I am having some trouble with vapor lock on the fuel line. When the engine gets hot the fuel filter dries up but it continues to run. I checked the bowl and it isn't boiling. If I continue to run it, it will finally die. In about 20 minutes the fuel is back. This fuel nowadays sucks! The car I have it on predates evaporation measures, does anyone know of a way I can engineer a vapor removal solution for this? I have seen three-nipple fuel filters, but where would I run the third line? The carb is a '73 350 Century, bristling with vacuum ports that I have no idea where any of them go. Thanks in advance.
Try a test drive with no gas tank cap; to test if the vent for the gas tank is plugged. A plugged vent will cause a vacuum on the tank, making it difficult for fuel to escape. Jon.
I suspect something there Its funny you mention that. I replaced the gas cap a little while back because of the same problem with the same cap that the book reccomends for the car. But I noticed while the car was running the gas gauge was acting stange. It normally doesn't read right, low, but it went to about where it should have been for the gas thats in there. The filter stayed empty for a good four hours of my observation, I went to bed. I checked it this morning and the filter is full again, and the gas gauge is back down where it usually is. Is there a way to modify the cap to make it vent better? Its a vented cap for a non return application. I think I found the problem with the cap. You could draw on it and it would take in air, but, it has a surge valve in it. The thing is made ass backwards. If you blow on it at all like it would if you were venting vapor, the valve blocks off the venting. So I drilled a 3/32" hole in the valve plate and it now vents. I hope it works. My neighbor is a day sleeper, so I don't fire up the noisy beast until he is up Thanks!
There are two things to consider with this issue. One, correctly stated, is the condition of the fuel. It is presently set up for fuel injection, which pressureizes the fuel in the system, reducing the tendency to vapor lock. The other is the older vehicles' vapor control system, which needs changing as the fuel changes. The cap in question is used on vehicles with a vapor control system, ie. the vapor cannister, and lines. Rather than drilling the cap for the venting, you might try using a pre 1968 cap, which is less likely to use the vapor containment system. Your vent may cause the garage to fill with noxious vapors, and make the garage, and possibly the house stink of fuel. You might also consider the use of an electric fuel pump at the tank, which will pressurize the fuel to the mechanical pump, lessening its reaction to the engine temp. Since the mechanical pump pulls the fuel from the thank, it is more likely to vaporize, especially if any restriction exists. It may become necessary to bypass the mechanical pump, eliminating the source of heat applied to the fuel. You are correct regarding the changes to fuel in the last 35-40 years. Good luck, and let us know how things go. Ray
The cap The cap is a '65 model replacement and says "vented" , so it really should have vented it seems like. I wonder how widespread this is with replacement caps? If I notice fumes, I can fill the hole with epoxy and drill it smaller I think, or just get another cap. It might have just been defective. I think the electric pump will be next. I will wire it into the oil pressure solenoid to be sure it cuts off when the engine does. If I remember, it will need a timed relay to the run position, then it picks up power from the oil pressure solenoid. What size line should I run? I am thinking of 7/16" with a 5/16" return from the regulator. I have read in a few places that this will cool the fuel enough to take volitility out of the picture. I also at some point plan to put about 550 hp in the car, so it will need its oats. Your opinions?
Fuel return I had a similar problem in a Jeep one time. I found a Chrysler fuel filter that had 1 'in' and 2 'outs'. I ran the second 'out' back to the fuel tank (luckily, it had an unused port) so that either liquid or vapor fuel could return to the tank. This way, there is always a free flow of cool fuel throughout the system, or at least up to that filter. Worked very well!
