1980 Datsun 310 intermittent stalling

First thing you need to do is determine if this is a spark or a fuel issue. You can connect a mechanical fuel pressure gauge and lay it on the windshield then go for a drive to see what the fuel pressure is when the problem happens. You can also keep your timing light in the car and hook it up real quick when it conks out to see if you still have spark (just watch the flashes).

Steve B.

I would suspect the vent on the gas tank has gotten blocked. The test is to open the gas cap next time it happens and see if it is instantly fixed.

I don't know about yours, but lots of 80's carb vehicles had a charcoal filter for a gas tank and carb float bowl vent. There is a $2.00 air filter on the bottom that is supposed to get changed now and then. The first one is a bugger do dig out, but after that the new ones just tuck in.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - G> Hi everyone,

This was a long time ago so I don't remember all the details. I had a carbureted Honda that did the same thing. There was a vacuum leak. I think a hose or cap had popped off. This caused icing at the carburetor. I capped the leak and it ran good for as long as I had the car. It must have been the hot air diverter that was not working.

The vacuum leak and the charcoal canister are good ideas. You didn't mention if you replaced the fuel filter. I had a Toyota truck doing this, and it was the filter.

Thanks to everyone for your help. I can't seem to make the problem happen now that I'm ready to study what's going on when it happens... (Murphy's Law). The fuel filter is about 3500 miles old, but I'll try a new one, they're pretty inexpensive. Also I would note that in the carb float-bowl level sight-glass, the level is often above the "correct level" mark (about 2-3mm above) but then other times, the level is normal. Is it normal for the gas in the carb to be above the "correct level" mark at any time? Also, when is it best to inspect the gas level: when the engine is running or not running? Thanks so much for the help.

-Andy

It sounds like your observation about the problem occurring every 45 miles was incorrect.

I think you are now more on the right track. When an engine dies because it is getting too much gas (rich) it usually involves a good bit of sputtering and chugging as you described. If an engine dies because it gets too little gas (lean) it is usually happens pretty fast almost as if the ignition was turned off. The fact that it has to sit for a while to restart also suggests a rich condition. If it happens again check for black smoke out the exhaust (either when it dies or as you get it restarted). Any dark smoke out the exhaust will pretty much confirm the problem is due to getting too much gas.

The level of the gas in the carb float bowl should not change. It should stay the same whether the car is running or stopped. You may see some small variation in the level if the car is not sitting on flat ground. If you do have an intermittent problem with the float, it could be a mechanical problem with the float assembly itself or it could be due to dirt or gum in the gas keeping the float valve from seating properly. You also might have problem with something getting too hot. If either the carb or air intake or gas lines get too hot it could be the cause. You also need to make sure the float chamber is venting as it was designed to.

-jim

If the needle valve is restricted, then the float level will drop any time the car is pushed past a particular fuel consumption level. Push the accelerator past 40% for 20 seconds and the car will literally run out of gas. Let it sit for 10-15 seconds and the float will refill and everything will run like nothing happened.

Maybe, but seems very unlikely. Absolutely nothing in his description fits that scenario. Of course one never knows. It's always possible that everything that the OP said happened could have been remembered incorrectly. The OP could have said it cuts out whenever he tries to accelerate up a hill, but he didn't say that so I'm assuming it doesn't.

So what does that have to do with the description the OP gave?

-jim

You have a carb issue. It sounds to me like it is periodically running too rich. I'd check the float and the needle valve and make sure everything is completely clean. I'd also check for vacuum leaks, but you may be getting ready to do a carb rebuild if you have a gasket leak going on somewhere.

My guess is that the needle valve is sticking open... the carb fills up, the engine stalls. You have to wait a few minutes for some fuel to evaporate before it will start again.

--scott