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70 383 Roadrunner: Won't start unless carb is primed!

Bradley 70 RR

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I finally got my 70 Roadrunner going after many years of sitting. I primed the motor, cleaned the fuel system, and had carb rebuilt. The problem I have now is it won't start unless you pour a little gas in the carb first. It runs pretty good after that, but hesitates upon full throttle. I was thinking maybe accelerator pump was faulty? Any insight would be greatly received.
 
Based on your description I would certainly check the operation of the accelerator pump. There should be a fairly strong stream of fuel coming from the acc. pump nozzle when you open the throttle. You can check this with the engine not running, and air cleaner off.
 
Lets start out ,what type of carb is it,afb ,holley,also the fuel pump how old?
 
Make sure there is a vent in the gas tank or the gas cap, it might be vapor lock,also see if there is gas in the filter.After It's been running shut the car off.Now take the air cleaner off lean over and look down the carb,have someone pump the gas pedal ,look for gas to squirt out of the shooters,also do this after the car has been sitting over night,do not start it up ck to see if the gas is squirting from the shooters.If the gas is there from the shooters the car should start.If it still acts up I would look at the ignition,weak spark,dist,we will fix it.
 
Hello,

I just went through this on my '70 Road Runner - it turned out to be a bad brand new NAPA gold Fuel filter. It was completely blocked off right out of the box! After disconnecting all my fuel lines , blowing them out with compressed air, new fuel tank, sending unit and rubber lines, car would only run when primed. . Checked the new NAPA filter, it was a bad one. Swapped in a new one, fired right up! Check it for flow (blow through it ) and see.
Good luck.
 
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Once I get the car started by priming the carb, I'm able to drive it. It drives pretty well, but has hesitation if I goose the gas pedal.
 
If it doesn't want to start the accelerator pump isn't the problem (accelerator pumps are only a bandade for hard starting engines). A properly working carb should only need choked "no pumping", I'd check the choke to make sure it's closing all the way, check the fuel pressure, timing an float level for starters. Once started is it running rich at idle? Have you adjusted the idle screws? Just keep it in mind that you shouldn't have to pump the gas at all. Another question, what condition is the motor in? Low compression and leaky gaskets can cause headaches as well. Good luck
 
Sorry, old carb starting routine is: get in car, press gas pedal once(to prime and set choke), turn key.

X2 on check fuel filter, even if new. Quality is not what it once was.
Check inside carb for dirty air bleeds, small holes to allow air in.
 
Sorry, old carb starting routine is: get in car, press gas pedal once(to prime and set choke), turn key.

X2 on check fuel filter, even if new. Quality is not what it once was.
Check inside carb for dirty air bleeds, small holes to allow air in.
Correct if it is an electric choke but not pumping it until it starts.
 
Hmmm...I'd have to agree with the vapor lock or fuel getting boiled/peculating out of the carb. Either that or the bowls are just dumping the fuel after sitting for a while. Bad filter you would think you'd have fuel issues not only when starting but while running as well, but you never know. Choke shouldn't be a non starting issue. Big/HiPo blow through carbs like my quickfuel 950 have no chokes/butterflies and start just fine without them. Easy test would be get a jar/container, disconnect the fuel line at the carb, run it into the jar and crank the car over. Fuel coming out, carb issue...No fuel, possibly something funny with the filter. Weed that out by disconnecting the line before the filter and see what happens. At least this route will get you leveled down to what it may be before buying parts. Good luck.
 
Bradley,

I have a 70 Road Runner and I had the same problem. My car is a California car, so it has a Holley carb. In my case, I had a leaky gasket around the accelerator pump housing, so after I stopped driving the fuel would slowly drip out of the accelerator pump until the bowl was dry. Quite the fire hazard, since it must have been doing that while I was driving!

At any rate, I realize you have a Carter and not a Holley. I would try starting the car, and after running it for a few minutes, shut it down. Then check for any obvious leaks around the carb area. If this is dry, I might suggest locking the throttle wide open. When you do this, you will squirt fuel with the accelerator pump. Let it sit for a little bit for this squirt to dry and then peer down the carb and see if you can see any fuel drips.

Or, you could just bite the bullet and take the carb off and give it a quick rebuild. That's probably what it needs anyway. :eusa_think:

Good Luck.
 
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