So, Went to start my 74 Duster , and it would not fire. When I went to turn the key off it seemed to start a little. Tried again and as I turned the key off it Popped-backfired. What do you guys think?
Backfire-after turning key off
- Thread starter TF360
- Start date
-
Bad ballast resistor.
v8fish
Well-Known Member
What Rusty said
KitCarlson
Well-Known Member
Nope. The ballast is bypassed when cranking, so if ballast is bad it will try to start, but die in run.
My guess is a short on the coil -, or bad transistor in ECM. When you turn it off, you get a spark, but it is not in time with engine.
The other possibility is pickup related, faulty, gap too wide, or connector issue.
My guess is a short on the coil -, or bad transistor in ECM. When you turn it off, you get a spark, but it is not in time with engine.
The other possibility is pickup related, faulty, gap too wide, or connector issue.
This^^^^
Or faulty ignition switch.
Or faulty ignition switch.
yellow rose
Overnight Sensation
I actually had a bad rotor do the exact same thing. It would let the brass blade on the rotor spin away from the post while cranking, and as soon as you let off the key the little brass piece would get back in place and make it act like it wanted to start.
Bulldozer
free ice cream sandwiches
Take the ignition box off and scrape the mounting points down to bare metal. Make sure all your grounds are good. If that doesn't work, try another ignition box.
TrailBeast
AKA Mopars4us on Youtube
Probably just the extra drag from the trans depending on how much it came down.
TrailBeast
AKA Mopars4us on Youtube
WHAT???
Where do you come up with the weird stuff you do.?
I have had them come off before and the person that owned the car was totally stumped on why it wouldn't run.
It's one of those things your eyes just kind of move to involuntarily so I saw it as soon as I took the cap off.
TrailBeast
AKA Mopars4us on Youtube
Not if the fault is no power on the start side.
The ignition switch can be bad on the start side and fire a spark only when you let go of the key, but most engines I have had fire up at that point anyway just because they are already spinning.
They don't usually backfire though as I would call a backfire.
KitCarlson
Well-Known Member
Are you aware of fast idle, as part of the choke function? Cold gear oil loads the engine a bit. Had a bug that would drive in neutral at -10F.
KitCarlson
Well-Known Member
There would have to be two faults, IGN1, and IGN2. But, it backfired, that happens if it has even cranked with fuel present, coil energized, then key off. If the ECM is not triggered, shorted, or coil- grounded, key off makes a spark. With V8, high probability it will pop on some cylinder, but not in correct time.Not if the fault is no power on the start side.
The ignition switch can be bad on the start side and fire a spark only when you let go of the key, but most engines I have had fire up at that point anyway just because they are already spinning.
They don't usually backfire though as I would call a backfire.
TrailBeast
AKA Mopars4us on Youtube
This could just be a tuning thing.
One thing just in case though, is I noticed one day recently while chasing an erratic idle that wouldn't come down all the way.
(It bugs the crap out of me when things act different every time)
Anyway, I found that the linkage on the passengers side of the carb that blocks the secondaries closed was dragging on the it's corresponding component cause the idle to stop at different places and the only way I could get it to idle down to it's normal idle was to blip the throttle.
Giving just a slight bend to the linkage part solved that and the idle speed is rock solid the same every time now.
This is the the piece I had to bend up a little to get it to idle down reliably.
TrailBeast
AKA Mopars4us on Youtube
Or if it has no ignition power in start but does when you let go of the key to run but it doesn't continue to run.
But this way it doesn't backfire, but just fires a cylinder but doesn't start.
Some call that a backfire, but I don't consider it one.
KitCarlson
Well-Known Member
It is a backfire when goes out the exhaust, the wife hears it, and the chickens run back to their pen. 
I go with TF360, he said backfire.
I go with TF360, he said backfire.
yellow rose
Overnight Sensation
WHAT???
Where do you come up with the weird stuff you do.?
I have had them come off before and the person that owned the car was totally stumped on why it wouldn't run.
It's one of those things your eyes just kind of move to involuntarily so I saw it as soon as I took the cap off.
If it's weird, absurd, ridiculous, outrageous or unheard of, most likely it's happened to me.
I know, because every time something goes wrong and I call the manufacturer they always say "you are the only who has ever called us said this to us".
So yup, I must be the only one. At least that's what they tell me.
Hell, if I told you my drinking stories you'd think I was a fibber!
I didn't mention this, but I put a new coil on and it fired up and ran. Drove it for a while and parked it. I went to start it a week later and Back to no start (turns over) and tries to fire right before key is in off position.
KitCarlson
Well-Known Member
Snap a picture of coil connections. The coil - should have only one connection from ECM, unless you have a tach. Removing tach wire, and try starting, is good test.
When cranking and again in run, test voltage at coil +, to ground.
When cranking and again in run, test voltage at coil +, to ground.
-
