The Stovebolt Site Forums The Shop Area Engine Shop Vapor Lock?

I need some help, I just got my 55 car with the original 235 6cyl. rebuilt and back on the road 4 weeks ago. This afternoon, I started it and headed home from work, on the way it died, I was doing 60 on the interstate and it sputterd a few times then died, I coasted off to a gas station and everything seemed fine. My glass bowl fuel filter seemed low of gas, tank was full, I turned over the engine and the bowl started filling up and pretty soon it started. Is this vapor lock? What can I do to cure it? I live in South Louisiana so we have some hot days.

Check to make sure you don't have a chunk of crud restricting your fuel line somewhere. You could be having flow rate problems. Also make sure your tank vent is working. Vapor lock is unlikely at high speed, it usually happens when you shut the car off and the fuel lines get hot. Make sure your fuel lines don't run near any exhaust components just in case though.

Thanks, good point, I did have some crud in the glass fuel bowl, my fuel line from the pump to the tank is not in the best of shape. I'll be ordering a new one tomorrow.

With all the miles I have put on Chevy sixes, I have never had one vapor lock. I've worn out 7 of them, and it does get hot in Kansas. The **** v-8 owner of the 50's couldnt say that. Vapor lock is essentially when the gas boils in the fuel line, if you cool the line it stops the boiling and the gaseous fuel reverts to liquid, allowing it to flow again. If you really want to cure a vehicle that vapor locks, put in an electric fuel pump.

Well, it happened again. I have an entire new fuel system, new lines and put the sock back in the tank. I was driving down the highway yesterday after running some errands and the carb ran out of gas. I looked under the hood and my glass bowl fuel filter was empty again. I loosened the glass bowl and some pressure was released and it started filling with gas. I got back in the car and after filling the carb it started. I left my gas cap loose to try and help and drove off. I went about 8 miles and it died again. I raised the hood and the glass fuel bowl had gas in it, I again loosened it and it seemed to have some pressure but not as apparent as before. I noticed some black gunk seeping from the carb gasket. Is my gas in the carb boiling? My heat risor is not stuck, but the spring doesn't hold it close when the car is hot, when I hit the gas the exhaust closes the flapper but when it's idling it allows the flapper to remain open just like when the car is cold, is this normal or should the spring hold the flapper open when cold and close when hot. I wired it shut last night and will cruise around this afternoon and see what happens. My daily driver isn't starting off to dependable.

If you're going to do anything to the heat riser valve, wire it open to let all the exhaust pass through. Also, do you have a spacer under the carb? They help keep the carb from getting too hot.

Check the needle and seat in the carb. Mine once came partially unscrewed and jammed against the float. (Rochester BC one bbl, hot air choke) This prevented much gas from getting into the carb, so at highway speeds the carb went dry and the engine died.

Get a new heat riser spring, make sure the spacer is under the carb, and go through the carb for loose parts, plugged passages or bad gaskets.

good luck

chip

My car died again yesterday. I have the heat riser wired shut (Heat Off). Not only is the carb running out of gas the glass fuel bowl is also. As soon as I loosen the glass bowl it starts filling with gas, so I now it has pressure on it. After this the car will start and run for a few more miles unless I let it cool off. My pump to glass bowl filter fuel line runs right over the thermostat housing and close to the radiator, this is the stock location, I replaced the steel line with a stainless one when I rebuilt the engine. I insulated this line and put clothes pins on it. I'll see if this helps. How does an electric fuel pump cure vapor lock, I may need to install one.

Double, double check the heat riser. The weight needs to be angled down instead of horizontal. The riser is normally open until it heats up then it closes.

An electric fuel pump mounted at the tank will not get hot and will always push fuel through the system at a constant pressure. I'm trying to think of what else could be causing your problem. What kind of fittings are you using on the fuel line? Double flares are best, compression fittings are okay for fuel, but single flares are problems. Another possibility is your fuel pump. Have you done a pressure and flow check? Another possibility is your gas tank. Any possibility of any foreign matter in it? Could be something that floats around, plugs the outlet, and then moves away when the fuel stops flowing. It's sounding like the problem is either with the tank, pump, or somewhere between. If you're concerned about heat in the line from the pump to the carb, I doubt if the problem is there. There was a guy near here in the 70's who was wrapping his fuel line around his upper radiator hose to heat the fuel going into the carb. No problems with vapor lock, not even in 100+ temps. One more thing I just thought of, have you checked the shut-off valve at the tank? Mine had the needle and seat valve which had been buggered up, I replaced it with a 1/4 turn full flow brass valve. Just to double check, here are links to shots of my pickup, shows the fuel line routing.
Fred\'s Engine 1
Fred\'s Engine 2

I had the same problem in my 42.It was caused by crud in the petcock.I was amased at how restricted it acualy was.After cleaning it i got crud in the glas bowl plugging the screen and again starving the carb a couple more times but after that all was fine.

Thanks for all your help. Last night I replaced the sock in the tank, and the fuel line from the tank to the pump. After disconnecting the old line from the pump I noticed some gunk just below the fuel pump, the pump had been leaking, I removed the pump and the bottom was all messy, this pump is about a month old. So today I will be exchanging the pump and replacing it tonight. I made it home yesterday with stopping but just before I got their I opened the throttle and coasted into my driveway, the car started back up and I got under the hood, the gas in the fuel bowl would fill up then bubble and drop down, hopefully this is the fuel pump.