QuestionI am stuck, I am having problem with getting fuel passed from pump into filter. Fuel does pump(brand new) filter brand new. Fuel Tank was flushed and clean up by radiator shop. Can a damper and accumulator prevent this flow. Those are the only two parts I have not replaced. Now that I am thinking about more in dept, may be the 5 inch line between the pump and filter is blocked some how. I know the pump is not backwards because the arrow points towards the filter. Any suggestions? Thank you Dick, you are the most experience in this bunch. This is regarding the 1978 Mercedes 450SLC.
AnswerAs you know, I don't really have any experience with these cars, but just to use common sense, let's start eliminating things from the list of possible causes.
First, use your home vacuum cleaner (if it has a blow out option) to put a little pressure inside the fuel tank, then disconnect the fuel line from the tank outlet and make sure there is fuel spurting out of there. It is quite possible that there is still some crud in the line that dips down into the tank to suction up the fuel. Don't exceed a small amount of pressure, because the tank can't take more than a few PSI. You'll have to wrap rags or something around the vacuum cleaner's hose nozzle to give a good enough seal so the tank can build up a little pressure.
If that goes OK, and gas does squirt out, then hook the fuel line back up and move to the front of the car, see if the gas will flow all the way up there to the inlet of the fuel pump or filter, (whichever comes first in the line). Keep up this until you discover where the blockage is. Then you'll need to clear that blockage, and if the problem isn't gone, keep going along the normal fuel path until you find the last problem.
Inside the tank, the fuel pickup line dips down to the bottom of the tank so it can suction gas all the way until the tank is empty. Often these pickup tubes get blocked by crud, and the cleanout process doesn't always get it all clean. If that is your problem, you can try shoving a small piece of piano wire down the tube to see if you can break through the crud. Sometimes "Gunk" brand or similar carburetor cleaning spray will help dissolve the goop. If you still can't get gas out of the tank, drain it and take it back to the cleaning place and tell them what is going on - they probably have better stuff to clean out the outlet tube.
One other trick I have used to cure this is to take off the gas filler cap (so that you can't build up pressure inside the tank), and then take an air compressor nozzle and blow back down the line into the tank. The lines can take a lot of pressure, so you can put some real oomph into it this way. If when you do this you hear "boiling" or bubbles forming inside the tank, you know the line is clear - then move to the next place in the fuel's path and investigate it. Be sure to take the cap off the tank, though, as putting full pressure back into the tank will cause a big bang and gas all over the place!
Good Luck
Dick
