Carbed ls motor hard to start hot or cold - Hot Rod Forum : Hotrodders Bulletin Board
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Old 10-31-2011, 07:22 AM
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Carbed ls motor hard to start hot or cold

I have a carbed 6.0 ls motor with a 650 edelbrock avs. I have a hard time starting when cold and when hot. The weird thing is the first couple times i fired it up it started right away. I am using the msd 6010 ignition box and I've tried all the pills all with the same result. it sputters and pops and has even shot a little gas back out of the carb. Once it's running it drives great and idles fine. If i shut it off even for a second it's hard to start again 90% of the time (sometimes it starts right back up). Thanks for any suggestions.http://s370.photobucket.com/albums/o...wap%20caprice/

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Old 10-31-2011, 01:22 PM
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Then I would say check to see if the carb is leaking down or if it`s getting heated after shut down. Sometimes the use of a thin carb gasket causes the carb to get really hot after shut down which causes the fuel to evaporate.
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Old 10-31-2011, 04:57 PM
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how can i tell if it's leaking down? I have a holley blue pump and i have noticed that after i shut off the car the fuel pressure gauge goes back to zero. not sure if that's normal. when i have the key on fuel pressure immediately goes to 6 psi
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Old 10-31-2011, 06:12 PM
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Other than the carb leaking and emptying the bowls, there's a possibility it could be flooding the intake/cylinders as well. After it sits a while see if you have a shot from the accelerator pump nozzles when you open the throttle, with the key off.

It's normal for fuel pressure to drop when the pump isn't pushing fuel to the regulator or carb. If it's hard to start within seconds of shutting off, and you're not pumping it on restart, it sounds like what DV said, flooding.
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Old 10-31-2011, 06:50 PM
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Carb float levels

Check and make sure the Carb float levels are correct high fuel levels will drain and wash the oil off the cylinder walls and make starting all but impossible until it dries up

Last edited by rsfyj; 10-31-2011 at 06:51 PM. Reason: missed a phrase
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Old 11-03-2011, 06:37 AM
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I checked if the carb was leaking down and it was fine so i put my thermal gun on all the lines and carb after i was up to temp and didnt see anything crazy. later that day i got my cable to connect my laptop to the msd box so i plugged it in and low and behold it said cam snsor fail so i went to remove my cam sensor and noticed the plug was loose so i secured it and all is well. starts with a turn of the key and no pedal now. I do have an off idle bog at wot and another bog from mid throttle to wot so once i work that out i'll post up some vids for everyone to enjoy. thanks for the suggestion guys i guess i had a brain fart and didn't check the obvious first. i still don't know how it was running at all without a cam sensor signal?
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Old 11-03-2011, 06:55 AM
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Check the input voltage at the MSD box. It could be marginal until the car starts and the voltage rises due to the alternator kicking in. Low voltage could be a bad connection, bad or undersized wiring, bad ground etc. The power to the MSD box is supposed to come directly from the battery.
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Old 08-31-2012, 08:13 AM
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Quote:
Originally Posted by T-bucket23 View Post
Check the input voltage at the MSD box. It could be marginal until the car starts and the voltage rises due to the alternator kicking in. Low voltage could be a bad connection, bad or undersized wiring, bad ground etc. The power to the MSD box is supposed to come directly from the battery.
I have the same problem - mild SBC w/ Accel points eliminator ignition, MSD6, new engine. Very hard to start. Just found out that the alternator is fried so I'm thinking the MSD is not performing due to low voltage. I hope that's it. I know this combo can work very well - my 354 hemi runs a Chrysler A series electronic ignition w/ MSD5 box and it starts at a touch of the key, regardless how hot the engine is.
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Old 08-31-2012, 04:17 PM
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I see you have your MSD box mounted on the intake. It should be mounted away from the engine. It is possible that the ignition box is getting heat soaked when you shut the engine down, thus cause hard starting. Just a thought. By the way, How does that car go? Is that a stock 6.0 liter? Whats it out of???
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