Idle acting crazy

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phish1270

phish1270

phish1270
Joined
May 18, 2009
Messages
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Location
Iron Station, NC
This is a recent development with the way my car is idling since it has started getting up into the high 80s in NC already. I had vapor lock issues last summer & thought I had taken care of them but it is acting up again. I can't have the car not drivable when it gets hot or I won't be able to drive it again until October. I have replaced just about everything I can, new 1/2" spacer under new Edelbrock 1406 600cfm 4 barrel carb, new fuel pump, fabricated a heat shield to put between fuel pump & exhaust, insulated the fuel lines, new fuel filter & put a 180 t-stat in help it run cooler. The car is not running hot at all. The car is a '65 Barracuda with an early 70s 318 auto in it. The motor was in the car when I bought it so I do not know that much about it. Converted to electronic ignition last winter.

The issue: When I am sitting at a light in traffic the idle is around 500 rpms, as I am sitting the idle starts to drop until it is barely chugging around 200 rpms. If I slip the car into neutral the rpms start to very slowly climb until they get back up to around 900. I have also noticed that sometimes when I turn the car off the clear inline fuel filter is empty. I think I am still having some sort of vapor problem. Is it possible that the fuel is cooking in the line while I am sitting at a light? I really need some help here guys! Thanks ahead of time.
 
idling hot, is it dripping excess fuel into the engine through the carb? Mine was doing this, I set the float level WAY LOW for troubleshooting and it was much better. FAQs on Edelbrocks website said that is an issue unless you run a fuel press regulator and drop the fuel pressure to around 5.5 psi. below text is from their website... higher fuel pressure will overpower the needle and seats and flood the carb...

Q: I see fuel dripping from the carburetor boosters at idle, what causes this?

A: Too much fuel pressure usually causes this and often times dirt in the float bowls can do the same. Make sure your fuel pressure does not exceed 6.0 psi, optimum pressure is 5.5 psi.
 
I will check & see if it is dripping fuel at all tonight. I know I smell fuel all the time. I am running a stock fuel pump, I do not know what psi it puts out. Would flooding the carb cause the idle to drop like that to where the car almost seems like it is going to stall but then recover just from putting it in neutral? I have never messed with the float level. I guess I need to do some research, is it hard to adjust? Thanks for the advice.
 
Sounds to me like the fuel is being heated up too much.
Do whatever you can to get the line away from heat. Try wrapping it in something insulative.
 
I have insulated my fuel lines by splitting another fuel line & zip tying it around the ones on the car with the split facing up to allow heat to dissipate. I really do not understand why it clears up in idle, it is weird. It is not like the idle is too low & I have to put it in neutral every time I stop just when I get stuck at a long light. I do not touch the gas pedal at all, just slip it into neutral & the idle slowly starts to recover.
 
Check to make sure your tank is venting(vent tube)it could be blocked causeing pressure in the tank?
 
I think you guys are on to something.
Somewhere I read that vapor lock can cause a momentary overpressure condition between the fuel pump and carburetor causing the fuel in the line there to be forced into the carb, overwhelming the float needle valve, causing a little flooding. Did I dream that or read that..?
I insulated my fuel lines on my Volare with black foam pluming insulation and zip ties in the pasts, as far back as I could get under my car, about half way back to the tank. That cured my vapor lock issues.
It is strange that if you put your car in neutral the issue clears itself, maybe just the removed load allows the engine to rev up and clear the fuel as well as the the fuel pump can operate more effectively as the revs come up. Does your stock fuel pump have a return line type process? I think those deal with vapor lock better.. I don't now much about fuel systems of these era Mopars as of yet.
One thing to think about when you wrap a solid rubber fuel line around your existing line for insulation.. Solid rubber is a pretty good conductor of heat, a foam or other insulative material (wrap) would yield much more effective in preventing heat conduction to the fuel line. Maybe detach the entire fuel line as far back as you can go, and wrap header wrap around it all!
When I assemble my Duster, I am doing some serious fuel line insulation and wrapping my headers too, that way if I have to work on either, It will take me a year to get at it... hehe..

My two pennies worth..

:)




phish1270 said:
I have insulated my fuel lines by splitting another fuel line & zip tying it around the ones on the car with the split facing up to allow heat to dissipate. I really do not understand why it clears up in idle, it is weird. It is not like the idle is too low & I have to put it in neutral every time I stop just when I get stuck at a long light. I do not touch the gas pedal at all, just slip it into neutral & the idle slowly starts to recover.
Click to expand...
 
If it is the excess fuel dripping problem, putting the car in neutral will allow it to idle just a bit higher and not be affected quite as much by the extra fuel. I also have a stock fuel pump and have been plagued by the fuel dripping issue I described above. Mine would be intermittent, adjusting the float level lower helped the issue greatly. Floats are not hard to adjust but if too much fuel pressure is your issue, float level is only a bandaid or temporary thing to try for troubleshooting. I did that for troubleshooting but it is not the right answer. A fuel pressure regulator is. The fact that it is an FAQ on Edelbrock's website should say something!
 
Got under the hood at home & I do not see any fuel dripping while in park. had the wife sit in the car with it in gear & still do not see any excess fuel dripping into the engine. The fuel is sputtering into my clear fuel filter, not sure if that is normal. It is a new stock fuel pump but I guess it could go bad. Should my fuel filter be full of fuel when the car is running or will it be intermittent? My fuel pump does not have a return line. I am ordering heat tape to wrap everything, the split rubber hose was another members suggestion last year & I thought it worked then for the vapor lock. There appears to be a smaller tube running to my fuel tank along the filler neck, should be the vent. How to I check it? It is hot under the hood, I really do not see how anything works in that kind of heat. Could it be bad fuel? Thanks for all the suggestions guys.
 
I have been messing with the car all week. I have adjusted the fuel mixture screws & the idle a bit. I also had a possible vacuum leak since 2 of the carb bolts were loose. None of the carbs or gasket kits come with lock washers but could I use lock washers to help keep the carb tight? Or do I need to just get in the habit of checking them regularly? I will post if I have things ironed out or if it keeps happening. Thanks for the help.
 
I run lock washers on my carb nuts. My fuel filter does the same thing sometimes at an idle.
 
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