Engine backfire / car wont start
Thread Starter
Instructor
Joined: Dec 2001
Posts: 225
Likes: 0
From: League City TX
Engine backfire / car wont start
Ok I have beat myself up enough over this one so here I am again. As you know I'm a newbie at engine / carb stuff.
Ok the standard stuff:
1974 L-48
Edelbrock 1405 carb
Electric choke kit
The car was running fine before the electric choke. The manual choke was rigged 'open' and timed accordingly. The only problem was the first time it started after sitting overnight it requried a shot of gas into the carb.
After getting the electric cab on I had problems timing it. In my stupidity I have made it much worse instead of better. I had been playing with the dist timing and had it running before I started playing with the a/f screws and the idle screw and the choke settings.
Right now it sounds like it wants to start. Which is much better. It is like a fraction of a second away from starting. Just needs SOMETHING that I'm missing.
Tonight the engine itself backifired. Not the popping through the carb. This sounded like the heart of the engine and was as loud as a gunshot.
I am getting nervous as I dont want to cause damage but I want this fixed. So anyone in the canton ohio area that knows anything about engines/carbs etc please contact me. Otherwise please leave any advice you can offer.
Ok the standard stuff:
1974 L-48
Edelbrock 1405 carb
Electric choke kit
The car was running fine before the electric choke. The manual choke was rigged 'open' and timed accordingly. The only problem was the first time it started after sitting overnight it requried a shot of gas into the carb.
After getting the electric cab on I had problems timing it. In my stupidity I have made it much worse instead of better. I had been playing with the dist timing and had it running before I started playing with the a/f screws and the idle screw and the choke settings.
Right now it sounds like it wants to start. Which is much better. It is like a fraction of a second away from starting. Just needs SOMETHING that I'm missing.
Tonight the engine itself backifired. Not the popping through the carb. This sounded like the heart of the engine and was as loud as a gunshot.
I am getting nervous as I dont want to cause damage but I want this fixed. So anyone in the canton ohio area that knows anything about engines/carbs etc please contact me. Otherwise please leave any advice you can offer.
Drifting
Joined: Nov 2001
Posts: 1,469
Likes: 6
From: 68 427 4.11s Roadster
First set the timing and mixture screws while the engine is hot. You don't touch those for a cold engine.
It sounds like the timing is too retarded.
An electric choke is adjusted by turning it, the whole black case thing. It might not be hooked to the spring correctly so if it isn't working check that.
It also turns on with the ignition switch. It starts heating up whether or not the engine is running so after awile you don't have choke. And your getting pissed trying to adjust a thing that is shut off.
To adjust the choke turn the body until the choke plate is nearly closed when cold. This will take a little finangling to find the best spot. It probably won't happen today or tomarrow, once its found thats the spot though. You can only adjust for this when the engine is cold.
To tune the car while hot you have to adjust the timing AND the idle screw. If idle goes too high or low you readjust the idle screw, not the timing. If timing changed for some odd reason, readjust it. Rarely needed though. Mixture screws don't come into adjust timing or idle.
To start a carbed engine with choke.
This is whats happening. The choke controller ( manual, electric or bimetalic spring) closes the choke and moves a stepped cammed wieght. On these steps is where the fast idle screw is and how it adjusts the idle while cold. Very high idle, normal high idle, a bit lower and then no cold idle. Its like an assist. Without it you have one foot on the gas pedal working it too keep it from stalling. Your foot is the fast idle.
BUT-BUT for a choke to activate you must push the pedal down at least a minimal amount for that weight to move. If the weight don't move you don't have a fast idle and the engine starts and stalls out, idle is too low for engine temp.
Pushing the pedal down also squirts fuel into the carb. This isn't a 1 pump or 2 pumps but varies for every engine. Some like 3 others maybe one. You'll learn what your car likes.
So with the engine tuned for warm running and the choke set up for cold you push the pedal down, this sets the choke. You might give it a 2nd or 3rd pump. Start engine and after its running a short stab drops idle a bit, maybe.
If the engine is flooded and won't start hold the pedal to the floor and crank it. This will open every butterfly including the choke and clear the engine out for a retry. Mostly hot weather for a hot engine but if you got too aggressive with pumping the pedal then the engine is flooded even though its cold.
It sounds like the timing is too retarded.
An electric choke is adjusted by turning it, the whole black case thing. It might not be hooked to the spring correctly so if it isn't working check that.
It also turns on with the ignition switch. It starts heating up whether or not the engine is running so after awile you don't have choke. And your getting pissed trying to adjust a thing that is shut off.
To adjust the choke turn the body until the choke plate is nearly closed when cold. This will take a little finangling to find the best spot. It probably won't happen today or tomarrow, once its found thats the spot though. You can only adjust for this when the engine is cold.
To tune the car while hot you have to adjust the timing AND the idle screw. If idle goes too high or low you readjust the idle screw, not the timing. If timing changed for some odd reason, readjust it. Rarely needed though. Mixture screws don't come into adjust timing or idle.
To start a carbed engine with choke.
This is whats happening. The choke controller ( manual, electric or bimetalic spring) closes the choke and moves a stepped cammed wieght. On these steps is where the fast idle screw is and how it adjusts the idle while cold. Very high idle, normal high idle, a bit lower and then no cold idle. Its like an assist. Without it you have one foot on the gas pedal working it too keep it from stalling. Your foot is the fast idle.
BUT-BUT for a choke to activate you must push the pedal down at least a minimal amount for that weight to move. If the weight don't move you don't have a fast idle and the engine starts and stalls out, idle is too low for engine temp.
Pushing the pedal down also squirts fuel into the carb. This isn't a 1 pump or 2 pumps but varies for every engine. Some like 3 others maybe one. You'll learn what your car likes.
So with the engine tuned for warm running and the choke set up for cold you push the pedal down, this sets the choke. You might give it a 2nd or 3rd pump. Start engine and after its running a short stab drops idle a bit, maybe.
If the engine is flooded and won't start hold the pedal to the floor and crank it. This will open every butterfly including the choke and clear the engine out for a retry. Mostly hot weather for a hot engine but if you got too aggressive with pumping the pedal then the engine is flooded even though its cold.
Le Mans Master
Joined: Nov 2004
Posts: 6,128
Likes: 21
From: North Alabama
I know it sounds stupid but, hey, it happened once to me. It wanted to start, then a huge backfire and it blew rust flakes from the pipes against the wall. the Culprit? Me! The car was Out Of Gas! 
Thread Starter
Instructor
Joined: Dec 2001
Posts: 225
Likes: 0
From: League City TX
well oh well After everything I did, I decided to check the plugs. They were all carbon fouled so upon replacement and letting the battery charge overnight, the car started on the first shot without even giving it gas. All is good again. The floats have been measured 3 times, the a/f screws are correct and I will readjust the timing this weekend. Life is good again.
