4/27/2006

 

Fuel System

You hop in your car and drive a few blocks and the sputters and dies. You were smart enough to use the original carb so you can pop the one bolt off and find no gas in the bowl and little fuel comes out when you turn the valve on inside the car.

The usual suspect is crud in the tank. What happens is you drive the car and shake up the stuff in the tank. You park it and the stuff settles to the lowest point, the fuel valve. You go to drive it and after a short while the engine gets fuel starved and dies. You pop the line off and blow back in to the tank and all is well for a while.

You could put a filter in the tank, but that does not help you get rid of the problem. You really want to take the cap off and the fire screen out of the tank and use a flashlight to see how bad is your crud problem. Shake the car a bit while looking in the tank. You need to be sure the tank is not very rusted and on the verge of problems. You then consider draining the tank and pulling the shut off valve out and putting in a ball valve and some pipe. Then put gas or kerosene in the tank, slosh it around real good and open the ball valve. Do this several times to get the worst out.

Then if you feel you got most of the stuff out then just put the valve back in as it was. If you want to be sure just put a short length of 1.4" copper tubing into the shut off valve so that the valve will not take from the very bottom of the tank. This requires that you have a good original filter screen on the filter bowl and the carb. You see the A was designed to eat dirt and Ford made the filters such that they will only pass crap that the carb could eat. Then he made the carb easy to take apart and dump the crap out of the bowl. By putting a tube up in the gas tank instead of a filter, you are allowing the junk through to be filtered out and removed. You will find the sediment filter on the firewall gets lots of stuff at first and after a few tanks and lots of driving you will find much less. Then you take out the little tube and now you tank is clean and you did not spend some extra money for a tank filter.

Here is is important to understand the design of the system. In 1930 they expected you to take in dirt so Ford made the system easy cleaning. The if you have a good operating firewall filter and the filter in the carb than you will catch everything you need to catch most of the time. Adding in a modern filter is not really all that necessary and may cause you more problems.

Vapor Lock

Here is a touchy subject.

A gravity system can not vapor lock!!!! The fuel will alway flow downhill and the vapor bubbles will always flow up hill, that is if the gas were to get hot enough to vaporize which I doubt could ever happen. Vapor lock is a condition where a fuel pump is unable pump through a vapor area in a line. This usually occurs when the fuel pump has problems. Back to gravity and vapor lock. Try this one. Siphon some gas in a clear tube with a loop in it and explain to me how the fuel always manages to get past the air bubbles in the high spots or if you straighten out the line notice how the air bubbles go up but the gas flow does not stop.

Keep in mind gasoline needs to be up around 300 degrees to boil most of the what makes up gas. That is pretty darn hot.

Vapor lock is what people like to think is wrong with their car when they can not find the real problem. The last vapor lock I fixed was a loose screw that locks the movable point. Most vapor lock problems are usually fixed when the electrical problem is fixed.