vapor lock or timing
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vapor lock or timing
Truck cold starts just fine, drive fines. Struggles to start after driving for like 30 or more minutes. Feels like dead battery but read 12v when off 14v when running. Let it sit 15 to 20 min it starts fine. Original exhaust manifold with heat shield. New 200 amp alternator. Upgraded from 2bbl to 4bbl. New intake .
How do I diagnose if it's vapor lock or timing? Or do u all think it's something else
How do I diagnose if it's vapor lock or timing? Or do u all think it's something else
Laughing Gas
Joined: Nov 2013
Posts: 1,207
Likes: 60
From: S.E. Louisiana;so far USA
You have some good suggestions already.
If the ignition timing is too far advanced it would oppose the spinning of the engine by the starter, but would likely do it hot & cold. Vapor lock would deprive the engine of fuel. Too much heat on the carburetor might cause fuel percolation and flood the engine for a while. Too much heat to the starter motor could temporarily weaken it. The 12V and 14V values are a bit on the low side, but could be gauge inaccuracies. A blown head gasket could allow a bit of coolant into one cylinder, but you would probably notice that in other ways. I am assuming that when that new manifold was added the problem was not added also at that time. If so look for unsealed bolts allowing coolant to enter a cylinder or a gasket which leaks coolant a bit when hot.
If the ignition timing is too far advanced it would oppose the spinning of the engine by the starter, but would likely do it hot & cold. Vapor lock would deprive the engine of fuel. Too much heat on the carburetor might cause fuel percolation and flood the engine for a while. Too much heat to the starter motor could temporarily weaken it. The 12V and 14V values are a bit on the low side, but could be gauge inaccuracies. A blown head gasket could allow a bit of coolant into one cylinder, but you would probably notice that in other ways. I am assuming that when that new manifold was added the problem was not added also at that time. If so look for unsealed bolts allowing coolant to enter a cylinder or a gasket which leaks coolant a bit when hot.
Postmaster
Joined: Nov 2011
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"Feels like a dead battery" means (to me) slow cranking. Is it kicking and bucking as it tries to crank or just slow? Kicking and bucking would suggest timing issue. Just slow would suggest 1) weak and/or heat soaked starter 2) poor connections 3) weak battery.
As a first diagnostic (easy things first), suggest cleaning all battery + and ground connections. Visually inspect wires for deterioration, clean connections with emory cloth and tighten well. If the problem persists, suggest you get the battery tested for free at a local AP store. After that, maybe new/reman starter.
As a first diagnostic (easy things first), suggest cleaning all battery + and ground connections. Visually inspect wires for deterioration, clean connections with emory cloth and tighten well. If the problem persists, suggest you get the battery tested for free at a local AP store. After that, maybe new/reman starter.
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New User
Joined: Nov 2014
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Thanks to all. I seemed to fix the problem. It was several things. Timing was slightly off. Electric choke was not set right so I just disconnected it. Never liked electric choke.had to adjust air fuel and idle on new carb.
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