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General Tech Backfiring

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Further on this matter, I installed the Pertronix and cleaned the plugs on the car and took for another test drive. Started fine, ran fine for a while, then same problem occurred. Car would backfire, loss of power, occasional total miss. Barely made it home and into garage. I agree with most of you that this is ignition.
Other observations: very low slow idle speed (300-400), ran better with choke, even with choke fully on car only probably made 600 rpm.
Comments are always appreciated. Thankyou.
 
Dashpots full? I had similar symptoms until forum members told me to put a heavier oil in my dashpots.
 
Thinking this is still an ignition problem; is there something in ignition that could change as engine gets hotter? Seems to run fine at first, then starts all the missing, backfiring etc. If cap was faulty could that get worse as things heated up?
 
Have you checked your timing?, what about the old points, cleaned and regaped? Is the correct firing order happening? Vacuum advance working?
Start with the basics and go from there!
 
Crisis said:
Thinking this is still an ignition problem; is there something in ignition that could change as engine gets hotter?
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Coil failures can be brought on by heat. Less common but I seem to recall a condenser can fail with heat. Either can be a partial failure resulting in a miss. For that matter, I suppose a plug could fail with heat though I have not experienced that.

I didn't go back & read if this was already suggested -- but when the miss is occurring you might watch the engine running in a darkened garage -- looking for stray sparks.
 
Thanks guys. Replaced the points and condenser with Pertronix ignitor (and what appeared to be a bad ground wire going to distributor), but I did this as a solution to the problem that still exists. Needless to say, I don't like driving this car as it is rather embarrassing when power dies and I can't leave a stop sign or it backfires and scares the pants off everyone.
 
Check the air valve diaphragm. Some but not all of your symptoms sound like it would be worth having a look at.
Be sure to read the procedure so that you'll replace it oriented correctly.
 
Good reference except I think you (like me) had forgotten that the subject vehicle is a '65 E-Type with triple SUs.

I'm afraid advice here may be somewhat limited.
 
Geo Hahn said:
Good reference except I think you (like me) had forgotten that the subject vehicle is a '65 E-Type with triple SUs.

I'm afraid advice here may be somewhat limited.
Click to expand...

There's the problem...we need to get him a Triumph!
 
Hi Tom,
You're right I haven't replaced the cap or rotor, only the points/condenser for electronic. Of course I guess that means the rotor could still be bad; hadn't thought of that. And the cap looks fine but I guess that doesn't mean it is. I'll try changing those out. Thanks.
 
There seems to be a general opinion that the problem is ignition-related, as though backfires in the exhaust system were ignition-related.
My experience suggests that over-rich mixtures can lead to unburnt fuel in the exhaust system which may detonate, particularly on the overrun and more particularly if there's a leak in the system allowing air in.

There's no mention of any attention being paid to carburation. If, after the symptoms develop, it idles better with more choke, and the symptoms develop after a little running, I'd be checking for sticking dashpot pistons were it my car. Particularly if it's had modern gas sitting in it for a year!
 
Hi Chris, the reason that I would consider the cap is that over many years and a wide variety of cars, trucks, farm tractors and other engines I have encountered a similar problem. For some reason I believe to have been from condensation in the cap after sitting over the winter, after running fine in the Fall, when starting in the spring they would have a serious miss and or backfiring from the spark tracking between posts in the cap. Sometimes to the point the engine would not even start.
 
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