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Discussion Starter #1
If my car sits for a long time, I have to crank if alot before it finally starts. I'm running an Edelbrock carb and Holley mechanical fuel pump. If I start the car a day after it's been running, it fires right up.

What causes this? Is the fuel evaporating out of the carb? Can this be fixed?

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68 468 700R4, and here it is;
mutert23
 

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Fuel is leaking down out of the carb,
After shutting it down when its hot pull the air cleaner, smell for raw gas etc,
Don't know about your brand of carb, but the Q-jets have a lead plug on the bottom that is prone to leaking over night.
 

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Mine does the same thing with a Holley DP.

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Rick Dorion
69 RS Conv,355,Autogear M22,4.10's and I don't worry about stone chips ( yet ).
 

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Both my Q-jet and Demon to that, but only if it sits for a week or longer. The Q-jets plugs have been epoxied too.

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1969 Base Camaro
Vortec 355, Perf. RPM, Demon Carb., TH-400
All sheetmetal is NOS GM
See my webpage at: http://www.geocities.com/compuboy007/

[This message has been edited by Silver69Camaro (edited 11-15-2002).]
 

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I have the same trouble with my Holley 650 DP, its even worse if the weather is a bit on the cool side...I think I have to mess around with my choke more though.
 

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Discussion Starter #6
I'm running a brand new Edelbrock 800 carb. So I guess there really isn't anything to do to fix this?
 

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on my old 350 with a quadrajet did this, but when i put my 750 demon dp (no choke) on it it started perfect every time. and after i put my 406 in, its still the same, a quick single pump when cold and it starts right up, and just hit the key when its warm, no problem. i would think you should be able to achieve this w/ your car as well, with some fine tuning/adjusting.
 

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Basically the fuel is just draining out of your fuel bowls down the line and into the tank. Just gravity, unless its leaking out the carb onto or into your intake you have nothing to worry about.
 

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The fuel isn't likely to be siphoning back into the tank! It's leaking into the intake and down the cylinder walls into the pan. If you get enough fuel in the oil pan, you could blow the valve covers and the oil pan right off the motor. (seen this happen! Kewl! wasn't my car!) If you are lucky enough for this not to happen, you could dilute the oil enough to ruin the bearings and/or seize the oil pump. If this is a new carb and it's leaking, take it off and get another one under warranty! or get it fixed.
Jim
 

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I dunno 'bout that...my Demon does it, my Qjet does it, my old Edelbrock 1406 did it, and my new 625CFM Carter did it. I think the fuel is evaporating out of the fuel bowls, personally. But this is after an extended period of time though...not just a couple of days.

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Matt Jones
1969 Base Camaro
Vortec 355, Perf. RPM, Demon Carb., TH-400
All sheetmetal is NOS GM
See my webpage at: http://www.geocities.com/compuboy007/
 

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If you look closely at the mechanics of a float/needle and seat set up. It's like a toilet tank. The fuel is sitting below the valve that allows fuel to flow into the bowl. There is no way for the fuel to get back up there. In a Holley or a Demon, it would have to siphon two tanks empty. Also, the fuel pump works like your heart. One way clapper valves prevent fuel from draining back on the pressure side of the pump. The only other possibility besides leaking would be percolation. There may be enough heat soak into the carb to boil the fuel out.
As mentioned in the earlier post, a Q jet has a problem with a lead bowel plug that can leak. But then again what does MarkM mean by "a long time". Your suggestion of fuel evaporation might be the case?
Jim
 

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Something's fishy, Mark. If I let my car sit for days, or a couple weeks, all I have to do is to pump the pedal once, and it fires on first try. Always. How's your timing? If you don't have enough advance at initial, it could crank a bit before catching spark.

If you think it is losing fuel, wait a couple days and then open the air cleaner, poke you head in there, and manually push the throttle plates. Look for gas out of the accelerator pump. If you get some, the issue is not fuel leakage/evap.
 

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i have seen problems like this fixed by putting in a fuel pump. perhaps the check valve goes bad or something, and allows the fuel to drain back.

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1971 Nova(looks like 69 camaro from underneath!)
355sb, vortec heads, HOT cam,T-10 tranny, 3.70 gears 16X8" IROC wheels. 12" Corvette brakes on the way.
see pics here http://community.webshots.com/user/novaderrik
 

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ihave a 1406 edlbrock also, AND a brand new fuel pump with a Mr Gasket glass in-line filter. you can actually watch the fuel level in the filter decrease over time. it IS draining out of the filter and fuel line back to the tank. absolutly! i have investigated this by disconnecting the line from the tank to the pump and putting a bowl under it. it happens, no big deal.
 

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hey mark,

got a novel idea. get fuel injection.....lol...

but i have to agree with the evaporation/or leak down... have had the same proble. i think that it may evaprorate a bit from the vent tubes....ever take off a carb turn it over to drain it and watch the fuel come from the vent tubes?

i agree with Mean and CAm... if you stab the throttle and see the gas pump from teh accelerator, then there is still fuel in the bowl....

good chance that the fuel is possibly draining back to the tank and you have to crank it to get it back to the bowls... you could get an electric fuel pump and see if the gas gets there sooner...

HTH, JS
 

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i know some circle track sanctioning bodies require a one way check valve in the fuel line. maybe get one of those?

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1971 Nova(looks like 69 camaro from underneath!)
355sb, vortec heads, HOT cam,T-10 tranny, 3.70 gears 16X8" IROC wheels. 12" Corvette brakes on the way.
see pics here http://community.webshots.com/user/novaderrik
 

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Discussion Starter #17
Thanks for all the advice. I'll see if the carb shoots fuel out the next time I try to start it.
 

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Worn fuel pumps will allow drain back. But there should be plenty of fuel in the carb to start the engine. Mechanical fuel pumps, by law, must meet anti drain back and anti siphoning specs so that in the event of a roll over or an engine fire there will be minimal fuel flow. Electric fuel pump systems have what's called a roll over valve. If you can see your fuel filter draining back to the tank, check the filler cap. You may have a defective or damaged cap, or someone may have installed a newer style cap that is non venting and the fuel is being sucked back into the tank. If your cap is the right one then your pump is worn or faulty. This doesn't mean your pump won't work, just that the safety features aren't working the way they should. I leave my cars in storage up to six months and have never had empty fuel bowls. If yours are empty after just a few days, I would suggest that a)It's leaking b)It's leaking or c)It's leaking. Not trying to be funny here! but where else can it go? For this much fuel to evaporate would take a long time (months)or there is a lot of heat involved.
Jim
 

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I have the same problem. I just got online to post the very question, but you beat me to it. I took off the stock quadrajet and lost the built in check valve that the Qjets have. I put on an Edelbrock 4011. It did the same thing with the Holley 750 that I had on it. I also have a new stock fuel pump putting out good PSI. I have the stock venting gas cap that works fine. I can sometimes hear the gas pouring back into the tank. Does anyone know it someone makes a filter with a built in check valve or an inline check that won't restrict gas flow? Thanks for the help!!

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69 SS 396 ragtop Clone/M-20/331 12 bolt posi/Lemans Blue/White Hockey/ Black Rag/Black deluxe Interior
Ragtop Pics http://hobbystage.net/camaro/kenth/
 

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I also thought of the check valve idea about a year ago, and found that it won't help. The pressure in the line will eventually get through the needle and seat, and won't solve the problem.
Jim McFarland also had the same experience with the check valve idea.
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Matt Jones
1969 Base Camaro
Vortec 355, Perf. RPM, Demon Carb., TH-400
All sheetmetal is NOS GM
See my webpage at: http://www.geocities.com/compuboy007/

[This message has been edited by Silver69Camaro (edited 11-24-2002).]
 
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