Thing starving for fuel when stopping
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chief88
- Posts: 1
- Joined: Mon Mar 17, 2014 7:27 pm
Thing starving for fuel when stopping
Hello all- first post. Recently inherited a 74 Acapulco and have been having a great time learning and wrenching on it. Generally, it is running good- with one exception. It wants to die when I am braking/coming to a stop. It's not the act of braking - more the physics of decreasing the forward momentum. Need some advice. Could it be that maybe the carb bowl is not as high as it should be and when coming to a stop the fuel level gets too low? That's my only theory so far but would like some input please. It's just the basic engine and 34 pict carb...
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Marc
- Moderator
- Posts: 23741
- Joined: Thu May 23, 2002 12:01 am
Re: Thing starving for fuel when stopping
Float level would be on the list of possible causes. I'm assuming that there's no delivery problem (restricted pickup screen or filter, weak pump, float valve that's not opening fully or partially plugged by debris) since the primary symptom of that is stumbling under high demand...so a too-high float level is at least as likely as a too-low one - excess fuel could be sloshing out of the bowl vent tube and into the engine upon braking.
Later carbs with phenolic floats sometimes suffer from them absorbing fuel and gaining weight. If it's much over 8½ grams one can expect trouble. The top gasket often survives when the top is removed, but it'd be wise to have one handy - you'll probably find that a kit w/float valve costs about the same as the float valve and gasket do a la carte.
Does the car still have all the original emissions equipment (34PICT-3 carb or 34PICT-4, "SVDA" distributor, oil-bath aircleaner with functional thermostatic control system.)? With the SVDA, initial ignition timing at ~875 RPM should be 7.5° BTDC and it should not change when you disconnect/reconnect the vacuum hose to the canister.
Under the carb, is there an EGR valve? If it had one that's been removed, the passage needs to be blank-flanged off or welded shut. If it's still there but the exhaust side feeding it from the muffler isn't intact, it becomes in effect a variable induction leak that can disrupt the mixture. Loosening it enough to slip a strip of sheetmetal in to block the manifold package will suffice to disable EGR for troubleshooting purposes.
Later carbs with phenolic floats sometimes suffer from them absorbing fuel and gaining weight. If it's much over 8½ grams one can expect trouble. The top gasket often survives when the top is removed, but it'd be wise to have one handy - you'll probably find that a kit w/float valve costs about the same as the float valve and gasket do a la carte.
Does the car still have all the original emissions equipment (34PICT-3 carb or 34PICT-4, "SVDA" distributor, oil-bath aircleaner with functional thermostatic control system.)? With the SVDA, initial ignition timing at ~875 RPM should be 7.5° BTDC and it should not change when you disconnect/reconnect the vacuum hose to the canister.
Under the carb, is there an EGR valve? If it had one that's been removed, the passage needs to be blank-flanged off or welded shut. If it's still there but the exhaust side feeding it from the muffler isn't intact, it becomes in effect a variable induction leak that can disrupt the mixture. Loosening it enough to slip a strip of sheetmetal in to block the manifold package will suffice to disable EGR for troubleshooting purposes.