Vapor Lock 70 Dart Swinger 340 Car

[maldridgeks]

Hello everyone. I've read through the numerous threads on vapor lock, but couldn't find the answers I'm after. Working on a 70 dart swinger 340 car with a 1979 360 in it with edelbrock intake and carb. Car exhibits signs of vaporlock. I'm weighing either an electric fuel pump or a wix fuel filter with the return line connector. Leaning toward the return line and the wix fuel filter. My gas tank doesn't have a return line adapter so I have been looking at a new sending unit that includes the return line connection. Has anyone solved their issue with this approach and if so, which sending unit did you use?

Also, has anyone tried the hot rod sleeves with success? Wondering if this is worth trying first.

Thank you.

 

[RustyRatRod]

I would actually diagnose the vapor lock first. Do you run ethanol laced gas? If so, it's certainly a possibility. One bit of hillbilly diagnosis is to clamp a lot of wooden clothespins on the metal fuel line. If that makes the issue go away, then that' what it is. The pins act as a heat sink and absorb heat off the fuel line. I've seen people just line up and leave them there. lol Looks stupid, but if that's really the problem it usually works. If that does it, you might think about also rerouting the fuel line away from heat sources or insulating it. I have the fuel line on my slant 6 insulated with foam from the pump to the carburetor. The return line is also a good idea, but pay attention to where the nipple is aimed going into the sender. They were not for solid fuel return, but for vapor return. So sending solid fuel might make it land on the sender arm and interfere with the gauge reading. You might need to braze a little longer nipple on the inside. I've had to do it before.

 

[maldridgeks]

I would actually diagnose the vapor lock first. Do you run ethanol laced gas? If so, it's certainly a possibility. One bit of hillbilly diagnosis is to clamp a lot of wooden clothespins on the metal fuel line. If that makes the issue go away, then that' what it is. The pins act as a heat sink and absorb heat off the fuel line. I've seen people just line up and leave them there. lol Looks stupid, but if that's really the problem it usually works. If that does it, you might think about also rerouting the fuel line away from heat sources or insulating it. I have the fuel line on my slant 6 insulated with foam from the pump to the carburetor. The return line is also a good idea, but pay attention to where the nipple is aimed going into the sender. They were not for solid fuel return, but for vapor return. So sending solid fuel might make it land on the sender arm and interfere with the gauge reading. You might need to braze a little longer nipple on the inside. I've had to do it before.

Thank you. Confess I assumed the wood clothes pins were akin to snipe hunting.

 

[RustyRatRod]

Thank you. Confess I assumed the wood clothes pins were akin to snipe hunting.

They actually work for diagnosis. I wouldn't leave them there. LOL

 

[Professor Fate]

If you have an original sender that still works, keep it. Most, if not all aftermarket senders are notoriously inaccurate.
I added a fuel return by adding a line to my existing tank, here:

This is the position that the factory added a line to on later tanks, so it clears all framework and trunk floor sheetmetal.
It is high enough to prevent backflow. The factory used an "L" shaped line to direct the return to the driver's side, away from the sender; so I did the same. Brazed it in place.
Now a few notes on those 3 nipple filters-
-They MUST be mounted after the fuel pump.
-If mounted vertically, the half of the filter with the third nipple must be mounted towards the top. If mounted horizontally, the nipple must point up.
-Now comes the part where I rant about (the lack of) parts quality. These filters were designed as a vapor return, not a full-fledged fuel return. As such, inside of the return nipple of the filter there is a ~1/16" restrictor orifice. On some Fram and Wix filters I have gotten lately, there is no restrictor present- if you look into the nipple and can see the filter element, there is no restrictor. You can clearly see the drilled orifice if it is present. Why is this important? Because if there is no restriction, that 1/4" line will bleed off most of your fuel pressure and volume. I spent the better part of a week of my spare time trying to track down a fuel starvation issue, when on a lark I pinched off the return line- no more problem. I removed the filter, and lo and behold- no restrictor. I checked my supply of filters and found a mixed bag of filters with and without the restrictors in place. I tried taking a pic, but my phone couldn't get a good shot down inside the 1/4" nipple; so you'll have to take my word for it. Seems although the factory had a very good reason for having them there, the parts suppliers have found yet another way to cheapen their product; so buyer beware.
To combat this, I fashioned a separate 1/16" restrictor and installed it in the return line. Now I don't need to worry about if I have a correct filter for future changes- it will work to spec if the filter doesn't have the restrictor, or just become redundant if it does.

 

[RustyRatRod]

You can also use a no weld option like this:

 

[Michael Siple]

I would actually diagnose the vapor lock first. Do you run ethanol laced gas? If so, it's certainly a possibility. One bit of hillbilly diagnosis is to clamp a lot of wooden clothespins on the metal fuel line. If that makes the issue go away, then that' what it is. The pins act as a heat sink and absorb heat off the fuel line. I've seen people just line up and leave them there. lol Looks stupid, but if that's really the problem it usually works. If that does it, you might think about also rerouting the fuel line away from heat sources or insulating it. I have the fuel line on my slant 6 insulated with foam from the pump to the carburetor. The return line is also a good idea, but pay attention to where the nipple is aimed going into the sender. They were not for solid fuel return, but for vapor return. So sending solid fuel might make it land on the sender arm and interfere with the gauge reading. You might need to braze a little longer nipple on the inside. I've had to do it before.

 

[matthon]

Return = good.

I've also had success with this, also have used it on things near headers, plug wires, speedo cable, starter wires, etc.

Pardon Our Interruption

 

[TT5.9mag]

The first thing to do is make sure there is no restriction in the suction side of the pump. So everything from the tank to the pump. If the sock on the inlet is partially clogged and causing the pump to pull a vacuum there is almost nothing you can do to solve the problem. Also edlebrock carbs are notorious for not only vapor locking but fuel percolating after shut off. A wooden or phenolic carb spacer can help tremendously.

 

[mopowers]

If the car has headers, think about insulating the metal fuel line upstream of the fuel pump next to the headers. That helped solve my vapor lock issue.

 

[DartDave73]

Insulate the carb too. I use a phenolic spacer and heat shielding on my carb to keep it cooler. Thought about making a spacer out of wood like back in the day. Maybe someday.

It's really a combination of keeping the carb cooler, and a return line (w/bypass regulator) to keep fuel constantly circulated and cooler. It doesn't hurt to have a hood scoop assembly to help push in cooler air from outside. Paid a pretty penny for the factory double-scoop, but it's worth it in the long run.

 

[maldridgeks]

If you have an original sender that still works, keep it. Most, if not all aftermarket senders are notoriously inaccurate.
I added a fuel return by adding a line to my existing tank, here:
View attachment 1716536465
This is the position that the factory added a line to on later tanks, so it clears all framework and trunk floor sheetmetal.
It is high enough to prevent backflow. The factory used an "L" shaped line to direct the return to the driver's side, away from the sender; so I did the same. Brazed it in place.
Now a few notes on those 3 nipple filters-
-They MUST be mounted after the fuel pump.
-If mounted vertically, the half of the filter with the third nipple must be mounted towards the top. If mounted horizontally, the nipple must point up.
-Now comes the part where I rant about (the lack of) parts quality. These filters were designed as a vapor return, not a full-fledged fuel return. As such, inside of the return nipple of the filter there is a ~1/16" restrictor orifice. On some Fram and Wix filters I have gotten lately, there is no restrictor present- if you look into the nipple and can see the filter element, there is no restrictor. You can clearly see the drilled orifice if it is present. Why is this important? Because if there is no restriction, that 1/4" line will bleed off most of your fuel pressure and volume. I spent the better part of a week of my spare time trying to track down a fuel starvation issue, when on a lark I pinched off the return line- no more problem. I removed the filter, and lo and behold- no restrictor. I checked my supply of filters and found a mixed bag of filters with and without the restrictors in place. I tried taking a pic, but my phone couldn't get a good shot down inside the 1/4" nipple; so you'll have to take my word for it. Seems although the factory had a very good reason for having them there, the parts suppliers have found yet another way to cheapen their product; so buyer beware.
To combat this, I fashioned a separate 1/16" restrictor and installed it in the return line. Now I don't need to worry about if I have a correct filter for future changes- it will work to spec if the filter doesn't have the restrictor, or just become redundant if it does.

This is very helpful. Thank you for sharing

 

[maldridgeks]

If the car has headers, think about insulating the metal fuel line upstream of the fuel pump next to the headers. That helped solve my vapor lock issue.

It does have headers and where the metal fuel line runs alongside them is where I've assumed a good bit of the heat is coming from. Physical access to this area is terrible - do you recall which product(s) you used?

 

[RustyRatRod]

It does have headers and where the metal fuel line runs alongside them is where I've assumed a good bit of the heat is coming from. Physical access to this area is terrible - do you recall which product(s) you used?

Can you get some pictures of this area of the fuel line in relation to the headers? That might help us come up with some viable solutions.

 

[mopowers]

It does have headers and where the metal fuel line runs alongside them is where I've assumed a good bit of the heat is coming from. Physical access to this area is terrible - do you recall which product(s) you used?

Yep - I used DEI heat sheathing: Pardon Our Interruption

Worked like a charm for me.

 

[Professor Fate]

You can also use a no weld option like this:

Never saw those before- pretty cool!

 

[maldridgeks]

Yep - I used DEI heat sheathing: Pardon Our Interruption

Worked like a charm for me.

Thank you. Will be trying this today.

 

[maldridgeks]

Can you get some pictures of this area of the fuel line in relation to the headers? That might help us come up with some viable solutions.

I have some heat sleeves I’m going to try today. Will snag some pics while I’m working on it. Thank you again for all of the suggestions.

 

[Mattax]

The silver coated fiberglass is pretty effective based on my tests using the gas grill.

This is always a difficult time of year as summer fuel isn't yet fully distributed and whatever is in the gas tank might have been purchased in December.

Keep in mind there are two issues that can occur. One is a vapor bubble in the supply line that blocks liquid fuel delivery to the bowl. It will show up as a the car going lean under moderate to heavier throttle as the bowl is not refilled to the proper level.
The other is vapor bubbles forcing fuel past the bowl's needle and seat. This overfills the bowl and causes flooding. Often worst when the car has been sitting off, or idling including stop and go traffic.

In the '60s this was addressed by making sure the fuel filter allowed bubbles to escape into the bowl. The next measure was a tiny bypass at or in the fuel pump and even relocating the filter to suction side in some cases. Finally the vapor return lines helped more. Even with all the later vapor return and capture stuff, my '85 Jeep wagon had a little bit of vapor lock after stopping for gas on hot day last month. It cleared up pretty quick but its annoying.

 

[mopowers]

Thank you. Will be trying this today.

It may not completely fix the issue, but I bet it'll at least help.

 

[maldridgeks]

It may not completely fix the issue, but I bet it'll at least help.

It did help! Now I’m researching different types of metal fuel line to replace the rubber installed by previous owner that runs from fuel pump to carb. What does everyone recommend?

 

[str12-340]

Using stock location metal line attached to frame/inner fender panel on passenger side of the engine compartment? Using headers that are too close to said metal line???

 

[maldridgeks]

Using stock location metal line attached to frame/inner fender panel on passenger side of the engine compartment? Using headers that are too close to said metal line???

Yes. We just purchased the car recently and addressing a good many issues

 

[str12-340]

sleeve the line with insulation sleeve - looks like off white canvas material sewed into a tube. Where is the fuel filter? the original metal one was at the end of the metal line, all of which was fine with exhaust manifolds... now try to stuff 4 exhaust tubes in the same space!

 

[maldridgeks]

I feel like I’m fighting a losing battle. Wrapping the lines is helping but the problem definitely still exists. After a drive and parking car for just a few minutes I can see fuel bubbling in the clear fuel filter just before the carb. Car thus far has restarted only when accelerator is floored when cranking it over. Previous owner said it died during a longer drive and they could only get it to start after letting it cool down overnight.

I have an electric fuel pump in my shop that works with existing mechanical pump. If I add that, is a return line required? Also, is there enough benefit to an in-tank pump to consider the extra investment to go that route? I do not envision converting to fuel injection either, if that impacts your thinking.

Thank you again everyone. Sure appreciate everyone’s help.