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Mopar Garage => Engine, Transmission, Rearend, & Exhaust => Topic started by: AKcharger on December 14, 2020, 06:47:19 PM

Title: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: AKcharger on December 14, 2020, 06:47:19 PM
On my '72 if the car sits more than a day the fuel bowls are empty and it takes about 3 min worth of cranking to get it to start.  now after it starts and has fuel in the system it is fine, starts right up. if it sits over night same thing.

So what ON ORDER OF LIKELY HOOD is the cause? no sign of fuel leaking anywhere

400 -  Edelbrock 750, 3 years old

Thanks!
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: Kern Dog on December 14, 2020, 07:29:16 PM
This is common in the Summer due to rapid evaporation but in the cold months? Hmmm..... :scratchchin:
Rick Ehrenberg suggested a test: Pour some gasoline into a shot glass, mark the level with a Sharpie and place it underhood near the carburetor. Do this after having the engine up to temp....then come back a day later. See how much gas evaporated from the open shot glass. If the level hasn't changed much, the problem is not evaporation.
If you have a functioning choke, does it help to use Ether?
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: AKcharger on December 14, 2020, 07:58:18 PM
Good suggestion but I've replaced the intake gasket with that "valley pan" to aboid heat, have a "cool carb" plate on it and I found evaporation after it's been running a while and engine is hot...it never does that (well not after cool carb mod and such)

yes ether or a bit of gas in car and it fires right up and runs fine
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: Kern Dog on December 14, 2020, 08:08:36 PM
I had a 360 in a Dart with a rebuilt Thermoquad. Once up to temp, it started easily and ran great. When it was cold.... :hah: crank...crank...crank...
I hooked up the choke and son of a gun....It fired up almost instantly every time. I've never been a factory stock type of guy. I've had Holleys for the most part.
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: birdsandbees on December 14, 2020, 08:42:12 PM
Check valve in pump stuck open and fuel is draining back to the tank.

Pull the line off at the carb and see if you can blow the fuel back towards the tank.
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: INTMD8 on December 14, 2020, 08:51:13 PM
Quote from: birdsandbees on December 14, 2020, 08:42:12 PM
Check valve in pump stuck open and fuel is draining back to the tank.

Pull the line off at the carb and see if you can blow the fuel back towards the tank.

If the inlet check valve in the pump was stuck open would it move any fuel to the carb?
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: birdsandbees on December 14, 2020, 09:12:03 PM
Yes... :brickwall:
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: AKcharger on December 14, 2020, 11:28:51 PM
Great info guys thanks!

Kerndog- yup has a choke, and seems to be working but when I pop the air cleaner and pump the linkage nothing come out

Birdbee- that sounds exactly like the problem! I'll try that tomorrow!!
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: INTMD8 on December 15, 2020, 09:38:59 AM
Quote from: birdsandbees on December 14, 2020, 09:12:03 PM
Yes... :brickwall:

I see,  yeah that doesn't look like it would help
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: AKcharger on December 16, 2020, 07:21:44 PM
Well it is the carb...When I disconnected the fuel line there was ample fuel still there, and did the blow check...no bypass. Also watching the jets I move the throttle and nothing, no fuel squirt at all.

So what do you guys think accelerator pump? I did not a bit of fuel residue on the cool carbĀ® plate

Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: AKcharger on December 16, 2020, 07:28:01 PM
wait wait...did google search everyone in the world has same problem, it's the accelerator pump
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: AKcharger on January 03, 2021, 03:34:27 PM
R2 accelerator pump and after 20 hours fires right up. I'll give it 48 hours next before I call it good
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: AKcharger on January 06, 2021, 08:17:56 PM
Gave it 72 hours..2 pumps on the gas peddel and fired right up so it was that little accelerator pump. Interestingly enough, it "LOOKED" fine, no rips or tears or other obvious defects
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: LaOtto70Charger on January 07, 2021, 11:59:20 AM
Good test.  My edelbrock does this all the time too. Need to check into this.
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: jerry on April 02, 2021, 01:07:32 AM
my 69 A-12 car has been like that for 30 years
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: Kern Dog on April 02, 2021, 03:47:07 AM
Quote from: AKcharger on January 06, 2021, 08:17:56 PM
Gave it 72 hours..2 pumps on the gas peddel and fired right up so it was that little accelerator pump. Interestingly enough, it "LOOKED" fine, no rips or tears or other obvious defects
If I recall, the seal on the accelerator pump shrinks and loses it's seal in the bore that it travels in.
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: Nacho-RT74 on April 02, 2021, 06:45:10 AM
If it was a TQ the first guess from me it was to be... cracked fuel bowl or cracked epoxy at fuel wells at bowl.

Really common failure
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: AKcharger on April 02, 2021, 11:52:11 AM
Well, problem back. Same thing, perhaps the accell pump went bad hat fast? I got an original Holley to on the '70, when I get it on I'll cross-cannibalize the eddy carb over to the '72
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: Kern Dog on April 02, 2021, 02:27:40 PM
Oh no...that sucks!
Ethanol gas evaporates faster than pure petroleum gasoline. All carburetors that I have seen have vents that are open to the inside of the air cleaner. This means that they can lose vapor and eventually the "fluid" of gas. The hotter the weather, the faster they will evaporate.
Also....Holley carburetors have the accelerator pumps at the bottom of the float bowl so even if the primary jets aren't swimming in fuel, the accelerator pump can still provide a pump shot. Carter and Edelbrock carbs need more fuel in the bowls before the accelerator pump will work as compared to a Holley. Sometimes with a Holley, you can get the engine to sputter long enough while cranking on just a few acc pump shots for the fuel pump to fill the bowl.
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: c00nhunterjoe on April 02, 2021, 03:36:50 PM
Quote from: Kern Dog on April 02, 2021, 02:27:40 PM
Oh no...that sucks!
Ethanol gas evaporates faster than pure petroleum gasoline. All carburetors that I have seen have vents that are open to the inside of the air cleaner. This means that they can lose vapor and eventually the "fluid" of gas. The hotter the weather, the faster they will evaporate.
Also....Holley carburetors have the accelerator pumps at the bottom of the float bowl so even if the primary jets aren't swimming in fuel, the accelerator pump can still provide a pump shot. Carter and Edelbrock carbs need more fuel in the bowls before the accelerator pump will work as compared to a Holley. Sometimes with a Holley, you can get the engine to sputter long enough while cranking on just a few acc pump shots for the fuel pump to fill the bowl.

:iagree:  any carter/eddy setup i have had my hands on with a mechanical fuel pump will need some cranking to refill the carb after the fuel has evaporated after a few days of sitting. If this is happening overnight or in 1-2 days of sitting, then there may be other issues. But a week is normal in my opinion, especially as the temps increase.
Title: Re: Carb/Fuel line 'looses prime" takes forever to crank & start after sitting
Post by: flyinlow on April 02, 2021, 08:05:12 PM
I installed a Carter electric pump back near the gas tank . Only use it to refill the carb after a longer sit. Turn it on and it busses away for 5-10 seconds then quits when the carb is full. Turn it off , start the car with normal cranking. The engine driven pump with suck thru it. The electric pump will push thru the engine driven pump with the engine off.

It only puts out about 4psi , but it might get you home sometime if the engine driven pump fails, depending on whats wrong with it.

Holley carbs evaporate to empty also , it just takes longer.

The electricity in a Tesla will evaporate eventually if you don't keep toping it off.