Air in fuel line - Team Camaro Tech
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post #1 of 6 (permalink) Old Jan 30th, 03, 01:11 PM Thread Starter
 
Join Date: Jul 2002
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I have a '73 Z with a Holly. I have a clear fuel filter in line and can see either the fuel is draining out of the line. Should the fuel pump hold the fuel up in the line, or is there a check valve in the carb?
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post #2 of 6 (permalink) Old Jan 30th, 03, 05:13 PM
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You'll probably always have air in there above where the outlet to the carb is. You could tilt to get air to feed to the carb and make it a full of fuel filter. I just remember always seeing air in a friends 65 gto with the 389 or aluminum 427 under the hood. Oh yah. You'ld have to tilt the filter with the engine running of course.
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post #3 of 6 (permalink) Old Jan 30th, 03, 05:58 PM Thread Starter
 
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I mean there is NO fuel visible in the filter. The filter is mounted vertically and is between the fuel pump and carb. I have to pump the pedal 10-15 times when the car is cold to get enough fuel in the bowl. Car runs great until I park it for a few minutes. As soon as I stop the engine, I can see the fuel receding from the filter. If I get back in the car and turn it over, it will fire right up. Unfortunately about 1 or 2 minutes later, the engine will stall (usually about the time I'm pulling into traffic). I assume it's the air bubbles interfering with the fuel flow. I was just wondering whether the fuel pump should keep the fuel from running back to the tank. Anyone?
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post #4 of 6 (permalink) Old Jan 31st, 03, 12:02 PM
 
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I had a similar problem on my 454. Turned out that after a little warmup from a cold start, the fuel in the line would flash to vapor (i.e. vapor lock). If I was driving it at the time it would start to cut out. I actually stood there one time with the hood open and watched it flash over to vapor (clear fuel filter). A combination of things were causing this, including they way I ran my fuel line from the pump to the carb (too close to heat sources), and my failure to bypass some fuel flow to the fuel tank, as was done from the factory on this car. After fixing these things, no more vapor locking. Later I added an insulating spacer under the carb to minimize fuel boil off after shutting the engine down hot. This eliminated excessive cranking after things like stopping for gas or lunch etc.
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post #5 of 6 (permalink) Old Feb 1st, 03, 08:03 AM
 
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If your car is stalling out when you are trying to accelerate, it is probably a bad fuel pump. Put a fuel pressure gage in between the pump and carb...I think it should read @ 6 PSI.

As for fuel draining back from the filter, my filter is horizontal and if the car sits for a long time, it will drain to about half. But this is because it is horizontal compared to your vertical set up. Check the fuel pump.


[This message has been edited by Kens68 (edited 02-01-2003).]

[This message has been edited by Kens68 (edited 02-01-2003).]
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post #6 of 6 (permalink) Old Feb 3rd, 03, 09:16 AM Thread Starter
 
Join Date: Jul 2002
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Good advice. I'll start with the fuel pump and make sure the drain line is clear all the way back to the tank. Thanks.
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