similar to vapor lock...?

Hello all,
I have a 1968 mustang with a 302. Most of the time, especially when the engine is cold, it starts just fine. Sometimes, more often when
the engine is hot than cold, I have to crank the engine for nearly ten or fifteen seconds before it starts, and then it catches, runs a little rough for a bit, then funs fine. Once or twice, it has not started at all after fifteen seconds of cranking. I really hesitate to even crank it for more than ten seconds, because I don't want to overheat the starter. The gas cap does not have a seal on it, which is why I doubt that it is vapor-lock related. The fuel line leading to the carb has a clear fuel filter, and it is always full or nearly full. The carb has float bowl gas windows, and they never drain. I was at one point having trouble with the accelerator jets draining into the manifold, but i corrected this problem by adjusting the accelerator arm. For reference, The carb is a Demon 625 cfm road demon jr. I have an electronic ignition module in the distributor made by crane cams called the XR-I. My normal starting procedure consists of pumping the throttle twice and turning the key- that usually works fine, except for the incidents described above.
Thanks for the help and input!
PS- anyone know any tips for finding vacuum leaks- I'm a bit scared to use the propane method. Maybe I'm a wuss :-D
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If the filter shows gas, then I agree that vapor lock is unlikely to be the problem. BTW, whether tank is vented or not is not an issue with vapor lock with mechanical fuel pump. It is just that a fuel pump cannot pump vapor, only liquid.
Now, what may well be the problem is something else that is richening the mixture. I don't know for sure what kind of a float that Mustang carb has, but a leaky or fuel soaked float can cause rich mixture and starting problems. Leaky needle valve in float chamber can also do this. I'd get carb rebuilt.
BTW, there are other ways to find vacuum leak. Ear, water, oil, etc.
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sounds to me like your describing a flooded condition, now you just have to narrow down why. KB If the car is warm the 2 pumps will deff. flood it.
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On 23 Mar 2007 16:36:15 -0700, "bobar3425"

One thing I notice is that the glass fuel levels are always full. IIRC, the Demon is basically a Holley. If this is true, the correct fuel level is at the bottom of the hole in which case you should not see fuel. If you see the fuel, the float is probably too high causing flooding and you need that 15 second crank to clear a flooded condition. IIWY, I would try lowering the float level. Make sure the fuel pressure is correct. It is possible that the float needle is leaking a bit allowing the fuel level to rise after shutdown. You need to make sure the fuel level is correct both running and stopped. If the fuel level rises after shutdown and/or the fuel pressure drops, your float valve and/or pump check valve is leaking resulting in a high fuel level/flooded condition. If you do not already have the Holley tuning and service manual, it is well worth the cost.
Lugnut
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bobar3425 wrote:
My normal starting procedure consists of

Do you do that when its hot? If so, DON'T. Try cranking it without pumping the throttle, or by holding the throttle 1/2 open while cranking until the engine catches.
Modern fuels, especially "winter blend" fuels, have a very high vapor pressure and are more prone to a) vapor locking and b) "boiling" out of the carb when the engine is shut down hot, and then pooling in the intake as it cools. I suspect that the problem is the latter in this case, and that by pumping the pedal twice with the engine hot you're adding more raw fuel to that already pooled in the intake and creating a flooded condition.
But also be aware that a weak ignition component will also show up under heat-soak conditions, so it may be that you're getting a weak spark or NO spark when trying to start the hot engine.
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Hey thanks for the responses everyone!
I will adjust the float levels and check the ignition system!
Thanks again!
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