[Jarek]

Hi
I have ’73 Challenger with 440 4-bbl Edelbrock carburetor. As I wrote few weeks ago I have problems with cold starting. When I made an investigation I noticed that even after one day of parking (without starting the engine) all fuel “escape” from fuel lines, filter and EVEN FROM CARBURETOR. When I pour gasoline into filter and indirectly into carburetor it starts without any problems.
So why all fuel VANISHING from pipes and EVAPORATE from carburetor?
Is there in fuel pomp any valve that is broken?

Thanks for help
Jarek

[dave-r]

Fuel will tend to drain back until it is at the same level as in the tank. However if you have a leak someplace it might go further back. A leak like that would be obvious though and you would be able to smell it.

Any leak would still leave fuel in the carb. The Edlebrock carb is a very good design with no gaskets below the fuel line in the carb so no leaks should happen. If the fuel is evaporating it must be due to heat soak afer you switch off.

Heat can boil the fuel out of a carb and lines so check that is not happening by running the engine up as hot as it gets and then switch off and see what happens to the fuel. If you see bubbles in the fuel line (a clear filter is good for this) or hear bubbles in the carb then that will be the problem. Doing this might bring to light what is happening as you watch.

[alex]

Sonds daft, bit smell your oil, the carb may be syphoning into the inlet, if it is it will end up in the sump, not good, not good at all (experience speaking!)

[BigB]

i have the same problem. i also had a edlebrock card. so i replaced it with a new 750 edlebrock and with the same results. If it sits over night it will be dry. i also notice that there's no fuel in my fuel line when this happens. could the fuel pump be bad? lose gas cap? i do not notice any leaks.

[dave]

Have you both got alloy inlet manifolds fitted?

If so then block off the heat riser passage in the inlet and consider fitting a plastic spacer under the carb. This is also a good idea on an iron inlet as well (worth about 10hp on a stock engine alone). This is why they invented the Thermoquad I think.

Ally conducts heat much, much better than iron. The heat from the engine after shutdown can boil the fuel away. On the Edlebrock the fuel bowls are part of the lower main housing and so heat can get to them.

It is normal for the pump to loose pressure slowly after shutting off.

You should take care to ensure your fuel lines are routed so that they are kept as cool as possible.

I also insulated mine with foam up to the pump and wrapped with tin foil. The pipe is wrapped in foil only from the pump to the carb.

Shut off your hot engines and look and listen to the lines and carb. Take the top off the carb if you like. See if the fuel boils at all. Remember that the heat is worse with the hood down so if it boils even just a little it would be worse with the hood down.

Try it and see if I am right. Tell me if I am talking rubbish.

[jarek]

Hello,
I have checked everything in fuel delivery line and there is only one problem with fuel pump.
Fuel is leaking down through pump, from filter, pipes and carburetor to fuel tank. Partial vacuum (is this correct word for low pressure of gasses in closed container?) in fuel tank is so high that all fuel is pulled down.
When I disconnected pipes problem disappeared and so it is not a problem with overheating.
And my question is - instead buying new mechanical fuel pump or repair old one , can I install electrical pump? Do you have any suggestion?
Thank you
Jarek

[dave-r]

Is the air vent in the filler cap blocked? You should not get any low pressure in the tank!!!
I have heard of fuel tanks collapsing because of that!

[alex]

Blocked tank breather sounds like part of the problem, but thay wont grain the carb

[dave-r]

Neither will a worn pump in that case then.

Stay away from electric fuel pumps Jarek. Noisey, expensive, and not needed on a street driven car.

I use a Holley mechanical pump with a Holley fuel pressure regulator and guage. Use a max of 5.5lbs of pressure with that carb of yours.