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AQ120B stops running

jjlutzel

Member
"The engine will start, run fi

"The engine will start, run fine for a period of time, over an hour at idle, less than that at speed, then it rumbles for a few seconds and shuts down. After a few minutes it will turn over, backfire, turn over some more, then restart and do it all over again.
The timing is set about 12 degrees off TDC at a fast idle (1200 RPM), and about 30 degrees at speed (3000 RPM).
It has a new timing belt, tensioner, timing wheels (gears), new points, plugs, ignition coil. I haven't changed the spark plug wires.
I cleaned all the electrical contacts in case it was an electrical problem. I installed a shunt with a toggle switch around the ignition switch, but that didn't help.
My thinking now is a fuel problem.
Any ideas?"
 
"You might have a defective co

"You might have a defective condenser. With these symtoms I'd change out the condenser first and see if that helps. Be sure the spot where the ground cable attaches to the engine block is clean and britened. You might check for a clogged gas tank vent. If the vent is blocked, a vacuum can form a vacuum in the tank as the fuel goes down. If that happens again, loosen the gas cap. If there is a "woosh" of air and/or it starts running OK again, you have a clogged fuel vent"
 
Eddie;

I forgot to add the


Eddie;

I forgot to add the condenser to the list of parts that were changed. I'll follow up on your suggestion about a clogged fuel tank vent. I never thought of that.

Thanks
 
"Put back in the old condenser

"Put back in the old condenser, if you still have it around or get another new condenser. Condensers are notorious among ignition components for being bad, brand new right out of the box."
 
"Eddie;

The old condenser


"Eddie;

The old condenser was in pretty bad shape and was thrown away. But they are cheap enough to try another one, or I could install an electronic ignition as has been suggested at another time on this forum."
 
"Hi, El.

Your message isn&#


"Hi, El.

Your message isn't posted here, but I got your e-mail. Thanks.

I removed the ignition switch and cleaned the contacts. I also installed a wire from battery + to the coil + through a fuse and a toggle switch and let the engine run until it stalled. Then I threw the switch, but nothing happened. It would not start.

Today I removed the fuel line from the tank to the fuel pump hoping it would be clogged. Nope ... it's wide open.

There is gas at the input to the carb from the pump, the throttle disc opens and closes as I move the throttle and gas comes out of the nozzle, but I don't know the flow rate or whether it is enough to support the engine.

Tomorrow I'll try Eddie's idea about a clogged tank vent.

Any other ideas are welcome."
 
"Joe, you may want to try some

"Joe, you may want to try something else as well. Remove the fuel tank hose from the fuel pump and connect a hose from a jerrycan full of fresh gas, then start the engine. If the problem persists, the fuel vent or fuel lines, anti-syphon valve, etc is not the problem."
 
"El;

I'll try that. It


"El;

I'll try that. It will also tell me if I have water in the gas (which I doubt, but who knows)

Thanks."
 
"Yes, the condenser is a relet

"Yes, the condenser is a reletively inexpensive item, so it a case like this get another new one."
 
"It would probably be cheaper

"It would probably be cheaper in the long run to install now a Pertronix electronic ignition kit.
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"Today the engine started and

"Today the engine started and ran fine for a while. When it began to run rough I threw the switch I installed for the ignition switch by-pass and this time the engine picked right up again and ran fine for about an hour and a half until I shut it off. I'll put in a new ignition switch.

All this is while it is at the dock. I have not taken it into the open water yet, so I don't know if it will run under a load.

El, I think it is probably time for the electronic ignition. I was holding off because I was afraid that the engine had come to its final resting place and I did not want to put more money into it. But now it looks like maybe it still has life.

The only thing that still concerns me is that the RPM drifts, which could indicate a fuel problem. If it does not run out in the Bay I'll try the test you suggested with the jerry can of gas."
 
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