67 GTO Pontiac 400 stallling! - Pontiac GTO Forum
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post #1 of 15 (permalink) Old 07-24-2012, 10:13 PM Thread Starter
 
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67 GTO Pontiac 400 stallling!

Hey guys, so i had the car out this weekend, all weekend after putting in a new HEI distubtor and wires. Was driving it for a bit and then it got up to 190 degrees and it started stalling. After stalling though it starts right back up. The car runs great and it like it should all the way to about 190 degrees once it hits 190 or above it will stall like crazy .It stalls at idle sitting at light or just idling along with no gas. Any one have an idea on what this could be from? im stumped i cannot figure it out
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post #2 of 15 (permalink) Old 07-24-2012, 10:45 PM
 
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As long as your not losing spark I would start with adjusting the carb with it fully warm. Possible bushings bad in the throttle plate Easy check. What is your idle rpm? Does it shutoff or act like it's running out of gas?

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post #3 of 15 (permalink) Old 07-25-2012, 12:23 PM Thread Starter
 
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Yeah i was thinking it was a carb adjustment but this is semi new to me. i dont know how to properly adjust the carb without making it worse.=[ The idle RPM is around 900 -1000 RPM and no it will just cut right out with no sputtering or any sign of stalling.
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post #4 of 15 (permalink) Old 07-25-2012, 01:47 PM
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Is your choke working correctly? Does it start doing it as soon as the choke comes off? My first thought for anything that seems to be heat related is to be suspicious of vapor lock. Does your fuel system have a vapor return line and are you using it if it does? Check the routing of all the lines into and out of the fuel pump and make sure they're not "close" to anything where they'd soak up a lot of heat.

As far as adjusting the carb, start by turning in the two mixture screws until they're lightly seated, then open them both 4 maybe even 5 full turns. That should put the mixture pretty far onto the rich side. Once the motor's started and warmed up, first set your idle speed down to where it needs to be (or where you want it) then take them one at a time and slowly close it until you reach the point where the you can tell the engine is starting to run a little rough... open it back up slowly until it smooths out again. Do this on both sides. Do both sides a couple of times starting from your previous "best" setting and resetting your idle speed each time. That should get you dialed in pretty close on the idle mixture.

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post #5 of 15 (permalink) Old 07-25-2012, 02:17 PM
 
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with an idle at 900 rpm and it shutting off like a switch I would check into ignition. What wire did you use for power? Not the orginal coil wire I hope. It's a resistor wire and drops voltage.

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post #6 of 15 (permalink) Old 07-25-2012, 05:04 PM
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I agree with face. Fuel will stumble and roughen before a stall-out. I suspect it's that darn "Upgraded" HEI.....a hot module or pickup coil. Throw the standard dizzy back in and enjoy worry free driving.
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post #7 of 15 (permalink) Old 07-25-2012, 08:54 PM Thread Starter
 
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Bear- the choke has always seemed to give us a problem.i do not know if its heat related but it does it when it does reach 190 degrees and over. Where would be the vapor return line be?

Face if it was the coil resistor wire wouldnt it do it all the time? and we did use the wires off the original coil. Whats the situation with coil resistor wire and giving power to the distrubutor?
Im thinking its definitly either one of them just got to trouble shoot both.
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post #8 of 15 (permalink) Old 07-25-2012, 09:11 PM
 
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The voltage drops to around 6 when running on that resistor wire. While cranking it has 12v. Run a wire from the battery to the dist. Drive it. Possability the lower voltage could affect the coil or module in a negative way and taking one out. But you cannot run on the resistor wire to something needing 12v

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post #9 of 15 (permalink) Old 07-25-2012, 10:33 PM
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With a points system, upstream from the wire that connects to the coil there's a circuit that actually feeds power to that coil wire from two different sources. In the START position it's getting a full 12 volts to help start the engine, but in the RUN position it switches over to feed through a resistor wire and it gets a lot less, 6v I think fac said. It does this to save your points --- running them from 12v all the time would cause lots of arcing across them and they wouldn't last long. Most HEI's need the full 12v all the time to operate correctly. That means you've either got to find the resistor wire in the circuit and bypass it (good luck with that, I never did find mine), or "do something else". Thanks to some smart dude on here what I did was get a headlight relay and connect it via heavy wire straight to a 12v source and then into the HEI. I use the wire that originally went to the coil to trigger the relay. This way I know I've got full power to the HEI, and if for some reason I ever decide to go back to a points system all I have to do is connect the coil wire back to the regular spot and I'm done. Making sure you're getting a full 12 v to the HEI all the time is worth doing even if that turns out not to be the cause of your problem.

Vapor return. If your car has one, there'll be two lines coming off the tank and going up to the fuel pump, one larger than the other. The larger line is the pump feed, the smaller is the vapor return and it connects to a 3rd fitting on the fuel pump. It doesn't take much heat to cause gasoline in the fuel line to get hot enough to boil, and when it does and vaporizes in the line - you lose fuel to the engine. Fuel pumps don't move vapor very well. As long as fuel is moving through the line quickly you tend to be ok because the fuel is cool coming out of the tank. The problem tends to occur when fuel flow is very slow, or stopped and the fuel in the line has enough time to get hot enough to vaporize.

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post #10 of 15 (permalink) Old 07-26-2012, 06:15 PM
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I've run into a bunch of HEI set-ups that fail when hot (and internal resistance increases). Modules and pickup coils. Not in the wiring itself. They work fine cold, and when hot, nada.
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