vapor lock

[67 ragtop]

I am having vapor lock this year and it is not even summer yet. This is on my 67 Sprot Fury with a 383 2bbl. I am planning on installing a Carter electric Fuel pump back at the tank and a 33040 Wix fuel filter with vapor return. Has anyone used one of the existing vent lines for returning the vapors from the filter to the tank? I will use Nicor tubing as my return line.
Yesterday it was 85 degrees and the car would stall at Idle at lights. It would then take me flooring the pedal and a long crank to get it started. The clear fuel filter I put on for troubleshooting would show no or little fuel in the line. I have had this problem before and just changed the fuel pump, but I shouldn't need to change fuel pumps every year. I am going to use the carter pump as it is ‎Gerotor design and will suck fuel vs the Edelbrock which is a pusher design. I am also going to remove and block off the mechanical fuel pump. I was goin to use it after the electric tank but if the diaphragm ruptures it will flood the crankcase with fuel.
Any help will be appreciated.

 

[Big_John]

When you changed the pump, did you check the length of the pump push rod?

 

[commando1]

Has the fuel line routing from the fuel pump to the carb still in its factory location or has it been modified over the years? I have seen too many times seen the gas filter literally lieing on the exhaust manifold.

 

[Just Carbs]

Yes, the vapor return filter using the vent return line has always solved my vapor lock problems on Mopar's. Never needed anything other than the stock pump.
I use vented tank filler caps so the tank doesn't get sucked into a collapsed mess.

 

[Sixpactogo]

I am having vapor lock this year and it is not even summer yet. This is on my 67 Sprot Fury with a 383 2bbl. I am planning on installing a Carter electric Fuel pump back at the tank and a 33040 Wix fuel filter with vapor return. Has anyone used one of the existing vent lines for returning the vapors from the filter to the tank? I will use Nicor tubing as my return line.
Yesterday it was 85 degrees and the car would stall at Idle at lights. It would then take me flooring the pedal and a long crank to get it started. The clear fuel filter I put on for troubleshooting would show no or little fuel in the line. I have had this problem before and just changed the fuel pump, but I shouldn't need to change fuel pumps every year. I am going to use the carter pump as it is ‎Gerotor design and will suck fuel vs the Edelbrock which is a pusher design. I am also going to remove and block off the mechanical fuel pump. I was goin to use it after the electric tank but if the diaphragm ruptures it will flood the crankcase with fuel.
Any help will be appreciated.

I'm not familiar with that Wix 33040 filter. Does it have an orifice in the return nipple to shunt the return back to the tank like the Mopar separator does? If not, you may be sending too much fuel back to the tank and starve your engine. Another thing you may consider is pulling your send unit and solder in a 1/4" return like the factory did with their 3/8" sender with return. I know there are a few folks that have done it that way rather than messing with the vent lines.
If it were me, I would forgo the electric pump and used the tried and true Mopar method rather than try and reinvent the wheel so to speak. I remember my brothers 68 Charger 383 car vapor locked quite often on hot days until we swapped in the sender, lines and separator from a wrecked car. He never had the problem again.
Are you certain you don't have a partially plugged sock on you sender or a fuel filter blockage?

 

[FURYGT]

I agree with others that there are things to look into before you consider an electric fuel pump and this is coming from someone who does have an electric fuel pump in one of my C Bodies.

Have you tried removing the fuel filter and inspecting it? I have friends that have had the clear plastic filter develop a hairline crack or had part of the filter break down and cause a restriction.

Maybe you need an insulated spacer under the carburetor or need to block off the intake manifold heat crossover.

If you insist on using an electric fuel pump you will also need a fuel pressure regulator and gauge unless the Carter pump that you refer to has an internal pressure regulator that is set within factory specifications.

Good luck.

 

[CBODY67]

Chrysler did use an electric pump on some Imperials. '73 with CA Emissions, I believe. It was at the tank, in a fuel line loop between the sending unit and the normal lines, from the way it looked in the FSM.

The problem you have is probably due to the winter gas (YES, that IS a thing) in the car and in most fuel tanks in the region. This time of the year, it can happen to any gasoline-powered vehicle. NOT a design issue with your car per se, which is designed about the gas we had in the middle 1960s and the seasonal blends back then.

Seems to me that ALL electric pumps are both "pushers" and "pullers". In order to "push", a low pressure situation must exist to "pull" the fuel to it before it can push it? Just like the mechanical pump does, just using electrons to power the electric pump.

As Chrysler did not usually use a factory return line-style fuel pump, the "filter-separator" is the next best thing. Of course, some different fuel lines might be needed to make it work.

Keep us posted on your progress,
CBODY67

 

[67 ragtop]

When you changed the pump, did you check the length of the pump push rod?

No I did not. I didn't know to do it. where do I find the spec? I looked in the service manual today and could not locate it. But I am blind in one eye and can't see out of the other. Fords do not have a measurement for that and that is the primary carbureted vehicles I have worked on.

 

[67 ragtop]

I'm not familiar with that Wix 33040 filter. Does it have an orifice in the return nipple to shunt the return back to the tank like the Mopar separator does? If not, you may be sending too much fuel back to the tank and starve your engine. Another thing you may consider is pulling your send unit and solder in a 1/4" return like the factory did with their 3/8" sender with return. I know there are a few folks that have done it that way rather than messing with the vent lines.
If it were me, I would forgo the electric pump and used the tried and true Mopar method rather than try and reinvent the wheel so to speak. I remember my brothers 68 Charger 383 car vapor locked quite often on hot days until we swapped in the sender, lines and separator from a wrecked car. He never had the problem again.
Are you certain you don't have a partially plugged sock on you sender or a fuel filter blockage?

Yes the 33040 has an Orifice in the return system and is the filter that Uncle Tony recommends. I am sure the sock is not clogged as I replace the sending unit and tank last summer. I may have had an issue with the gas cap as I was not sure if it had a vented or non vented cap. I put a non vented cap on it. After a search today I found it should have a vented cap. I have one but it leaked fuel. The search today showed it should be a vented surge resistant cap. on the convertible. Thank you for your reply

 

[CBODY67]

A non-vented cap can cause fuel starvation as there is a vacuum in the tank, from suction of the fuel pump.

Get a new fuel pump pushrod from a reputable vendor. Hopefully with hardened ends. No specs of that length, usually, but might be in the RockAuto catalog description specs for such.

CBODY67

 

[cbarge]

85 degrees in Texas..I am jealous, lol
I am assuming it is hot/ warm all year round and the choke never gets used.
If so, I recommend pulling the intake, get a new turkey pan intake gasket and block off the heat crossover ports.
Also make a carb spacer half inch thick from plywood
Doing both will drop the ambient temperature at the base of the carb by 100 degrees!
That alone reduces the chances of vapor lock greatly.
The other suggestion mentioned are also good ideas and can be implemented with my trick.
Both cars are 383 and both start first twist of key in hot humid weather.
No stalling or flooring the gas.
Both run stock fuel pumps,lines and filters.

 

[cbarge]

Pic of the intake turkey pan showing blocked heat crossovers, insulation wrapped in tin foil, abd sections of the pan painted to match engine.
I cut pieces of old pan to match the ports and used high heat silicone.
Since I live in the Great White North, both cars run electric chokes.
Others can use a manusl choke cable from any parts jobber.

 

[Big_John]

No I did not. I didn't know to do it. where do I find the spec? I looked in the service manual today and could not locate it. But I am blind in one eye and can't see out of the other. Fords do not have a measurement for that and that is the primary carbureted vehicles I have worked on.

It's become a common failure point. Once the pushrod starts to wear, it wears very fast as it goes from the case hardened outside to the non hardened inside. (think Tootsie Roll Pop).

You won't find the length in the FSM. It should measure 3.220" in length.

You have to pull the pump and then the allen headed plug to remove.

Typical wear, pic stolen from a @Toolmanmike post.

 

[Ripinator]

It's become a common failure point. Once the pushrod starts to wear, it wears very fast as it goes from the case hardened outside to the non hardened inside. (think Tootsie Roll Pop).

You won't find the length in the FSM. It should measure 3.220" in length.

You have to pull the pump and then the allen headed plug to remove.

Typical wear, pic stolen from a @Toolmanmike post.

View attachment 647836

You can get a new fuel pump pushrod here:

Fuel Pump Pushrods-store.440source.com

 

[It's better in a letter]

I will attempt to correct misconceptions about "vapor lock". If liquid fuel is getting to the pump and it is capable of pumping the liquid, then "vapor lock" cannot occur. Vapor lock only occurs when there is "vapor" in the suction line from the tank. The pump cannot pump vapor! Therefore, it will not move the vapor through the system until liquid is again at the tank side of the pump. If vapor does develop in the line beyond the pump it will be quickly pushed into the carburetor. The only cure for "vapor lock" is to ensure that fuel cannot vaporize in the line from the tank!

 

[Sixpactogo]

I will attempt to correct misconceptions about "vapor lock". If liquid fuel is getting to the pump and it is capable of pumping the liquid, then "vapor lock" cannot occur. Vapor lock only occurs when there is "vapor" in the suction line from the tank. The pump cannot pump vapor! Therefore, it will not move the vapor through the system until liquid is again at the tank side of the pump. If vapor does develop in the line beyond the pump it will be quickly pushed into the carburetor. The only cure for "vapor lock" is to ensure that fuel cannot vaporize in the line from the tank!

IMO, I believe the vapor lock occurs in the pump itself from heat of the engine migrating to the pump when shut down. I believe that is why Mopar created the vapor separator and installed it after the pump to send the vapor back to the tank. It is the only theory that makes sense to me since the incoming fuel line is at least a few inches away from the heat source.

 

[watchfatha]

I would make sure that the rubber fuel hose connection at the tank is good. If it is cracked or porous the fuel pump (which is PULLING vacuum at that point) can suck in air and give some of the symptoms you identify. Same goes for any rubber fuel line from the tank line there it sits up front with a rubber hose to the fuel pump (also suction side, same issue). Before I did anything else, I'd replace those hoses.
Good luck

 

[michiganhotrod1]

Look for the rubber connector line where the steel fuel line crosses intothe frame by the transmission. It is kind of hidden and often overlooked.
Mark

 

[detmatt]

I would put all my money on a worn out pushrod in this case.

 

[It's better in a letter]

I agree that vapor forming in the suction side of the pump itself will cause a problem because the overriding fact is that the pump can't move it on. Other than that addition I stand by my explanation.