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78 Spifire ignition problem

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eejay56

eejay56

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Here is my symptom. After about an hour and a half of driving the ignition light begins to glow at idle. Relative to rpm, as rpm increases the light gets dimmer and goes out at about 2000. After another ten minutes or so the engine cuts out briefly a couple of times then dies all together. Trying to start it it will fire for a few revs then die. when it's in failure mode the ignition light does not come on when I turn the key on. After lifting the hood and waiting thirty minutes the ignition light starts to come on when the key is turned then it starts and runs fine. I thought the problem was with my coil but I swapped it out and it still happens. I plan to replace the cap, rotor and condensor but I wondered if anyone has experienced a similar problem and if I should be looking at anything else. The distributer is a 45D4 and the car has no emission stuff.
 
This sounds like an electrical problem to me--not really an ignition problem. I'd look for a bad connection somewhere. Also, battery or voltage regulator problems.
 
I first thought of an alternator problem, but the engine quitting sounds like something different.

The IGN light should glow when the alternator is not putting out enough amperage to charge the battery. So having it glow at idle would be a symptom of the alternator not outputting enough power. Also, having the light go out when RPM increases would fit, since the alternator would put out more amps at higher rpm.

The engine quitting, though must be something different. The alternator would not cause that. It occurs to me maybe you have an overheating problem. Your Spit, I believe, has the same belt driving both the alternator and water pump. Could it be the belt is slipping and causing the alternator problem and also causing the car to overheat? Do you get a high reading on your temperature guage?

I have seen problems in the past with ignition systems (although generally only with electronic ignition) that are heat related. Wait a half hour with the bonnet open and everything cools down, away you go.

There are only two wires connected to the IGN light. A brown/yellow from the alternator, and a white which also feeds other lights and comes off one side of the top fuse. The top fuse white wire also feeds the ignition primary circuit, so I guess its possible there is an electrical problem. But since it changes with time, I would look for something that also changes with time (like heat), bringing the problem on.
 
I wouldn't rule out a poor connection. Resistance (or conductance...depending on how you look at it) changes with temp.
 
I recently had some Spitfire alternator issues - and my best solution so far is to have a spare ready!

I learned that this particular unit should put out about 14.75V. You can simply check this with any voltmeter across your battery while the car is running. You do not have to rev your engine. It will make this power at idle. If you see any other voltage, for example I was getting 13.5V - your alternator is faulty(given it is the stock unit).
My strange symptom was the ignition light was on while the car was off.
My battery was reading about 12.5V with the car off as well.
Also, the car will start and run with the alternator disconnected. Perhaps you can try a few different things, and find the source of your problem, or get your battery tested for faults.
Good luck, I hope it's simple.


Adam H.
____________________________________________________________
1972 Triumph Spitfire.
 
I agree with the comments above. This sounds like a charrging sytem issue. Either the alternator or the wiring it at fault. Nothing in the ignition system would cause the light on the dash to come on - that's a charging system light.
jeff
 
At idle I read 14.2 volts across the battery and 12.8 with ignition off. That's with the engine cold not when it's failing. What would make my ignition light not come on when I turn the key on?
 
When you turn the key on (i.e. have not started the engine yet) the ignition light will come on. This is normal operation. At this point the alternator is not running and you have only battery-power.

Once the engine starts, however, the ignition light should go off, as the alternator is putting out more power than the battery. At steady idle (700-850 rpm) a charging voltage of 14.2 should turn the igition light off - however, see Adam's post above about alternator output voltage specs. Its possible that at 14.2V the light will still be on, but go off at higher RPM.

If you have a high impedence/resistance in the battery itself, I suppose you could still have an ignition light on at idle, since the battery won't charge easily. Also, if there is a heavy electrical load on the alternator (lights, maybe some high draw that is not tripping fuses yet) you could still have an ignition light.

If your ignition light is NOT coming on when you turn the key to 'On' (but engine not started yet), that is not proper operation.
 
Normaly the ignition light goes on when the key is on. After the car fails and won't start the ig light doesn't come on until everything cools down. After 1/2 hour with the hood up ig light comes on and the car will start. Temp guage reads good and engine is not overheating.
 
Also the battery seems strong and never has trouble cranking the starter.
 
Have you checked to see if you have spark when the engine won't start?

I'm wondering whether the ignition switch or the top fuse could be a problem. The distributor and the ignition lamp are on the same white-wire circuit that comes off one side of the top fuse. The coil is not on that circuit, but if the dizzy is not breaking then you won't have spark.

The handbrake warning light is also on the white circuit. When it is in 'won't -start' mode you could try pulling up on the handbrake and see if you get a dash Brake-Warning light as a way of testing that circuit.

It may be worth checking the connections at the top fuse (both sides of the fuse-holder clips) and also connection #3 on the igntion switch.
 
I haven't been able to check spark at the plugs because the one time I had someone with me to crank the engine I had no tools. I do get a spark at the points though. My handbrake light isn't very good for a test as it only works occasionaly (whether the car is running or not)My ignition switch is somewhat flaky and sometimes I have to jiggle the key, that is a different problem though because if that happens while I'm driving the tach dies.
 
Wow! It sounds like you might need to replace the ignition switch for starters! That's not good when the car dies and wiggling the key fixes it! That could be the problem, despite other characteristics like the tach not working. When the tach circuit dies, so does your power to the ignition coil (I believe). A bad ignition switch can also affect the amount of resistance through the circuit that allows your battery to charge. If nothing else, you have a compound problem and the ignition switch is likely one part of it!
Jeff
 
I would agree with Jeff. This can't be good. I would be having a real close look at the ignition switch (or replacing it) and also at the wires coming in behind the dash and into the steering column that feed the switch. You may be shorting out somewhere. But if the switch is bad it needs to be fixed or replaced before going much further.

Your tach gets its signal from the negative side of the coil (white/slate wire). The tach signal wire and the negative voltage wire from the distributor to the coil are common'd. The positive side of that circuit comes from connection 3 on the ignition switch. Jiggling the key should not affect the tach, they are not supposed to be directly connected. But if jiggling the key does affect the tach, then it would seem the only way would be through the white/slate wire off the coil. And the only way to get to that is through the dizzy and the primary ignition circuit. The signal wire from the tach only goes to the coil. It doesn't go anywhere else.

I would also check the wiring to the distributor carefully. The US '78s had an electronic ignition, which apparently has been replaced with mechanical. I would check the wiring just in case.
 
The switch is on my list. I've had the car 2 weeks and am still finding out what's what. The engine number indicates the engine is from a Dolomite Saloon. That may explain the mechanical dizzy. I was told all the reciepts were there but after going through them (I know, I should have done that before I bought it!)there is 10 year gap. No reciept for the engine, the Weber carb or the Lucas Sport coil. It also has all smog equip removed.
 
Sounds interesting.

Hopefully the wiring harness is a standard 78 Spit. Otherwise tracking down an electrical fault will be more difficult.

You may already have this but just in case, here is a link to some excellent wiring diagrams done by Tom O'Malley for the Spits. I have found there are almost always variations, depending on what has been done to the car over the years, of course.

https://www.triumphspitfire.com/wiring.html

I guess there may be one or two problems compounding here. I had a '75 Spit years ago that used to fail the way you describe (although not with the alternator light). After shutdown, it wouldn't start up. If I left it for a half hour, it would fire back up again. Drove me nuts. I finally figured out the heat from the engine was affecting the distributor electronics somehow and causing an open circuit. Cooled down, they ran fine again. Replaced it all with a Crane setup.
 
Don't get discouraged, EEjay!

Most times these electrical faults are an easy fix, but they just take time to figure out.
Try to focus on what you think the problem setting you back the most is. What makes this car unreliable? I think you need to look at the ignition switch first.

Adam H.
____________________________________________________________
1972 Triumph Spitfire.
 
I think I was wrong about it being an ignition problem. Now I believe it's the fuel tank venting. I pulled my vent hose off and tried to blow through it, no go. I traced it up to the engine compartment and it is folded over with a ziplock to hold it! Where should it go to?
 
Ok I found in the manual where it is supposed to go. To the adsorption canister in the emission control system. The problem is that all emission stuff has been removed from the car. No adsorbtion cannister, no catalytic converter, etc. Where does the vent tube go on cars without emission controls.
 
eejay - I don't think there is a vent tube on the early Spits (pre-cannister). I believe the tank was vented to the atmosphere through the fuel tank cap.

Usually when the cannister is removed, whoever does it will punch a small hole in the fuel cap rubber seal to provide some venting around the spring-loaded cap. They may also pull out the little 'cage' thingamabob that was installed in the fuel tank neck. The 'cage' has a spring loaded door that opens when you put the fillup nozzle into the tank, and when you take the nozzle out it closes.

The tank really doesn't need much venting when pumping gas out, the venting mechanisms were there to accomodate temperature changes that cause the tank volume to change (i.e. hot day, gas expands, need to vent) or to suck up some of the displaced air at the top of the tank when you fill up.

Leaving the vent line there and then putting the end in a plastic bag doesn't sound good to me. If you can get a cannister set up again, it would be a better solution. There is no real performance loss with a cannister (unless sometimes it gets plugged and causes problems) and its just a better all round solution, including environmentally.

I suppose you could test your theory by venting the tank to the atmosphere, just taking the plastic bag off the end of the hose and venting to a safe location, away from engine heat and spark, and see if that solves the problem.

If you want to test further, drive until you get the problem, and check if fuel is being pumped from the fuel pump to the carb bowl. If you're getting fuel pumped, then venting is not your problem.

A third test would be to leave everything the way it is, drive until you have the problem, and then just open the gas filler cap - see if that fixes anything.

Do you have a heat shield under the carb? Its possible you are getting some vapour lock. But at this timeof the year in Salem it should not be a problem,

You need gas, spark and compression to run. Given you don't have a problem with air flow and compression, that leaves spark and gas. You need to systematically rule things out.
 
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