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340 takes a long time to start

RamRod

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Hi everyone. This forum has been a great place and has helped me out a ton. I have another stumper for everyone.

I have a 1970 340, which takes a long time to start. Every day, the Carberator bowl is empty. I had it running yesterday, but today it was completely empty again. I do not smell raw gas in the garage, so I don't think that it is evaporating or leaking anywhere. I had another carb that I put on, because I thought that the carb was leaking somewhere, but I have the same thing happening. So I don't think that it is the carb. Could it be the fuel pump?

Thanks,
RamRod
 

Chryco Psycho

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It is evaporating , fuel is not the same as it was years ago .
I would recommend blocking the heat cross over through the intake & you can use a thin isolator like Coolcarb sells to drop the temp 75* or more in the carb .
 

RamRod

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I thought about the electrical fuel pump, but I want to keep the car as close to stock as possible. Where would it be evaporating from? Isn't the fuel bowl a closed system?
 

toolmanmike

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Nope, it evaporates out of the bowl vents. I shut mine off and with a hot engine (called heat soak) you can hear the fuel boiling in the carb. The puppy pee gas we have nowadays boils at a fairly low temp. A fuel filter with a return line helps while the engine is running but what happens after you shut the engine off is hard to stop. A thick carb base gasket helps. Carter/Edelbrock are more susceptible because the float bowls are directly above the intake and carb base. Holley's are much better because of their overhanging float bowls on many of their models. Like CP suggested, a electric priming pump can work wonders. Let me find a popular number and I will repost it. A momentary pushbutton switch works well and can be hidden under the dash or in the ash tray or glove compartment.
 
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toolmanmike

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A little pump like this would work fine. The mechanical pump will pull fuel through this one when it's not running.


fuel priming pump.jpg
 

RamRod

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Thanks. Can I run it online with the other? Series? Or does it need its own line?
 

toolmanmike

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Thanks. Can I run it online with the other? Series? Or does it need its own line?
Yes in series and you run it in addition to your mechanical pump. The electric is just used to fill the carb up after the fuel evaporates. Just a momentary switch so it doesn't run constantly.
 

toolmanmike

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Here is a good thread on FABO you may want to read. Losing Fuel

 

Chryco Psycho

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You can also switch to EFI , Fitech & Fast are around $1000 & then you do have a sealed fuel system
 

CMC

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What issues have you seen with EFI?
 

k2steve

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What issues have you seen with EFI?
The biggest problem I had was a clean 12v power supply, my battery is in the trunk. I finally run a dedicated line and a switch under the dash as a last resort to get the Fitech to work halfway right.
My trouble was hot starts(flooding). It fixed that and the idle speeds for the AC on/off.
 

CMC

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Yes, hot starts. we solved that issue with a new coil...

Purrs like a kitten now, hot or cold.
 

Chryco Psycho

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In the earlier days I have seen a number of EFI controllers die , I have seen fuel pump inlets get clogged so the tank has to be clean , longevity can be a problem with some of the cheaper systems . sensors fail even on factory EFI systems .
 

RamRod

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Thanks everyone for the suggestions. I put the inline electric pump in the other day. Picked one up from NAPA and put it in, and got the switch under the dash. Now all I have to do is prime the carb for 2-3 seconds, pump the pedal twice and it fires off right away. Works great now.
 

Scoop

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Hello. I have a 74 Challenger with a 340. It was very hard to start when cold. Not as bad when warmed up but still. I would have to pump the gas 7 to 10 times to get it going. Not knowing when the last time it was tuned up, and I figured the distributor was original. I got a distributor kit from Summit Racing, that included the coil, ballast and electronic module and wiring. My mechanic installed it just last week. What a difference. If fires right up now and sounds even better. I hope that helps and that you find a fix.
 
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