69 Cobra Jet Starting Issue - Ford Muscle Forums : Ford Muscle Cars Tech Forum
 
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post #1 of 6 (permalink) Old 05-17-2016, 11:10 AM Thread Starter
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69 Cobra Jet Starting Issue

Having some trouble with my 69 428 Cobra Jet and was hoping for some suggestions. I can't get the car to start without adding some gas to the carb. I had a leaking accelerator pump diaphragm so I changed that out. Carb seems to be shooting plenty of fuel in so if I add a little shot of fuel to the carb the car starts and runs no problem. Shut it off and it starts alright, yet if I leave it overnight and try to start it the next day, there is no way it will start. I'm at a loss..? Any suggestions? Motor was rebuilt 1400 miles ago as well as Holly Carb.. It seems to run excellent once it's going, but for the life of me I can't figure out why it won't start from a cold start..?
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post #2 of 6 (permalink) Old 05-17-2016, 11:36 AM
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Re: 69 Cobra Jet Starting Issue

ideas-

weak spark
plugged idle circuit
gas evaporating out of carb overnight (hot climates)
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post #3 of 6 (permalink) Old 05-17-2016, 11:48 AM Thread Starter
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Re: 69 Cobra Jet Starting Issue

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Originally Posted by cuthrell View Post
ideas-

weak spark
plugged idle circuit
gas evaporating out of carb overnight (hot climates)


The car hasn't been ran much in the past couple years.. It's not too warm where I'm at so don't think the gas could be evaporating..? Spark seems to be decent, but never thought of the plugged idle circuit... I will have to look into that.. Frustrating!!

1969 Mustang R-Code 428CJ
1968 Mustang C-Code 289
2007 Mustang GT/CS Convertible
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post #4 of 6 (permalink) Old 05-17-2016, 12:08 PM
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Re: 69 Cobra Jet Starting Issue

also may be worth checking that the choke is operating properly.
you're adding fuel to get it to fire when the engine is cold- that function should normally be served by the choke, in that it richens the mixture for you.
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post #5 of 6 (permalink) Old 05-17-2016, 01:43 PM Thread Starter
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Re: 69 Cobra Jet Starting Issue

Thanks I will check that out too..!! Appreciate the suggestions..

1969 Mustang R-Code 428CJ
1968 Mustang C-Code 289
2007 Mustang GT/CS Convertible
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post #6 of 6 (permalink) Old 05-26-2016, 05:15 AM
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Re: 69 Cobra Jet Starting Issue

sta-bil might help...i think it helps ethanol fuels keep from phase separation- even 10% ethanol if it sits long enough and draws a little humidity might separate out even in the float bowls- i am just 'bench racing' here, dunno if accelerator pump on your carb draws from the mid level of the bowl where its gas, or the bottom where the ethanol/water mix can settle...

see JC's thread in the galaxie section- hes put a primer pump on his hard to start without a shot of ether 390- either the htter spark approach(to ignite todays lower volatility fuels) or the primer(to fill/maybe even 'stir' the fuel in the bowls before pumping/cranking by refilling or at least topping off before starting).

doubt related, but easy to try- our 65 starts easier if i crank it a couple seconds before pumping the pedal FAST to give a better squirt into the carb with some air flowing- think it helps break up the fuel better? dunno, but seems to help a lot.

think JC is on the right frame of thinking with his double whammy approach- pump in fresh gas AND pour the fire to it in the form of a really hot spark. He is about to fire his up any day now, and surely he will be reporting back results in the coming days/weeks as to how easy she starts after sitting. I really think the 'primer' by stirring the float bowl even if only a little should help todays lousy gasoline- do think Sta-Bil could NOT hurt too, as the ethanol seems to make gas go stale or worse, split. just thinking aloud, *if* a carb is made so the accelerator pump inlet is at the bottom of the bowls, perhaps adding a riser tube might help, dunno, but would imagine that the most volatile stuff would not be at the bottom if its ethanol blended and humidity is present...

will be interesting to see everyones thinking on these things
good luck

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