Stall/crank No Start

[77Stanger]

1977 II 2.3 base model lowest of the low fantastic shape tho. Just put in a new battery and cables, new regulator, and had the carburetor professionally restored. After all this, still having the same problem. When the car is dead cold (sat for a day or two) it will start up maybe with an immediate stall, try it a couple of times and it will start running. maybe stall within 5 or 10 minutes. try it again and get it started and drive it around the block a little. after an hour or so try to start it to put it in the garage, if I'm lucky it'll start then stall just when i get it in. Hour or two later try to start it and only get a crank and no start for the rest of the day.
Anyone got any idea what it could be? After doing some research i think it must be the throttle position sensor but i have no idea what it looks like, where it is, or if the car even has one at all.
Please help if you know

Thanks

 

[jozsefsz]

There's no TPS on a '77 2.3.

Let's see, common causes of stalling -- vacuum leaks (including PCV valve & EGR valve), inoperative and improperly adjusted choke, timing is off, spark plugs fouled, weak spark (ignition module or coil), low compression, idle mixture is off (very possible since you say the carb was recently rebuilt), low idle speed, insufficient fuel (filter or pump), to name a few.

I'd start with looking for vacuum leaks, and replace the PCV valve if it's doubtful. Check the function of the EGR valve. Check timing. Check mixture (easy to do with a vacuum gauge). Pull your plugs and check their condition -- since it's stalling out and staying stalled, it's possible the mixture or choke problem are flooding your engine, and it doesn't start again until the plugs dry off. (note: if that's happening, change your oil sooner rather than later!)

Also, and I hate to say it, but if it's a square-butterfly, variable-venturi carb, you might be best off getting rid of it and swapping in a carb from an earlier model. Those are notoriously problematic carbs.

 

[77Stanger]

There's no TPS on a '77 2.3.

Let's see, common causes of stalling -- vacuum leaks (including PCV valve & EGR valve), inoperative and improperly adjusted choke, timing is off, spark plugs fouled, weak spark (ignition module or coil), low compression, idle mixture is off (very possible since you say the carb was recently rebuilt), low idle speed, insufficient fuel (filter or pump), to name a few.

I'd start with looking for vacuum leaks, and replace the PCV valve if it's doubtful. Check the function of the EGR valve. Check timing. Check mixture (easy to do with a vacuum gauge). Pull your plugs and check their condition -- since it's stalling out and staying stalled, it's possible the mixture or choke problem are flooding your engine, and it doesn't start again until the plugs dry off. (note: if that's happening, change your oil sooner rather than later!)

Also, and I hate to say it, but if it's a square-butterfly, variable-venturi carb, you might be best off getting rid of it and swapping in a carb from an earlier model. Those are notoriously problematic carbs.

Thanks for the reply. i have already done all of the tests for the coil, plugs, timing is perfect everything with the ignition is on point. New EGR valve, PCV valve is good. mixture is perfect could not have brought the carburetor to a better guy, its all he does, carburetor specialty, nobody better (actually the best) LITERALLY.
pretty much everything you mentioned i have already checked out and is spot on.
although i did recently notice that the car will not start and not start, but if i take off the air cleaner top cover, it will start immediately and not stall.
any idea on that? maybe air temperature sensor?

Thanks

 

[jozsefsz]

Did the gentleman who rebuilt your carb set the mixture with it on your car / running? If not, that would still need to be done. If so, well, perhaps that eliminates that, although as I mention the VV carbs were terrible out of the factory. Even if rebuilt 100% to spec, it's still an unpredictable carb, by design.

In any event, when you pull the air cleaner, you're leaning out the mixture. Definitely check if the choke is fully open when it's warm -- the cap may just need to be adjusted with the weather changing (I've never had luck with electric chokes myself). If I'm not mistaken the air temp sensor on these old cars just operates the little trap door in the stock air cleaner's snorkel. It's pretty easy to visually check that the flap is open when the car is warm. If it's not, it could definitely be contributing. But all signs point to a problem with your mixture.

Oh, and here's an after-thought... does the car still have its catalytic converters? Any thought to their condition? A plugged converter can also cause similar problems. A vacuum gauge can help you figure out if that's the case.

 

[77Stanger]

that is a very good thought about the catalytic converter, I've never really paid any mind to it and not sure what kind of condition it is truly in. now having said that does it make sense that sometimes when the car does stall, it does instantly after the air pump disengages, having to do something with the converter?

 

[jozsefsz]

The air pump is definitely related to the converter, though I don't think those things disengage, so not 100% sure what you're referring to. The easiest way to diagnose a clogged cat is with a vacuum gauge, basically if vacuum creeps down until it stalls, you might have some form of exhaust restriction. It's pretty much irreplaceable for tuning an old fashioned engine.