Running out of gas with a full tank

chope97

chope97

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Twice in the last month my car has run out of gas after driving around for a couple of hours. It starts fine and I can drive it around for a while but then it will start to loose power especially after I stop at a store go in for maybe 30 minutes. I come out and it might be a little hard to start. Then I get it started and start driving about 20 feet and the car looses power. Yesterday I drifted it back into a parking spot. I opened the hood and sprayed starter fluid down the carbs. The car runs for a a few seconds. I took a fuel hose a loose and no gas came out. The gas tank is full. I checked all the fuel lines hose clamps. I did find one clamp that was not tight. I kept cranking the car until I see gas coming out of the disconnected hose. I reconnect the hose and eventually the car starts and stays running. Everything is back to normal and I drive home. This was a very hot day. My fuel pump is new. Could this be vapor lock because of the heat? Could the loose hose clamp be causing the problem? I am thinking of switching to an electric fuel pump.
 
I have discovered that “new” doesn’t always mean “functional”. If it’s that new maybe get another one during the return period, but the lack of fuel coming out certainly points to an intermittently functioning fuel pump.
 
It sounds like one or more of these:
Plugged filter
Plugged or collapsing hose
Sediment in the pick-up or float assembly
weak fuel pump

Since you have already found that the pump is not delivering a stream when cranking I suspect the pump.

Check your fuel pump volume by getting a clear bottle and cranking the engine allowing fuel to pump into the container. You should have a steady stream of fuel.
 
Looks like your weather has been in the mid 90s. After sitting 30 minutes and not running for long after restarting, I would suspect vapor lock.
 
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My 2 cents…

To minimize vapor lock, make sure NONE of your fuel line is higher than the fuel bowl inlet. That is a prime setup to create vapor lock. It also helps to route your fuel line away from hot spots and direct heat sources.
I once had a VW where the gas tank vent was plugged. It would run for a while and then die due to the vacuum created in the fuel tank as fuel was being used!

And FWIW… while we are talking about typical problems, I see most Weber carb conversions have an open half-inch hole at the front of the carb. I believe Weber already added redundant internal vents elsewhere, meaning that big front hole is completely unnecessary. If you plug that half-inch hole with a rubber plug, you will never have empty float bowls again. My car can sit for months and fires right up with no priming.

I think that stalling after a few minutes of driving is also a symptom of coil overheating or condenser failure?
Or perhaps float is sticking and is fuel bowl empty?
 
Ditto, here in New England. So I have researched and here is my conclusion.
Ethanol gas has a lower boiling point about 175 degrees than Non Ethanol gas 300 degrees.
I installed a clear fuel filter and you can see the gas bubbling and vaporizing causing steady performance issues.
Super hot and humid days my car was doing the same thing.
I run Weber's and routed the fuel lines like the manual shows. Away from the radiator hoses.
Ethanol gas and my negative issues go away.
Electric fuel pump is what the old car guys use on built engines. Constant pressure. 3-5 lbs.
 
restart said:
My 2 cents…

To minimize vapor lock, make sure NONE of your fuel line is higher than the fuel bowl inlet. That is a prime setup to create vapor lock. It also helps to route your fuel line away from hot spots and direct heat sources.
I once had a VW where the gas tank vent was plugged. It would run for a while and then die due to the vacuum created in the fuel tank as fuel was being used!

And FWIW… while we are talking about typical problems, I see most Weber carb conversions have an open half-inch hole at the front of the carb. I believe Weber already added redundant internal vents elsewhere, meaning that big front hole is completely unnecessary. If you plug that half-inch hole with a rubber plug, you will never have empty float bowls again. My car can sit for months and fires right up with no priming.

I think that stalling after a few minutes of driving is also a symptom of coil overheating or condenser failure?
Or perhaps float is sticking and is fuel bowl empty?
Click to expand...
Don't know about other carbs, but I'm pretty sure that hole in the front of the DCOEs needs to allow airflow. A couple of years ago I ran into Amy Lester (@coupelady) at the Highlands Motoring Festival and her car was stumbling on the drive up. I took a look at her carbs and found that she had little filters in those openings, and in the process of cleaning up her engine bay, she had turned a couple of them sideways so that they blocked most of the opening. We returned them to the proper orientation and the car ran fine. If those openings were redundant, this would not have worked.
 
I just noticed that the fuel filter is sitting right above the valve cover. I am sure it puts out plenty of heat and acts like a heat source for the plastic fuel filter. i am going to reroute the filter and hose away from the valve cover as much as possible maybe put the filter on the firewall.
 
Is it only the early cars (with Webers) that do not allow the electric condensor fan to run after shut down have the vapor lock problem?
I suspect since they do not run a fan after shutdown that the heat is not removed or atleast reduced under the hood.
I do plan to change radiators and add the thermostat along with a better electric fan.
I believe this will certainly help.
 
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Ohmess said:
Don't know about other carbs, but I'm pretty sure that hole in the front of the DCOEs needs to allow airflow. A couple of years ago I ran into Amy Lester (@coupelady) at the Highlands Motoring Festival and her car was stumbling on the drive up. I took a look at her carbs and found that she had little filters in those openings, and in the process of cleaning up her engine bay, she had turned a couple of them sideways so that they blocked most of the opening. We returned them to the proper orientation and the car ran fine. If those openings were redundant, this would not have worked.
Click to expand...

Interesting!
I’m just a creative hack shade tree mechanic doing this because I can’t afford a real mechanic.
The car runs great and starts right up after months of sitting.

I’m understanding that plugging those front ports keeps modern fuel from boiling away during a hot soak and evaporating over the long term.

So what possible reasons for the car to run properly with those holes plugged?
Could it mean the float bowl is finding an alternate "sneak path" for air-
Like:
-An open or disconnected vapor line to the charcoal canister
-micro-gaps around the top-cover gasket,
-clearances around the throttle shafts,
-clearances around the choke mechanism shafts,
-minor casting porosities or
-internal passageways
-unsealed auxiliary venturi fits
-internal air-bleed cross-drillings

allowing air to bypass the closed-off front port?

And please,
Any thoughts on the fuel lines being running slightly higher than the carb inlet and facilitating a vapor lock?? I see a lot of fuel filters installed in the engine bay with the lines running slightly higher than said carb inlet?

Cheers!
 
Dan Wood said:
Is it only the early cars (with Webers) that do not allow the electric condensor fan to run after shut down have the vapor lock problem?
I suspect since they do not run a fan after shutdown that the heat is not removed or atleast reduced under the hood.
I do plan to change radiators and add the thermostat along with a better electric fan.
I believe this will certainly help.
Click to expand...
That fan only runs if car is on, the relay was added in MY74 coupes but can be added with a diode as Don has done. All Webers have this issue and a phenolic spacer under the carb supposedly helps.
 
restart said:
Interesting!
I’m just a creative hack shade tree mechanic doing this because I can’t afford a real mechanic.
The car runs great and starts right up after months of sitting.

I’m understanding that plugging those front ports keeps modern fuel from boiling away during a hot soak and evaporating over the long term.

So what possible reasons for the car to run properly with those holes plugged?
Could it mean the float bowl is finding an alternate "sneak path" for air-
Like:
-An open or disconnected vapor line to the charcoal canister
-micro-gaps around the top-cover gasket,
-clearances around the throttle shafts,
-clearances around the choke mechanism shafts,
-minor casting porosities or
-internal passageways
-unsealed auxiliary venturi fits
-internal air-bleed cross-drillings

allowing air to bypass the closed-off front port?

And please,
Any thoughts on the fuel lines being running slightly higher than the carb inlet and facilitating a vapor lock?? I see a lot of fuel filters installed in the engine bay with the lines running slightly higher than said carb inlet?

Cheers!
Click to expand...
We appear to be talking about different carburetors. A Triple Weber DCOE setup will not be connected to the charcoal canister. As to the other items you list, I would consider all of them to be vacuum leaks to be identified and fixed. Then again, I'm pretty sure I have a small vacuum leak I need to track down on my car as I'm sitting here typing this.
 
Oh! Yes!
I’m talking about dual 32/36.
Duh! Sorry for the confusion. Agreed on the vacuum leaks. Just idle speculation, pun intended, and trying to determine why it works and how big those ‘leaks’ need to be. Etc.
I think I first discovered that plug the hole idesa on a Ford Capri forum.

It would be interesting to have a bigger data pool. I just stuck a couple of rubber vacuum caps in the holes as an experiment last year. And really, the car fired in two turns in spring!

FTR. I do have a 3 psi electric fuel pump.
 
One place to start is to remove the air cleaner, and cup your hands over each carb in turn. If your idle doesn't change when you cover one of the carbs, you have started to identify where your vacuum leak may be.
 
I was having a vapor lock problem. I proved it by buying a bottled water and pouring some water over the fuel pump and over the fuel filter to cool down the fuel vapor. It fixed the problem. My issue was that my new Pierburg fuel pump was faulty.

- Steve
 
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