Help Vapor lock

[NP435]

So after a few years with my current CJ7 the dreaded vapor lock has reared its head, so far the fuel lines are insulated. My thought now is perhaps a ball valve on the hot water hose that passes hot coolant in the manifold for the frozen cold season. Shut off in may open in sept. Thoughts anyone? The rich condition at 8000 ft and up is another thing. My carb is a 2150 motor craft that works pretty well. I have no idea where to go with jetting if jets are even available?

 

[Patrick]

Back in my carburetor days, I solved this issue with a very low pressure (3.5 psi) high volume electric fuel pump placed within two feet of the fuel tank. Fuel in liquid state will always be present at the fuel pump inlet, positively eliminating vapor lock.

 

[007]

I fought with vapor lock for quite awhile. Never had a problem where I lived at the time (400’) but in Colorado I’d have issues as low as 6000’.

i tried electric pumps with bypass regulators. I’d run about 15-20lbs high flow and send 5 or whatever to my 2100. I tried insulation. I tried foil. I tried running a gallon of diesel with 14gal of gas to raise boiling point. Nothing mattered. Once the Snipers were released late 16 early 17 I went that route and the problem was over…at least in Colorado.

Now I live in NW Nevada and have been driving my Jeep to work about 30 mins away. It’s about 5000-5500’ here and 5-15% humidity and when the temp is over 92-93 degrees I can’t make it home without vapor lock about a mile out.

It seems that there are an infinite number of factors that come into play when dealing with vapor lock. But when I had a carburetor and again now, I can tell you just by priming the pump if it’s going to start or not. I don’t know if it is some inability to push fuel through the vapor locked area, or if the vapor lock is actually happening between the pump in the tank. Either way it’s an issue. The only thing I’m sure of is that there’s probably a different reason for every person who experiences it.

 

[NP435]

I fought with vapor lock for quite awhile. Never had a problem where I lived at the time (400’) but in Colorado I’d have issues as low as 6000’.

i tried electric pumps with bypass regulators. I’d run about 15-20lbs high flow and send 5 or whatever to my 2100. I tried insulation. I tried foil. I tried running a gallon of diesel with 14gal of gas to raise boiling point. Nothing mattered. Once the Snipers were released late 16 early 17 I went that route and the problem was over…at least in Colorado.

Now I live in NW Nevada and have been driving my Jeep to work about 30 mins away. It’s about 5000-5500’ here and 5-15% humidity and when the temp is over 92-93 degrees I can’t make it home without vapor lock about a mile out.

It seems that there are an infinite number of factors that come into play when dealing with vapor lock. But when I had a carburetor and again now, I can tell you just by priming the pump if it’s going to start or not. I don’t know if it is some inability to push fuel through the vapor locked area, or if the vapor lock is actually happening between the pump in the tank. Either way it’s an issue. The only thing I’m sure of is that there’s probably a different reason for every person who experiences it.

My last CJ had the same carb and never any trouble. This one may cause me to pull hair, starting with insulation. I have almost zero interest in injection, money and my pockets are pre empty

 

[007]

Well part of what I’m saying is that even EFI isn’t a magic bullet. I always had mixed emotions about insulation. It keeps the heat away unless it’s keeping it “in” so it’s a tough call. A stock 6 has the fuel lines on the passenger side so one would think that would help. The V8s ran driver side and I moved mine over. Helped a bit. Good low octane fuel helps.

One thing to try that I didn’t is mounting a fuel can on the bumper or sit one on passenger floor. Run a fuel line out of that and see what happens. If it vapor locks you’ll know the issue is under the hood if it doesn’t you’ll know it isn’t.

 

[NP435]

Well part of what I’m saying is that even EFI isn’t a magic bullet. I always had mixed emotions about insulation. It keeps the heat away unless it’s keeping it “in” so it’s a tough call. A stock 6 has the fuel lines on the passenger side so one would think that would help. The V8s ran driver side and I moved mine over. Helped a bit. Good low octane fuel helps.

One thing to try that I didn’t is mounting a fuel can on the bumper or sit one on passenger floor. Run a fuel line out of that and see what happens. If it vapor locks you’ll know the issue is under the hood if it doesn’t you’ll know it isn’t.

One thing I have thought about is the intake manifold its self, this is a Clifford, the other CJ had a stock intake manifold and unknown header exhaust. I know I have more flow than the carb can handle. I wonder if this enhances the vapor lock? Thanks for the ideas.

 

[007]

I was just at the gas station here in Nevada, and noticed that I have one close by that sells ethanol free gasoline. So I did a search and found this interesting tidbit.

https://www.grabner-instruments.com...revision=00f78dc8-029e-4481-ba85-e640bdc7e338

 

[Belizean]

An interesting read for sure

 

[BrockGrimes]

My last CJ had the same carb and never any trouble. This one may cause me to pull hair, starting with insulation. I have almost zero interest in injection, money and my pockets are pre empty

You can add throttle body injection for about $300 if you're willing to do a little work. See info about it in my post here: https://jeep-cj.com/community/threads/useful-info-thought-id-share.665/

Another example: https://www.jeepforum.com/forum/f12/junkyard-tbi-write-up-1066016/
There are more.

Basically a TBI out of a 80's like a '89 4.3L S10 or s10 blazer. The ECU usually always listed (1227747 or 1228746). The harness was the same as the others. The best $300 I ever spent on my Jeep (includes everything).

Snag the Throttle body and rebuilt it (takes like 5min), snag the computer. Affordable Fuel Injection (AFI) grab the harness and maybe a reprogrammed chip. Sensors and O2 bung (Holley). Super easy and runs better that the carb ever did.

 

[cglax6]

Well part of what I’m saying is that even EFI isn’t a magic bullet. I always had mixed emotions about insulation. It keeps the heat away unless it’s keeping it “in” so it’s a tough call. A stock 6 has the fuel lines on the passenger side so one would think that would help. The V8s ran driver side and I moved mine over. Helped a bit. Good low octane fuel helps.

One thing to try that I didn’t is mounting a fuel can on the bumper or sit one on passenger floor. Run a fuel line out of that and see what happens. If it vapor locks you’ll know the issue is under the hood if it doesn’t you’ll know it isn’t.

Do you have an inline fuel pump? I've heard a lot of issues with inline pumps and CJs because it's tough to keep them lower than the fuel tank so it can push instead of pull fuel. For that reason I got one of the Holley Retrofit in-tank pumps for my Sniper and it's awesome. It's also internally regulated, so no need for a return line. It cost a bit more, but definitely worth it.

 

[007]

Do you have an inline fuel pump? I've heard a lot of issues with inline pumps and CJs because it's tough to keep them lower than the fuel tank so it can push instead of pull fuel. For that reason I got one of the Holley Retrofit in-tank pumps for my Sniper and it's awesome. It's also internally regulated, so no need for a return line. It cost a bit more, but definitely worth it.

I do yes. I'm hoping to swap out the the tank this winter to the Sniper one and do a active/passive pump setup where it runs from the in-tank unless there's a failure, then I can cut over to the frame mounted one.

I've resisted this for quite awhile. I have a 77 so it has the stupid 76/77 tank which is different from 78 and on, but I'll make it work.

 

[Lumpy Grits]

Move your fuel filter away from the exhaust.
Get rid of the insulation on the fuel lines.
Use the minimum amount of rubber hose. Use steel as much as you can.
Gary

 

[NP435]

Thanks for all the advice.

 

[Patrick]

Here’s a little more practical info with regards to vapor lock. For the most part, vapor lock takes place at the fuel pump and inlet side. Due to heat build up, and in some cases combined with poor fuel flow, the fuel pump is presented with an air bubble at the inlet. It rapidly loses its prime and the carburetor is starved of fuel. Quenching the fuel pump (not the carburetor) with a cold beer will condense the fuel back to liquid form and you are back to having fun.

So, the thing is, how’s this problem solved? It takes an educated approach to solve it. One thing to think about is the fuel pump itself. If you have a low quality pump, or one that is on its last leg, vapor lock will show up at a much earlier heat stage. Consider an expensive high quality fuel pump. This could effectively cure the vapor lock woes, and will pay for itself. Good luck.

 

[NP435]

Here’s a little more practical info with regards to vapor lock. For the most part, vapor lock takes place at the fuel pump and inlet side. Due to heat build up, and in some cases combined with poor fuel flow, the fuel pump is presented with an air bubble at the inlet. It rapidly loses its prime and the carburetor is starved of fuel. Quenching the fuel pump (not the carburetor) with a cold beer will condense the fuel back to liquid form and you are back to having fun.

So, the thing is, how’s this problem solved? It takes an educated approach to solve it. One thing to think about is the fuel pump itself. If you have a low quality pump, or one that is on its last leg, vapor lock will show up at a much earlier heat stage. Consider an expensive high quality fuel pump. This could effectively cure the vapor lock woes, and will pay for itself. Good luck.

That makes sense, I mostly cured the trouble with insulation, and when its cooler and the time is there Im looking to reroute the lines under the radiator then up to the filter/presure regulator. My Limited testing today went very well. Restarted pretty quick. Now to find jets for the 2150 that work from 4800 ft to 12k or so.

 

[JohnKcj5]

Do you have a fuel filter that has the output for the tank return line? You have a line running from the small output to the tank and the small output is facing upwards, right? I'm asking because a lot of people install the cheap autozone filter that has one output to the carb.

 

[NP435]

Do you have a fuel filter that has the output for the tank return line? You have a line running from the small output to the tank and the small output is facing upwards, right? I'm asking because a lot of people install the cheap autozone filter that has one output to the carb.

The filter is one in one out no return to tank.