I had an interesting morning. As a little background, I have a 76 with new intake and rebuilt carb last winter (Lars). It has ran fine up until this morning. Started it up drove for a bit and it started to run rough. After about 10 minutes of driving as I was going from a stop it really bogged even when giving it the gas then finally died. This is where it gets odd. I tried to restart it a few times and no turnover even after pumping then gas. After a few times of trying to start it when pumping the gas... nothing when turning the key. Just dead. I waited for 5 minutes and then the cycle repeated (wouldn’t turnover but starter was trying then completely dead). After the 3rd or 4th try I just stood on the gas while starting it and it finally fired up (immediately really high rpm) and limped home with a rough running car.

I know there are usually 3 culprits with rough running cars...vacuum, spark or carb but this one seems odd. Any ideas?

 

Sounds like it's flooding, maybe the needle/seat not sealing.

 

what is the easiest way to confirm this? I still struggle with understanding carbs.

 

If it was flooding there would be fuel all over the place and you'd smell it inside the car. Do you have a fuel pressure gauge installed? If not disconnect the fuel line from the pump to the carb and have someone crank the engine and check for fuel flow but before you have someone crank the engine pull the distributor car so the car can't fire. You could very easily have a plugged line or a fuel pump going bad.

 

Your post is confusing. No turn over while pumping the gas? Nothing while turning the key, just dead? Pumping the gas if the engine is not turning over will not start the engine. Pumping the gas and turning the key when you say its just dead doesn't help either. Sounds like you have a electrical problem.

 

The way it's written it sounds like the car loses power, then after 5 minutes it will crank again. I would think that it's a power issue at that point. Maybe a bad ground, failing battery, bad coil, worn cap and rotor. Start with spark and go from there. Check it like it needs a tune up

 

Sounds very similar to a situation I had. Was driving the car close to home. It just died. Coasted to a stop. Tried cranking it, with no luck. Waited, tried again, no luck. Called AAA and had a tow truck dispatched. Decided to give it one more try before the tow truck arrived and it fired up and I was able to get it home.
In my case, it was a bad coil. I believe the coil was going bad and would work when cold, but when the engine got up to temp, it would take a dump. After letting it cool a bit, it worked again. I installed a new coil and no further issues.

 

I am intrigued. Did your car run rough when you restarted it or was it just in a state of either running or dead? I have a new coil, plugs and wires I have had for a few years. Probably time to do it. But I am still wondering if it is a carb/fuel thing. Is there an easy way to see if the carb is flooding or starving for fuel? It would be nice to rule that out quickly.

 

I don't know why the car was running rough and stalled, but it's a pretty good bet that pumping the gas the way you did flooded the carb. If it should happen again, try just turning the key to restart w/o pumping the gas. If it doesn't fire up, press and hold the gas pedal to the floor and turn the key to re-start. Good luck in figuring out the problem.

 

well I only did that out of desperation once the car died and would not start again. It would try and crank for a bit but not start then completely dead. When it was cranking is when I was really pumping the gas. They car seems to start fine but just runs rough and won’t keep running.

 

It either ran or didn't. No spark, no run. But in my case, it would work sometimes. If you have another coil, its easy enough to swap it out and see if that does the trick. If not, then it's probably a fuel problem.

 

yeah and to be honest I am skeptical it is a spark/ignition issue but I just had the carb rebuilt by Lars so I struggle with it being a fuel problem. Maybe the fuel pump or it sucked up some debris

 

I changed the coil today and with no luck on it running better. I am going to keep going down the list of tune up items. Stand by.

 

You have a '76. You have a IGN Module. Original? Its under the rotor and old ones are prone to fail after a warm-up.

 

I put an octane booster in and a few gallons of premium. It started right up and was idling for for a few. I let it run for a bit (a few minutes) as it seemed to be running a lot better. I revved the engine a few times and when it came back to idling it was back to running really rough...barely not stalling. It would rev but then would go back to running really rough and about stalling when foot was off gas. Still at a loss.

so here is the list so far as to what I have done with no luck:

• Change coil
• Put in new gas/gas treatment

 

I had a weird issue last spring, i wonder if it happened to you. pull the distributor cap off and look inside at the button the rotor spins on. What happened to me wwas the distributor has a bushing in it that also had a c clip that retained the shaft. It held the shaft doen so that it wouldnt climb out the top. My bushing sheared and was not only eating up intothe cap but was changine the gap internal to the cap. Maybe your distributer itself is having issues.

I also had a distributor that the vacuum advance seized on back 30 years ago or so. If you advace is sticking its going to run okay until it sticks, then run rough at idle....Just ideas and another place to look

 

Using high octane fuel in your 9: 1 compression engine is a wast of money. Also using a octane booster don't help either. High compression needs octane, so unless you had 11:1 pistons or higher put in your engine don't use it. It actually will make you car run worse. If you suspect crud in your carb disassemble and clean it out. Did you change your fuel filter? what did it look like ? the filter will catch almost all crud coming to the carb if the filter is installed correctly. Fuel pressure come to mind, Have you checked the fuel pressure at the carb? Do you have any wet spots on the line coming from the tank? A crack in the line or rubber hose will cause the fuel pump to loose suction and not supply the fuel needed to keep the car running. As stated in other post above the distributor including the cap and rotor along with the shaft bushings should be looked at. I don't know anything about the electronic internal workings .

 

When was the last time you changed your fuel filter?

 

I had the carb completely rebuilt by Lars last spring. I have had the car for 4 years and never changed anything along the fuel supply...just a complete rebuild of the carb. I assume he changes the filter at that time. My next steps are Cap and rotor replacement...then maybe check fuel pressure?

 

The quadrajet has a fuel filter in the intake line housing, but there is probably a canister fuel filter between the fuel pump and the carb. Lars would not have changed that unless you took your car to him. If you sent the carb and he did his magic, then he just changed out the bronze or paper filter at the inlet.
Like someone mentioned...disconnect the coil wire to the distributor and make sure it is not flopping around where it might arc.
Disconnect the line at the carb and have someone crank the engine a few times while you let the gas shoot into a plastic one gal jug (milk jug) so you can see the strength of the flow and the volume. If the fuel sputters while coming out, work backwards from there....filter...fuel pump....clogged fuel line from rubber hose pieces that disintegrated inside and now clogging...and finally the fuel pickup and bladder in the tank.
I'd also pop the distributor cap off like mentioned and see if everything looks undamaged....you will know if it is.
Then go cylinder by cylinder and pull the spark plug wire off. While it is running rough. If no change in engine sound/vibration...that is either a bad wire or plug. If you find one, don't stop. Check them all. You might have more than one. Consider pulling all the spark plugs and inspect for black soot or wet with gas not firing.

Its fun diagnosing stuff.....don't get discouraged.
Its the price of the lesson so to speak.


Btw....have you contacted Lars yet? He is the man. Certainly will pinpoint the issue. He is not just a carb guy.
Good luck.