Fuel System Vapor Lock

Attached is a good write up by Summit Racing on Vapor Lock.

I cannot say that I have seen this myself, but it makes sense to me.
Vapor Lock

The neighbor sold Chapparral snowmobiles back in the early 70s. I bought a new one in 72. There were new regulations in 73 having to do with emissions and noise, so they put a whole bunch of insulation inside the hood to try to muffle some of the engine noise. Every one of those new machines that Ronnie sold came back with a vapor lock problem. He had to rip the insulation out of all of them to get the heat to dissipate through the fiberglass.

I've had arguments before about inline filters. Guys have shown me where they've mounted them vertically, right under the tank, away from the heat and they worked fine, but like I said, most of the time, somebody will cut the line down under the manifold where it's easiest to get at, then they have issues with vapor lock.

I sure hope Arnie didn't mean what he said. There are so few good Oliver mechanics left anymore and we need him here. I apologize again if anything I said had the wrong tone to it, I sure didn't mean any criticism, just my personal preference when it comes to these old fuel systems. Sincerely, sorry again.

Not normally my forum, but my Dad had a 70 oliver with side curtains and no added fuel filter. I think he had vapor lock problems on really hot days. I had a Case 350 and we did a tractor ride at 99 degrees and I had trouble with vapor lock till I took of the side curtains. That one did have a fuel filter, but not real close to the manifold. I did have down flow exhaust and that DID run close to the gas line.

THe 70 did not have the underhood muffler, but 2 straight pipes instead.

I remember reading in Oliver Heritage Magazine several years ago where a dealer had a 77 I believe it was, come in and it wouldn't run right. The changed pretty much everything but the engine block as the story was told. Finally, just on a fluke, they laid a homemade rubber fuel line outside the frame and it ran fine. It was vapor locking just from the steel line running close to the block. As I recall, they just made up a new line that ran farther away and that took care of it. Strange things happen.

I can see where any poorly running engine that is caused by fuel supply issues gets labeled as vapor lock, and I am not going to try to define vapor lock. For my stuff I have used the following guidelines;

1) Make sure that fuel lines away from the sediment bowl are sloped down hill to the fuel pump (if equipped) or to the carburetor. I do not use loops in the lines, I understand the theory of the loops, but they create places for vapors to be formed and held. The goal is to allow vapors that might form a way to travel back to the fuel tank and out the vent.

2) Although I like the look of steel and copper lines, I generally use rubber gas fuel line because it is easier to maneuver. It needs to be fuel line hose, not vent line hose.

3) If there is a place for one, I always use a sediment bowl, this gives a place to trap water and dirt plus it has a very fine screen to act as a filter. I have reworked some sediment bowl valves to remove internal flash and restrictions that might prevent full fuel flow.

4) I only use add on filters when I can place them on the outlet of a fuel pump, I have had issues with pressure drop through filters causing fuel starvation when used without a pump or on the inlet side of the pump.

5) The inside of the fuel tank has to be clean and I only use plastic fuel cans to reduce the risk of contamination into the fuel system.

There are lots of instances where not following these guidelines will work, but when I follow these guidelines I have very few issues with fuel delivery.

I can understand a case where the fuel line is close to a heat source or enclosed with a heat source, that my guidelines would not be sufficient, but I personally have not had that problem.

Randy

I do not think you said anything out of turn, I suspect he is mad at me based on my comment of 40 years and his comment since 1964.

Rich

One thing I found if using a fuel filter with gravity flow. Ones made for large lawn mowers are better than automotive ones, that are designed with an engine with a fuel pump.

I'm going to add a couple of thoughts here and later a question.
This was about 15 years ago, but I worked as a mechanic for a factory and this factory had some major flooding problems after receiving 13 inches of ran one night. One problem they had was a large outdoor pit had several million gallons of water was in it from this flood. They needed all of this water out of it, so they purchased a high-volume pump was was attached to a Briggs & Stratton twin cylinder V engine. It was the middle of summer and it was 100+ Fahrenheit every day of the week. The problem with this pump was that they would fill up the gas tank and it would run for about 30 minutes and die. Leave it set for an hour and it would start right up but again die in 30 minutes. The design of this B&S engine was that the carburetor was right between the cylinders and the gas tank itself sat right on top of the carburetor. In this temperature the gas was vapor locking. My boss called Briggs & Stratton but they were not helpful. They flat out told us that the engine was NOT vapor locking and it had to be something else. To prove my point, I took the gas tank off and moved it about 25 feet away. We put that amount of fuel line between the tank and the engine and it ran fine after that for weeks at a time. The pump would now run for hours until it ran out of gas. It was quite comical to see the gas tank further up the hill with the gasoline being fed by gravity. When the temperatures dropped a few weeks later, the pump ran fine with the tank back in place.
Now since this is being posted in the Oliver forum, I'm wondering if any of you Oliver guys ran into this vapor lock repair. I purchased a non-running Oliver 70 quite a few years ago. It was complete but had a feature added on to it and I knew immediately why somebody added on this fix. One day I saw that the front of the gas tank on this 70 had an addition on to it that was colored white. I inspected it and noticed that somebody had added on a thick sheet of asbestos to the front of the gas tank and had glued it in place. It was done very neatly and covered the entire front sheet of the tank. This was obviously installed to stop the gasoline from boiling away on a hot summer day. The 70 gas tank sits quite close to the back of the engine and I presume it probably helped quite a bit. That, and taking the side shields off.

I was raking hay with my 1550 gas on an insanely hot day one summer. Those are opened up pretty hood. The size of the engine vs the sheet metal makes things pretty open. I don't have an inline filter on it, just the stock sediment bowl and fuel line. On that particular day, gas started blowing out from under the cap. Luckily it didn't vapor lock with the stock fuel system, but the gas got so hot in the tank, it was boiling. My Whites have insulation on the front of the diesel tanks. That 1550 gas could use it.

I still feel guilty for even bringing up the inline filter and vapor lock thing. If I make everybody mad and I'm the only one left here to answer questions, the whole brand is in real trouble.