Engine starts, misses and stops... ?

[Rock&Roll Firebird]

Hello guys, another riddle. About two weeks ago I took my Bird out. On a highway the engine started to miss exactly in a way when a fuel would be running out. As my fuel gauge did not work at that time, I pulled the car over, added about 10 liters of gas started normaly and finished the remaining 10 kilometres of the trip. On a way back, after about 5 kilometres, the car started exactly the same bahaviour. After the engine startup it was missing a lot as if insuficient gas would be pushed into the carburetor. I called the AAA and the car was moved on a trailer into my garage.

So I figured the gas tank, filters and lines need to be checked, exchanged and cleaned. And thats exactly what I did this week. Unfortunately the problem presists. Just a note - the gas pedal does push a stream of gas into the caruretor and intake. I created a short video - not sure if it is of any help (and my mobile rotated it in a wrong way...). Anyway, if you could check it here:

https://youtu.be/EXm_H0td_N8

and let me know where to start digging (distributor or a coil maybe), I would be very gratefull.

[Joe Johnston]

4 things come to mind:

if you are using points and condenser, maybe the condenser is failing when warmed up. When this happens the engine will run OK cold but not hot. If using Petronix it may be failing.

Coil may be failing when it gets warmed up

Vacuum advance may not be working

Carb power valve not working (but I doubt it from your description)

[Rock&Roll Firebird]

Just need to add, that the video and the engine behavior today was with a cold engine.

[jopizz]

It does seem that it's being starved of gas. You could have some dirt in the carburetor. The accelerator pump in the carburetor may be bad. As mentioned I would check the vacuum advance also. I can't tell by the video whether your choke is working properly.

John

[Rock&Roll Firebird]

It does seem that it's being starved of gas. You could have some dirt in the carburetor. The accelerator pump in the carburetor may be bad. As mentioned I would check the vacuum advance also. I can't tell by the video whether your choke is working properly.

John

The accelator pump works properly I guess - as it sprays the gas into the intake when the gas is iniciated. The choke was closed on the cold engine and the very same behavior was when the engine was hot.

[Sherman]

Hello, how about a faulty fuel pump or clogged filter that is in some of the older "glass style" fuel pumps?

[Rock&Roll Firebird]

Hello, how about a faulty fuel pump or clogged filter that is in some of the older "glass style" fuel pumps?

The fuel pressure from the tank should be OK as I have an. el. pump installed on the tank that seems to work fine. Also I installed a transparrent/plastic fuel filter near the carb to see the flow of the gas to the carb and everything looks fine there.

[Guest]

If you just installed the electric fuel pump, check the fuel pressure. If it is more than 6 or 7 psi that is too high and will flood the carb and load up the engine or foul the plugs. Most of the mechanical fuel pumps only provided 3-5 psi fuel pressure.

[Rock&Roll Firebird]

So, the story continues. Today before I cranked the engine I removed the carburetor cover to check the fuel level in the body. Both chambers seemed filled with fuel at appropriate level so I guess there should be no problem in feeding the carburetor with gas.

Also I wanted to check the choke and it's role in the present situation. I covered the carb and cranked the engine. The engine was idling for about 4 minutes and got into working temperature. During that time the 'missing' symptome was still there. The only way to keep the engine from stopping was to gently keep the choke from standard and full opening. When I released the choke to open after about 4 minutes of engine idling, the engine stopped. This first part is recorded in the first video here:

https://youtu.be/CvSan8LWtw8

Wasn't exactly sure what that supposed to mean but decided to crank the warm engine again and give it a bit of load. That's exatly what I did - pushed the acceletator hard for several times. And suddenly, everything started to work just fine - no more 'missing' and the engine ran smoothly with the choke fully openned. I let I run for about 5 minutes then stopped the engine, cranked again and let it run again without any problem. Recorded this state into video here:

https://youtu.be/D4pFbU8LE3E

What I think about this situation, it seems that the problem is neither electrical related nor vacuum advance related. Seems to me like something that was restricting the fuel flow in the carb was released with the sudden 'load'. The question is - is it gone from the carb? And if not - how to check that. I will be testing the engine on the yard for now before I take the Bird to the streets.

Any of your opinions or suggestions what else should be checked are welcome.

[jopizz]

I would like to say your problems are over but from experience whatever caused it to run rough will most likely come back. It's one of the reasons I ditched the Ford carburetor and went with an Edelbrock. Even with a new tank, new lines, new fuel pump, new filter and rebuilt carburetor I still couldn't get mine to run smooth for more than a couple days. Then I would have to take it apart and clean it out even though it looked perfectly clean. If I took the idle mixture screws out and shot carburetor cleaner into the holes it would run fine for a couple of days and then it would start running rough again. I chalked it up to something in the modern fuels and left it at that.

John

[Dan Leavens]

John good advice. As the saying goes 10 Holley carbs= 1 good operating carb. I agree Edelbrock minimum 640 cfm.

[Rock&Roll Firebird]

I would like to say your problems are over but from experience whatever caused it to run rough will most likely come back. It's one of the reasons I ditched the Ford carburetor and went with an Edelbrock. Even with a new tank, new lines, new fuel pump, new filter and rebuilt carburetor I still couldn't get mine to run smooth for more than a couple days. Then I would have to take it apart and clean it out even though it looked perfectly clean. If I took the idle mixture screws out and shot carburetor cleaner into the holes it would run fine for a couple of days and then it would start running rough again. I chalked it up to something in the modern fuels and left it at that.

John

Thank you John. That being said, I will order the Edelbrock 1406 to save troubles in the future. Is it difficult to install the new carb and should I get any additional parts that may be needed with it?

[jopizz]

The Edelbrock carb is very simple to install. The hardest part is finding 12V for the electric choke. If you have power windows you can hook it up to the relay on the firewall. If not you will need to run a wire to a switched 12V source. You may need to adjust the accelerator rod slightly. I think I had to turn mine out few turns to make it longer. Just bolt it on, connect the vacuum advance to the full vacuum port, connect the fuel line, the accelerator rod, the accelerator linkage spring, the choke, block off the unused vacuum ports and you are good to go. It comes preset as far as the idle mixture screws go but they usually need a small adjustment as do the idle speed adjustments. I had to put a large rubber o ring about 1/8" thick between the air horn and the air cleaner so it fit correctly. It's an easy upgrade and well worth it.

John

[Rock&Roll Firebird]

The Edelbrock carb is very simple to install. The hardest part is finding 12V for the electric choke. If you have power windows you can hook it up to the relay on the firewall. If not you will need to run a wire to a switched 12V source. You may need to adjust the accelerator rod slightly. I think I had to turn mine out few turns to make it longer. Just bolt it on, connect the vacuum advance to the full vacuum port, connect the fuel line, the accelerator rod, the accelerator linkage spring, the choke, block off the unused vacuum ports and you are good to go. It comes preset as far as the idle mixture screws go but they usually need a small adjustment as do the idle speed adjustments. I had to put a large rubber o ring about 1/8" thick between the air horn and the air cleaner so it fit correctly. It's an easy upgrade and well worth it.

John

Thank you John, seems I should be able to do this with your helpfull description. I'll get back to report when the new carb is up and running.

[Tbird1044]

It always seems to come up that the fuel inlet on the Edelbrock is on the right rear of the carburetor, behind the choke, vs. being on the front of the carb like the Autolite. Not a major deal, but it is probably the biggest modification needed. You'll either need to bend some tubing or run some rubber tubing to the inlet.
Nyles