79 dodge aspen 318 w/ constant backfire
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79 dodge aspen 318 w/ constant backfire
Hi im a rookie at this and this was my first rebuild. Well i rebuilt my 318 and have i back together but it is constantly backfiring, iv messed w/ the carb, cleaned all plugs, checked the wires, and there is no leaks in the exhaust. It starts to pop when under pressure and when idling it also will die when left too long.
Your help will be really appreciated.
Thanks
Your help will be really appreciated.
Thanks
Mopar Lover
Joined: Nov 2007
Posts: 2,424
Likes: 248
First, define what you mean by backfireing
Does it pop back through the carb, or
crackle and pop out the exhaust when you "let off" the throttle?
I'm assuming it pops back
Under what conditions does it do this?
alll the time?
when cruising?
when under power?
when under heavy power?
at high rpm, medium, all ranges?
A rythmatic popping, like a dead cylinder, can be caused by a flat cam load on an exhaust valve, and of course sticking valves, broken springs, burned valves, etc
(Run a compression check)
Are you ABSOLUTELY sure that
the plug wires are in the right order? (Very easy to switch 7-8-
The plug wires are good? Check them with an ohmeter
Is the distributer cap new, clean, and dry? Pull the cap and look for "carbon tracks" between two connections
Can you get a smooth idle? Do the idle mixture screws have a noticeable effect?
Try this: Get a small screwdriver, or a test light. Ground the screwdriver with a wire/ clip lead to the block. Pull the boots loose off the distributor cap. With the engine at the smoothest idle you can get, short out the spark at each cap tower one at a time. Watch a tach if possible. EACH CYLINDER should drop the idle about the same amount of RPM, and the engine should "sound" about the same on each. CONGRATULATIONS!! You've just performed a "cylinder balance test" with no special equipment.
If any one or two cylinders doesn't "drop" the same amount, it indicates a problem in that cylinder
If two cylinders that are physically adjacent on the block are weak, you might have a head gasket leak between those two cylinders
How did the plugs look, any evidence of something like antifreeze leaking into the cylinder?
Does it pop back through the carb, or
crackle and pop out the exhaust when you "let off" the throttle?
I'm assuming it pops back
Under what conditions does it do this?
alll the time?
when cruising?
when under power?
when under heavy power?
at high rpm, medium, all ranges?
A rythmatic popping, like a dead cylinder, can be caused by a flat cam load on an exhaust valve, and of course sticking valves, broken springs, burned valves, etc
(Run a compression check)
Are you ABSOLUTELY sure that
the plug wires are in the right order? (Very easy to switch 7-8-
The plug wires are good? Check them with an ohmeter
Is the distributer cap new, clean, and dry? Pull the cap and look for "carbon tracks" between two connections
Can you get a smooth idle? Do the idle mixture screws have a noticeable effect?
Try this: Get a small screwdriver, or a test light. Ground the screwdriver with a wire/ clip lead to the block. Pull the boots loose off the distributor cap. With the engine at the smoothest idle you can get, short out the spark at each cap tower one at a time. Watch a tach if possible. EACH CYLINDER should drop the idle about the same amount of RPM, and the engine should "sound" about the same on each. CONGRATULATIONS!! You've just performed a "cylinder balance test" with no special equipment.
If any one or two cylinders doesn't "drop" the same amount, it indicates a problem in that cylinder
If two cylinders that are physically adjacent on the block are weak, you might have a head gasket leak between those two cylinders
How did the plugs look, any evidence of something like antifreeze leaking into the cylinder?
Guest
Posts: n/a
It goes out the exhaust and I know there is some popping from not having pipes out the back but thats not all. It pops some when in idle and it has that rhythmic pop when accelerating. Normally its really pretty quite but when it accelerates and I let off the gas it'll really backfire load. But what really bothers me is when I let of the gas and let it idle it will die pretty fast.
Mopar Lover
Joined: Nov 2007
Posts: 2,424
Likes: 248
A rythmic pop sounds more like a weak cylinder. Read my post, take a compression test, and try the cylinder balance test.
You may have more than one problem, namely something in the idle circuit of the carb. Do the idle screws have good effect?
You may have more than one problem, namely something in the idle circuit of the carb. Do the idle screws have good effect?
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