Cold start...cranks too long - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

 
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post #1 of 7 (permalink) Old Jan 15th, 02, 06:47 AM Thread Starter
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On one of the 69's, SS-350, stock as a rock except for the exhaust system, has a minor problem that so far has gone unsolved.

The engine runs great...I can actually idle it down to 450 arps and it still runs.

I recently rebuilt the original Q-jet and it too performs beautifully, except cold-starts take about 10-12 seconds of cranking before she fires right up. The choke is operational and is doing what it should. She hot-starts at the touch of a key.

Tonight I'll check to make sure I'm getting good spark during a cold crank, but I'm 99% sure that the ignition system is fine...it's all new except the stock distributor...and I do have the Petronix Ignitor which has worked great (no, it's not the Ignitor II which requires a little different cranking procedure...so I'm told).

I'm sure most of the fuel evaporates from the fuel bowl after a car is shut down...but why is it taking so long to get fuel back into the carb on cold-starts? Fuel pump? (the fuel filter is new though I like to forget...it only cost $35).

Any other ideas for diagnosis? Thanks in advance.
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post #2 of 7 (permalink) Old Jan 15th, 02, 09:35 AM
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The fuel doesn't evaporate from the bowl after shutdown. The bowl should stay essentially full until the next start, provided it isn't a month later.

It sounds like the choke doesn't close with enough pressure. Check that the choke is adjusted per manufacturers spec and that the spring is closing it tightly. On a cold morning, if you set the choke (by steping once on the gas) then open the flap with your finger, the flap should snap closed sharply, not in a slow mushy way.

Try stepping on the gas 5-6 times before cranking and see if that gets it to light up faster. If it does, you have a choke problem. If it doesn't, check that fuel is not leaking out of your carb through a porous casting, and that the float level is correct. The choke won't work if there isn't any fuel in the bowl.

I would bet dollars for dimes that the ignition isn't the problem! It's damn near impossible to flood a stock Chevy w/electronic ignition!!

[This message has been edited by PDQUICK (edited 01-15-2002).]
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post #3 of 7 (permalink) Old Jan 15th, 02, 10:10 AM Thread Starter
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PDQ...thanks for the advice. I'll give the choke another look, but it's snapped shut on cold starts, unless our temp is in the 80's...then it's slightly open. Also, the manifold-heated choke coil seems to operate fine...nothing broken or binding.

I set the float at 7/32 (I believe that's the spec) as per the kit's instructions. I was very careful with my measurement so I'm confident the float is set correctly...by the way, I used a new float on the rebuild.

Leaking inside the carb? Possibly, but my experience is you will hear liquid fuel spew/boil on the inside of the hot intake as it drips after a hot engine is shut down. I hear no evidence of that.

Any other ideas?

[This message has been edited by Sleepy-69 (edited 01-15-2002).]
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post #4 of 7 (permalink) Old Jan 15th, 02, 02:05 PM
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I had a 67 that did the same BUT I was using an oil-pressure shut-off switch feeding the electric fuel pump...so that the pump would turn on only after the oil pressure was built up..only a few crank turns was needed..
But in your case..which is stock...you can eliminate the igintion as the culprit by either pulling a boot (when off) and see if the boot snaps with a spark when turning the keys...or you can simply spray some starter fuild in the carb with the throttle wide-open then start the car and see...
Do you prime the carb by pressing the pedal to the floor a few times prior to starting???
Is there fuel squirting when you do this??
I would probably double check the float..make sure when setting the float to DON'T use your finger as it states in the instructions instead hold the float's hing pin then turn the carb body up-side down and allow the float to hang on it's own weight and make sure you hold the carb body level to ground ..then use the float gage to set it..5/16 is considered a starting point..
I would bet the choke is either too tight or too loose.. Adjust this when engine is dead-cold..let sit over-night or such..then slowly adjust choke till it just barely closes..One other note is to check ignition timing..and the cleanliness of the rotor and cap and plugs and wire..
Regards
Chris




[This message has been edited by cerrem (edited 01-15-2002).]
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post #5 of 7 (permalink) Old Jan 16th, 02, 04:11 AM
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Sleepy,

Yeah, I've seen more porous carb castings than I'd care to mention. Especially if you have an old "matching numbers" model.

Sometimes they gush, as you talked about, and then you can hear and smell the fuel boiling on the hot intake.

Sometimes they are sneaky and just seep a little bit. These are the ones that will drive you nuts! Just something else to look for.

You can also check for this by opening the choke flap and pumping the throttle a bunch of times. If the accelerator pump goes dry after a few shots, there probably isn't much fuel in the bowl. Make sure to run the engine afterwards to avoid gass washing the cylinders too badly!


[This message has been edited by PDQUICK (edited 01-16-2002).]
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post #6 of 7 (permalink) Old Jan 16th, 02, 05:21 AM Thread Starter
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Thanks guys.

Last night I double checked the ignition and she's gettin' clean spark.

PDQ...I had fabricatied a choke rod that's 1/4 longer for two reasons: 1) to compensate for the added height of two heat baffles (the thin ones) and three gaskets (I made a sandwich that really keeps the carb cool)...plus, I wanted the choke to open sooner. Last night I re-bent the rod so that now it's slightly longer than stock (1/16") and it reduced the cranking time to about 5-6 seconds. Like you said, perhaps the choke flap was flapping when cranking.

Cerrem...thx! I'll be taking off this carb again soon to change the primary jetting/rods and when I do I'll take another measurement of the float. I did use a a hi-cap needle and seat (1.35" orfice) so it's possible it's impacting the fuel level in the bowl, though it's seems this would keep the bowl more full.

Thanks again!
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post #7 of 7 (permalink) Old Jan 16th, 02, 05:26 AM
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I'm leaning towards what PDQ said in that it sounds like all the fuel is draining from the bowl. When you rebuilt the carb, did you do anything to the well plugs like epoxy or anything? My carbs used to all drain by dripping out the well plug holes that are prone to leaking over time. I then found some o-ring type plugs that you can replac the stock ones with and they cured all that. pretty simple to install.
also, what kind of fuel pump and filter to you have? Some mechanical pumps will let the fuel flow back to the tank which will drain the line. You can usually start the car but it will die quickly if that is happening, but worth a shot.

Lastly, check the choke. Sounds like it may be a bit too tight and I would suggest you only press the gas pedal once to set the choke then try cranking. Pressing it again will un-set the choke and it will try to go to normal idle while cold.

Good luck,
Bill C.


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Bill C.
Colorado Springs, CO

68 Camaro... someday!
71 Chevelle SS
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