Bogging down and stalling
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 763
Likes: 0
From: FBO Florida
Bogging down and stalling
Forum: Today I took it for a ride today and towards the end of a 45 minute run it decides to spontaneously bog down and stall as it is idling along in 4th gear. I pulled it over and it restarted. It did it 4 more times and intermittently was running rough for the rest of the way home. It even decided to stall going up the incline for a small bridge so I had to pull it to the side and back down until it cooperated. It did a light backfire through the carb just before stalling and once or twice on the cruise today.. I just restarted back at home and it seems to be idling fine. What are the culprits that I need to look at?
The details: The car has it's original stock 350 with smog pump and points distributor
The details: The car has it's original stock 350 with smog pump and points distributor
Last edited by 68AIR; Jan 26, 2019 at 03:51 PM.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Many things come to mind fuel starvation? Failing fuel pump, vapor lock?
could be flooding as well, like sinking floats, or junk stuck in the inlet valve.
Did it seem flooded?, and ran fine except for idle?
could be flooding as well, like sinking floats, or junk stuck in the inlet valve.
Did it seem flooded?, and ran fine except for idle?
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 763
Likes: 0
From: FBO Florida
Okay- a tankful ago I had to pump all the gas out of the tank because fuel had gone bad. I replaced the sender (different thread sender not accurate now). I usually always run 100 percent 93 octane but must have screwed up and then compounded the problem by letting it sit to long. It ran good last time out after the replacement fuel added. This time not so much as the trouble began about 30 minutes in to the drive. Carb has not been rebuilt recently. Things on my list for tomorrow include new fuel filter in the Rochester QJ, new condenser, swap out the coil and check the plugs and inside the cap/rotor. So it runs good before the trip and seemed to idle strong once I got back home and it had cooled a bit. After I do this I will report back.
Last edited by 68AIR; Jan 26, 2019 at 09:57 PM. Reason: Add additional details
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 763
Likes: 0
From: FBO Florida
What am I looking for in the bowl, sediment, rust, junk? If I do this do I need a rebuild kit for the carb (ie don't you have to unbolt the carb and take out the 5 screws for the air horn assbly for it to come off. I am worried the gasket will need replaced between the top air horn and the bottom float bowl assbly?
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
What am I looking for in the bowl, sediment, rust, junk? If I do this do I need a rebuild kit for the carb (ie don't you have to unbolt the carb and take out the 5 screws for the air horn assbly for it to come off. I am worried the gasket will need replaced between the top air horn and the bottom float bowl assbly?
Rev it up to 3000, then cup your hands over the air inlet till it almost stalls. Do this 3 or 4 times. The vacuum will suck all the crap out.
Probably not Lars approved, but I had some good luck with doing it on old cars.
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Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
The symptoms sound like a fuel starvation problem - the most obvious cause is a partially obstructed fuel filter. The backfire up through the carb is a sign of a lean condition, which will be caused by fuel starvation (plugged filter). Change the in-carb filter and make sure nobody has installed a second, in-line filter in the system. If the symptoms persist after changing the filter, it's time to install a fuel pressure gauge near the carb to check the pressure at the carb inlet when the problem occurs - I can post up a photo of a setup you can use to check this. 
Lars
Lars
Last edited by lars; Jan 27, 2019 at 01:45 PM.
