Air at filter schader valve

[J.P.]

Hey I'm back, been awhile, sold the motorhome now have a 87 F250, was running fine and has been sitting a while, narrowed down the hard starting and rough Idle and dieing. if I get it started and run around front and hold in the schader valve I get air out of the system and it idles fine, if I let go in a minute or two it goes back to rough Idle and may die, it dies it on both tanks and I have checked for leaks. I am thinking i will bypass the water sep. tomorrow and see what happen. could the lift pump cause air in the system? Thanks glad to be back

 

[gandalf]

An '87? That has the water separator on the driver's side fender, back toward the hood spring? That design was NOT one of Ford's better ideas. It has a little pull ring which opens a valve to allow accumulated water to drain out a tube on the bottom. The problem is that the valve frequently doesn't close properly, and allows air to enter the system on a steady basis.

As I see it, you have two choices to verify whether this is the problem. You can take that separator out of the system bu plumbing around it. A perhaps simpler, though temporary, method might be to plug the drain tube. If you can plug the tube you will eliminate the air leak. If you can verify the leak, fixing it is a lot easier.

 

[IDIoit]

i by-passed my WS all together. could not get it to seal for nothing. and you cant buy a new OEM one.

 

[J.P.]

Ok This may not be my problem, I have a pair of visegrips on the drain hose already... here is some more history. when I got the truck the front tank was not working and the rear tank was returning to the front tank, so I started with the transfer valve and found the switch was bad, replaced it and now you can hear the valve switching and was working fine, I tested the valve by removing the return lines, put a hose onto each one into a bucket and while switching the return lines worked correctly. Prior to this and since this truck had been sitting awhile, I fixed a couple of return line leaks and replaced the filter, I have also tighted hose clamps etc. The system seems to be tight, could the lift pump or the ftv be letting air in the system? or what does the small hose do that comes back to the filter outlet do? it seems that the air could only be getting into the system from the supply side not the return side??? I was going to bypass the ftv next with just the rear tank and see what happens. Both tanks are full I had only put about 50 miles on it, and yes the gauge is pegged to the right on both tanks ( work on that later...) Thanks for the help

 

[J.P.]

Ok I had a chance to work on the truck this afternoon, I decided to put a positive bypass on the water sep. and guess what, fired the truck it ran and idled fine so rather than leave the double barb fitting in I installed a looped hose and will deal with it later, my guess is that it can leak from other than the bottom drain. I am going to drive it to work tomorrow and we will see what happens. Thanks for the help