Yoda4561
03-23-2016, 08:05 PM
After enjoying over a year of excellent reliability I had a fun week of chasing down some ignition gremlins (first suspected points and coil, discovered bad diaphram on the vac advance the day after, found a short on the wire from the starter to the coil a few days after that, then a loose battery cable (the one I didn't touch at all when I was working on the electrical stuff) I got the firebird running great for all of half a day.
Today the engine started softly cutting out about 20 minutes after driving it around and stalled out once at a stoplight, popped the hood open after pulling into a parking lot and notice no fuel at all in the clear filter between the fuel pump and carburetor. Shut it down and fuel started slowly moving back into the filter but I couldn't tell from what direction. Restarting it immediately was no problem after it stalled, no problems restarting it after it sat for 30 minutes either, one or two turns of the starter and it started right up. The engine continued to miss occasionally on the short ride back home though. Rechecked timing and it was right where I set it after the ignition work, 12 btdc without the vac advance hooked up. Vac advance is hooked up to full manifold vacuum
Nothing much has changed on the car in the last year that would cause me to suspect vapor lock as it was driven regularly on 100 degree days last summer and it was rock solid reliable. It uses a stock style mechanical pump with the oe charcoal canister and vapor return line. Fuel lines are all in the same place they were when it ran fine all last summer, engine doesn't seem to be overheating. I did switch from a 160 to a 195 Tstat but it was fine after I did that for months, and some weeks during this winter in FL were in the 90's. On the other hand the last few times it's had this issue it ran fine in the mornings when the motor was cold and started acting up after being driven a while.
The fuel pump I suspect had a bad checkvalve when I got it, as the fuel filter would empty within a few seconds to a few minutes of shutting the engine off and took a little while to fill it back up after starting. Engine always started quickly and it didn't cause drivability problems so I just left it alone. A new pump is on the way now and I'll be replacing it when it gets here in a few days but in the meantime is there any acid test to determine if it's vapor lock and not just a flakey pump? Maybe just a case of a bad tank of gas? fuel sock clogged? (it's probably never been touched since the car left GM) If I'm overlooking any easy or common issues/fixes I'd appreciate some advice as this is my daily driver/only car.
Today the engine started softly cutting out about 20 minutes after driving it around and stalled out once at a stoplight, popped the hood open after pulling into a parking lot and notice no fuel at all in the clear filter between the fuel pump and carburetor. Shut it down and fuel started slowly moving back into the filter but I couldn't tell from what direction. Restarting it immediately was no problem after it stalled, no problems restarting it after it sat for 30 minutes either, one or two turns of the starter and it started right up. The engine continued to miss occasionally on the short ride back home though. Rechecked timing and it was right where I set it after the ignition work, 12 btdc without the vac advance hooked up. Vac advance is hooked up to full manifold vacuum
Nothing much has changed on the car in the last year that would cause me to suspect vapor lock as it was driven regularly on 100 degree days last summer and it was rock solid reliable. It uses a stock style mechanical pump with the oe charcoal canister and vapor return line. Fuel lines are all in the same place they were when it ran fine all last summer, engine doesn't seem to be overheating. I did switch from a 160 to a 195 Tstat but it was fine after I did that for months, and some weeks during this winter in FL were in the 90's. On the other hand the last few times it's had this issue it ran fine in the mornings when the motor was cold and started acting up after being driven a while.
The fuel pump I suspect had a bad checkvalve when I got it, as the fuel filter would empty within a few seconds to a few minutes of shutting the engine off and took a little while to fill it back up after starting. Engine always started quickly and it didn't cause drivability problems so I just left it alone. A new pump is on the way now and I'll be replacing it when it gets here in a few days but in the meantime is there any acid test to determine if it's vapor lock and not just a flakey pump? Maybe just a case of a bad tank of gas? fuel sock clogged? (it's probably never been touched since the car left GM) If I'm overlooking any easy or common issues/fixes I'd appreciate some advice as this is my daily driver/only car.