I'm thinking the whole ignition circuit is energized whenever the battery is connected.

 

[Donzoh1]

Also, would you say the coil could still be functional if resistance really was 2.2 ohms even the spec is 1.45?

 

[KeepItSimpleStupid]

I may have left ignition on all night...dunno. but, the alternator light is on whenever the battery is hooked up, key on or off. There's definitely something wrong there and I'm thinking the whole ignition circuit is energized whenever the battery is connected.

That likely burns your points. i don;t have a schematic for your car, but just based on previous experiece:
1. Bulkhead connector (alternator lamp)
2. Voltage regulator
3. The light has to work, and it does

See: https://www.gomog.com/BLAIR/tech/melectrical/ign-light.html

 

[KeepItSimpleStupid]

I

Also, would you say the coil could still be functional if resistance really was 2.2 ohms even the spec is 1.45?

Your lead resistance is likely 0.5 ohms or so.

Delco ignition system - Wikipedia

en.wikipedia.org

You should be able to "play points" with the ignition on and the wire from the coil to the points disconnected. You will have the ballast resistor in place. Take a plug out and connect to just the HT side of the coil and ground. Briefly tap the the coil to ground a few times (the side that went to the points) . You should get a weak spark.

Capacitor
There is a capacitor (sometimes called a condenser) connected across the points. If the capacitor were missing or defective, the primary current would arc across the opening points allowing the current and therefore the magnetic field to collapse slowly causing a weak or no spark. When the points begin to open the primary current is diverted to charge the capacitor, checking the rate at which the primary voltage rises and limiting the arcing.

I'd suspect a shorted capacitor first. If you can disconnect the cap, you should get a weak spark.

The failures I used to see were do to dielectric breakdown in the coil. I converted a 1965 Ford in the mid 70's to electronic ignition using a version of the XR-700 https://mgaguru.com/mgtech/ignition/ig207.htm You HAVE to upgrade the wires.

Make sure you put the rotor back.

 

[Diver300]

The ignition lamp / alternator warning light should turn off when the ignition is off, as soon as the engine has stopped.

If it stays lit, something is wrong and you will get a flat battery quite quickly.

The fault could be a faulty ignition switch, or a faulty alternator, or a fault in the wiring. You would need to do further tests to find out which.

 

[Les Jones]

You still seem to be doing random tests that are not related to a logical approach to the problem. You seem to have started to look for a fault with the alternator and you don't seem to understand how the alternator system works. The thick wire to the alternator is connected DIRECTLY to the battery positive without any switches or fuses. There will be no current through this wire when the engine is stopped due to the diode pack in the alternator. When the ignition is turned on the alternator field is weakly energised by the current through the alternator light on the dashboard. With this small current through the field and the alternator rotating the field coil is energised more strongly via the regulator and the output from three diodes in the alternator. As soon as the alternator is giving an output the alternator light goes out as the field current is being fully supplied by the alternator. Back to your ignition problem. Does your distributor have three low voltage wires going to it as in the schematic from the link provided in post #2 or does it only have one low voltage wire ? Did you verify that the points were opening and closing by measuring the resistance between the wire from the distributor to the coil and ground (With the coil end disconnected..) as you turned the engine slowly with a spanner or pushing it with the car in gear. If the car has not been started for a very long time the points may need cleaning with very fine sandpaper. Describe EXACTLY the procedure that you used to set the points gap. Did you do the tests I suggested in post #20 and if so what were the results ?

Les.

 

[KeepItSimpleStupid]

Les Jones : Paragraphs? Otherwise good explanation. Sandpaper use is always questionable. 400-1500 grit, maybe.

The thick wire to the alternator is connected DIRECTLY to the battery positive without any switches or fuses.

There is usually a fusible link in that circuit. It can be nothing more than a short piece of a thinner wire.

One time, I had a really wierd issue. The car just stopped. A wire snapped off the rotor in the alternator. Because of a second proble, corrosion of the bulkhead connector, alt light circuit (guess), no light.

 

[Donzoh1]

If the coil has 2.25 ohms resistance (which is higher than the max spec or 1.45 ohms) will this prevent starting? Also, the pic here shows some corrosion or soot inside the distributor cap.

 

[Donzoh1]

 

[Nigel Goodwin]

If the coil has 2.25 ohms resistance (which is higher than the max spec or 1.45 ohms) will this prevent starting? Also, the pic here shows some corrosion or soot inside the distributor cap.

As you've already been told, that reading includes the wires as well - you can't generally measure low resistances accurately with a simple multimeter.