IROCtheRoad

I'm having a bit of a head scratcher > with my fuel system.

Both my original rebuilt E4ME and now rebuilt Quadrajet are not retaining fuel in their bowls over night. It takes a good 5-10 seconds of a couple of cranks to get the car to fire up. Once the car turns on I can turn it off and instantly turn it on again.

I've plugged the casting spots on both quads so I know I am not leaking fuel from there (they are also try when I've removed the carb to check).

After my build I've had to take the carb off and no fuel leaked when the fuel line was disconnected. I even moved my flexible fuel line downward at the pump and nothing dripped out.

So my question: What could be causing the fuel to drain all the way back to the tank? I'm 87% sure my factory in-tank pump is still working and obviously my block mounted pump is just 'fine.' Any ideas?

five7kid

iTrader: (14)

Which casting spots did you plug, and how did you go about it?

IROCtheRoad

I plugged the bottom 4 casting plugs with the marine rtv stuff (I honestly can't remember the name of it) that Cliff Ruggels said to use.

I cleaned the original plugs up and put the sealant on top of them and let them dry for about 2 days.

Both carburetors showed no signs of leaking in these areas which is why I don't think the carb itself is leaking and i saw no obvious signs of fuel pooling up in the intake when the carbs were off.

sonjaab

Could be you have rust in the ball discharge pump well area.
The ball will not seat properly.
This causes fuel in the bowl to leak down into the motor.

http://dyeager535.topcities.com/CCCqjetdiagram.html
Look at part # 251 on diagram

I have had this issue on on a few of my older duo-jet
2 bbl units.

To verify:
Run /drive car till hot.
Turn off motor
Remove air cleaner
Look for smoke to come out of carb throat top

If u see smoke then the carb. is leaking internally from the bowl
into the hot motor.

Electro_X

hello

i have problem like that. when i start the engine and look down the carb's fuel bowl i see light smoke coming up carb's fuel bowl.

anything i should worry about?

afremont

Since two different carburetors exhibit the same symptom, it's probably not the carbs. My guess is that the hot motor is evaporating the fuel. Maybe you could put in a carb spacer/insulator?

sonjaab

Electro........No I don't see a problem if you might see vapor smoke while the car is
running. Only while hot then engine turned off.

Afre..........If both carbs had the same issue then most likely a rotted gas line hidden in the frame rail.
This allows gas line pressure to leak down and fuel being syphoned (spl) from the
bowl.
Seen this a lot in snow and ice land rustbucket cars.

A stock hot motor shouldn't evaporate all the fuel out of the bowl IMO.
I have never seen this in a stock q-jet motor.

To check: Get a air line and hook up a blower nozzle. Wrap a rag around the blower
nozzle end and insert into the fuel filler nozzle. Apply limited air pressure and look for
leaks along the gas line or frame rail from the tank to the carb.

IROCtheRoad

I appreciate the feedback! The ball you are referring too was just fine, very clean, and I have no fumes coming out of the carb. The engine itself is running perfect (aside from overheating - but that's a fan issue).

I've traced the fuel lines all the way up to as high as you can see on the tank and they are 100% rust-free with no leaks.

Is it possible for the factory in-tank pusher to suck fuel back to the carb through the return line?

sonjaab

Have you checked the rubber lines connecting the steel fuel lines to the
tank outlets? How about the fuel line vent valve assem. located near the
rear axle? Did you check the charcoal fuel/vent/vapor canister?
Is it soaked with fuel?

Does your car have the in-tank pump and the pump on the block?
The engine mounted pump may have a internal diaphram leak and it
is leaking internally into the engine oil or the leak is small enuff to not
note/see external gas leaking/pooling either on the pump/block or ground.

BTW: Its not the pump discharge ball having a rust/corossion issue it the
well that the ball sits in in the carb body. There may be a rust burr/corrosion
crud in the well seat. A good magnifying glass is needed to see down in there.

Again smoke rising out of the carb throats on a hot turned off motor should
confirm this.
I would check the prev. posted stuff first before tearing the carb. apart.

Again my stock E4ME and choke setup takes a moment cold to fire up.
I pump the pedal twice and start the car.

afremont

That's a good point about the "vent" because it vents into the tank to relieve any vacuum on the tank. The tank and fuel absorb allot of heat when the engine is running and generate quite a suction when cooling down. If his isn't working, I wonder if it will gradually suck all the fuel from the bowl and line back to the tank.

sonjaab

Again...........If the carb float bowl is indeed dry after sitting i would also expect a
issue with the float needle and seat. You figure after shutting the car off hot the
float bowl is full so the float is held up with fuel and the float needle is seated in
its seat so in theory the gas can't leak back into the fuel line. Also there should
be pressure in the fuel line after hot running shut off.
Could be a rust burr under the needle seat where it screws into the carb. body.
It would allow the fuel to leak back into the line or carb body.

I had this issue with a old t-bird I had that had hot start flooding issues with
its motorcraft 4 bbl. carb.

Just a thought.................

paulo57509

IMO, I doubt that it's your needle and seat. If there's an issue with fuel back-draining out that way, there would be an issue with it not sealing when the engine is running = flooding.

I'd verify that the bowl is actually draining. Taking the top of the carb off with it still bolted to the manifold is one way. Run it, pull the top off and observe.

It might be that the bowl is not filling up to begin with due to the float level being adjusted too low (= lean mixture).

You get long crank times after the car sits because it needs a little richer mixture than when having just been run. After it runs a bit, it starts OK.

Just thinking out load....

IROCtheRoad

All lines are clean and dry, charcoal canister has been removed (it weighed about 20 pounds) and tank vented.

My block mounted fuel pump is a brand new Carter and I've wired a new harness/relay for the in tank pump.

I'll have to double check the ball and seat. The couple times I've had the carb apart I never took the ball out so it's possible that the seat may be rusty. I'll pull the top of the carb apart here soon and check.

But I have to go do the whole military thing for a bit so I won't be able to check for a while. Again, thanks for all the help!!

paulo57509

No, thank YOU for putting on that uniform for us.