Coughing, backfiring ... *UPDATE*

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wheelman21

Mopar noob
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Ok so I have a 340 with an ultradyne cam, M1 intake and demon mighty demon carb. The car was running a bit rich, which I knew. It was tuned to run 100 octane. The previous owner didn't know that and was running 112. Just for the time being I was running 93 with booster and pulled some timing and stayed out of it to avoid detonation. I was headed uptown tonight and the car was running fine. I stopped at a store, came out and fired right up. About the time I went to pullout of the plaza it started coughing and sputtering. I got onto the street and to an intersection, it ran worse, and backfired like crazy. It sounded like someone was shooting a gun! The car stalled out and quit. I pushed it into a parking lot and tried to take care of it. I changed all 8 plugs and checked the dist cap. Idk what is going on. It is backfiring through the pipes and through the front two barrels. It started running the crap and doing all of this all of a sudden. Where do I start, what do I do now?
 
I agree. Sure sounds like it jumped time.
 
dustermaniac said:
Pull #1 plug and rotate to TDC, check rotor position to see if the timing is on the mark.
Click to expand...

He forgot part of this


dustermaniac said:
Pull #1 plug...............
Click to expand...

THEN STICK YOUR FINGER IN THE HOLE and bump the engine until you start to feel compression on your finger. This tells you that you are on the right "stroke." (Crank rotation.)

Then bump the engine until the timing marks are approximately where you have the timing set, 15, 20* BTC, etc

THEN...................


dustermaniac said:
.............check rotor position to see if the timing is on the mark.
Click to expand...

Check rotor position to see if it is actually pointing at no1 plug tower and the points just opened/ or the reluctor is close to the center of the pickup coil
 
67Dart273 said:
He forgot part of this




THEN STICK YOUR FINGER IN THE HOLE and bump the engine until you start to feel compression on your finger. This tells you that you are on the right "stroke." (Crank rotation.)

Then bump the engine until the timing marks are approximately where you have the timing set, 15, 20* BTC, etc

THEN...................




Check rotor position to see if it is actually pointing at no1 plug tower and the points just opened/ or the reluctor is close to the center of the pickup coil
Click to expand...


You are right. Sorry for the omission. I am tired. Been outside all day unfer the Duster replacing oil pump.
 
Ok fellas you lost me a little there. I'm somewhat new to timing these engines. I used to build VW engines, which were pretty easy to time without a light. I have a light and all just a little new to these particular engines.
 
The easiest way to do this is to remove the coil wire and then the #1 spark plug (front Drivers side) then using a helper to click the key over while you hold your finger over the spark plug hole at the #1 cylinder. You will feel the pressure push against your finger as the engine is being rolled around and "push" your finger out of the hole. At this point you can use a small screwdriver and insert it into the spark plug hole and you should feel the top of the piston just inside the hole. this will be very close to Top Dead Center on the compression stroke. Then, remove the distributor cap and take note of where the rotor is pointing in relation to where the spark plug wires are located on the cap as if the cap was clamped down. The rotor should be pointing at the wire that goes to the #1 spark plug. if it is not then the timing chain has probably jumped a tooth. be very careful when you click the engine over not to go past the top dead center on the compression stroke.
 
Ok I figured that's what you meant. I used to do the same with the VW engines. He just started throwing around some terms that threw me off. If this did jump a tooth, am I going to have to take stuff apart, or just reset the timing?
 
There is no way that timing "just moves" unless the distributor clamp is loose. If it moved, you need a timing chain/ cam drive
 
pull valve covers off and look for bend pushrods...or rocker arm adjuster broke..

or if stock rockers...see if you pushed a pushrod thru a rocker ..
 
Anyone think this could be a carb issue? I'll check the timing and make sure it didn't jump somehow on the chain. The clamp on the dist was tight. I'm just curious if it could be a carb tuning issue, like a cloggled jet.
 
wheelman21 said:
Anyone think this could be a carb issue? I'll check the timing and make sure it didn't jump somehow on the chain. The clamp on the dist was tight. I'm just curious if it could be a carb tuning issue, like a cloggled jet.
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Just to be clear, a "clogged jet" is not a "tuning issue," but yeah, you may have ingested a bunch of crap into the carb. Certainly worth checking out
 
67Dart273 said:
Just to be clear, a "clogged jet" is not a "tuning issue," but yeah, you may have ingested a bunch of crap into the carb. Certainly worth checking out
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Yea by "tuning issue" I meant something out of whack. I pulled bot jet sets and cleaned them out. They didn't look to be plugged.
 
Ok So I check timing, seems to be ok. No obviously bent rods or rocker issues on bank 1. I got it running again. It's not missing or coughing too bad. It is still idling rough and every once and a while backfiring. I am pretty sure it is because it is running so rich. It just reeks of fuel. It's not banging or knocking like something on the rotating assembly is broken. I replaced the plug wires just in case that was part of the problem. Any ideas on how to lean out a mighty demon?
 
Last night after new wires and some tweaking I got it running, albeit pretty rough. I put a timing light on it, and reset the timing. I timed to 19 initial and around 32+or- total. It cut out, and I couldn't get it back. I put a new dist cap on, and tried to start it. It will only run while I'm on the starter. I let off, and it shuts off. It will fire with the starter engaged but then shuts off. I'm going crazy trying to get this thing running. HELP!
 
Go back to the basics. Check your wires for orientation, it's easy to mix them up. 18436572 clockwise around the cap. Passenger side of block is even 2468 from front to back, drivers side is odd 1357 front to back. Double check your air gap on the reluctor, should be .008 checked with a non metallic feeler gauge.

If the cylinders aren't firing properly and not burning the gas you could smell raw fuel. It could be running rich as well.

What are your cam specs? Not that it would help me much, but might shed some light to the more knowledgeable here.

Try a little less initial. I have my initial at 16* with 38* all in by 2500 rpm.

Are you running a ballast resistor? Probably not your problem but you can bypass it briefly to see if there is a difference.

What about your coil, do you have a spare to throw at it to see if that changes anything?
 
"Running on the starter" could be a bad ballast. Check and see if you have power to the coil/ ballast with the key in the "run" position.

Have you checked the spark? You want to do this using the KEY to crank, because that gives you the best "cranking" spark. (Cranking with the key in "run" and jumpering the starter relay does NOT bypass the ballast resistor, gives you a weaker spark)


You'll either need two people, or a way to "rig" a test gap for the coil wire.

If the spark at the coil wire looks OK, Look at the plugs. Are they wet/ fuel fouled?
 
wheelman21 said:
Last night after new wires and some tweaking I got it running, albeit pretty rough. I put a timing light on it, and reset the timing. I timed to 19 initial and around 32+or- total. It cut out, and I couldn't get it back. I put a new dist cap on, and tried to start it. It will only run while I'm on the starter. I let off, and it shuts off. It will fire with the starter engaged but then shuts off. I'm going crazy trying to get this thing running. HELP!
Click to expand...

It would be the ballast resistor:
P4120808resistor.jpg

or this one:
ballast-resistor-5206436.jpg
 
#1 ballast resistor.
#2 check to see if you have voltage at the + side of the coil when the key is on run.
#3 ecm took a crap.
#4 coil took a crap.
#5 timing chain jumped.
What ignition and what is the condition of the motor?
If points check #1,2,5 above, then verify the condition of the condinser in the distributor.
 
I check the ballast and don't think it's them. I checked timing, and it's good, checked plug wires and replaced cap. I tried switching out ignition controller and nothing. I talked to Don at FBO and he was confident that it's a carb issue and that the carb is flooding out which explains the fouled out plugs and why it reeks of fuel even if I haven't touched the pedal. It also explains why the other night it was flooded when I went to start it, even thought I hadn't touched it. I'm going to clean the float bowls, air bleeders, and replace the needle and seats with bottom feeders. Hopefully with everything cleaned out we'll be back in business.
 
How did you check the ballast resistor?
Put a small wire from 1 side of the ballast to the other and see if it stays running. If it does, then it is bad.
 
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