SHIP4BRAINS
Full Access Member
Can that return to the filter just be blocked or must it be t-ed into the tank return?
please explain how
- Thread starter genchowford
- Start date
JwS
Full Access Member
There is supposed to be a check valve at the filter head to prevent any fuel/air from the return system from getting back into the filter head. These check valves are junk and typically don't work. I replaced mine with a proper check valve (with a very low opening pressure) and it works great. That way when I turn on the ignition and the electric pump starts up, it blows any accumulated air at the top of the filter head out into the return system and it never gets into the inj. pump. This is how i understand it is supposed to work.
It also helped when I moved the filter head from the top of the engine down to under the van, I left a T in the line up top with the check valve, and plumbed the filter vent through a restrictor back to the return system.
And now I can change the filter without taking apart half of my van and breaking my wrist. hehehe;p
It also helped when I moved the filter head from the top of the engine down to under the van, I left a T in the line up top with the check valve, and plumbed the filter vent through a restrictor back to the return system.
And now I can change the filter without taking apart half of my van and breaking my wrist. hehehe;p
My filter head is mounted on my frame under the drivers butt on the Moosestang. The return line goes to the tank, and the vent from the filter head goes to the return line as well. The return to the tank has a rubber nipple on it that acts as a check valve. Just to reiterate much of what has been said before about air and its effects.....
Sometimes in the course of drawing fuel from the tank, air is introduced into the fuel stream. This can be because of a fuel pump problem, airation of the fuel, sloshing of fuel in the tank... any number of reasons. Now, if your truck doesn't get rid of that air before it gets to the IP, a couple things can happen. Your timing may fluctuate, because fuel presure needs to be constant (the often reported "my truck took off like a pulling tractor with 5000 horsepower then died!).... Your engine may try to stop because there is no fuel at that moment.... or depending on the size of the bubble or bubbles, you may not notice anything at all. So, to make sure none of these things happen to you, Ford and IH put the fuel filter at the highest point in the fuel system. This makes sure that air COLLECTS there, and doesn't travel to the IP. Fuel presure will force this air down the hose to the return lines, not to the IP. The air in turn makes it back to the tank. It doesn't matter how much air is in the return lines when the truck is RUNNING, but it does matter when it is not. Here is why... when you shut down, all the air is going to go back to that high point. It is going to come up the return lines, come up to the filter head, and with no fuel presure present, fill the space at the top of the filter. This is where the hard start problem comes from. If you have a TON of air, or worse, a leak,(classic injector O-ring or cap problem) which lets in TONS of air... then your fuel level is going to drop in the filter. There is no check valve anywhere in the fuel supply to prevent the backwards flow of fuel, and even if there is, the weight of the fuel is going to probably push past it given time. So.... when you start after sitting a while, there is fuel in the IP supply line (albeit at zero presure - the transfer pump in the IP will suck it in just the same), and your truck is going to run for as long as that fuel is in the line. Usually about 2 or 3 seconds.
Now, how big is your air bubble? Is it the size of the fuel filter? It takes a while to fill that puppy. If you don't open the schrader valve, your mechanical or electric fuel pump has to push all that air through the tiny little hole that is in the fitting that connects to the return lines. Even then, once that is done, your IP supply line from the filter head to the pump is full of air. That air is going to go into your pump, and eventually out the IP return line in the top of the pump. That's a lot of cranking folks. Which is why so many of us dump the mechanical pump for an electric one. Air compresses, and fuel doesn't, so the pump is not going to try real hard to push air into your injectors, so for the most part, once you get fuel into the pump again, it's going to start. Now, this general malaise is going to lead to 2 other problems. The first is, your starter is going to get a work out, above and beyond what it normally does. People with chronic air problems have been known to eat starters. The starters often die because of other problems in the charging/battery/wiring system that lead to low cranking voltage and high current draws which heat the brushes and damage the windings. The second problem is, your glow plugs are being cycled and glowing, most likely with no cranking (electric fuel pump - while you bleed your air) or cranking (mechanical pump or trying to start). This is sucking down your battery, making that next start attempt that much harder on the starter, not to mention the glow plugs themselves. If you have an old style controller, it's potentially dumb enough to over glow them thanks to multiple cycles of the ignition key, and burn up your glow plugs. Bad glow plugs can in turn lead to bad starters...you get the idea. So you can see that air can be the root cause of multiple symptoms and problems that cascade.
So why did I mention where my fuel filter is? Because I wanted to see if anyone would notice that this makes my IP the highest point in the fuel system. Yup, If I get any air in my fuel, I'm going to know it right away. Not so good a design if your a consumer with no knowledge of how this stuff works. But, the interesting side effect is, that if my injector returns leak, the air will not be able to collect anywhere except in the return lines themselves. The filter is lower than the fuel tank, and my IP fuel return is at the filter head as well. This keeps air from being able to junction and get to my IP from the injectors. The very small bubbles that result from caviation in my fuel pump can exit the filter head and retrun to the fuel tank before they get to my IP. The truck runs great this way. The only downside is it runs like crap for a while after a filter change, and the entire IP drains out. To bleed it, I have to disconnect the fuel return from the IP, and let my electric pump run until I have fuel coming out. I've thought of putting a schrader on my pump outlet, but have not bothered yet. The Ford/IH design is a compromise for the best end user serviceability. It works just fine if you keep everything perfect, as I do on 2 of my other IDI's, plus my son's truck is setup normally. The Moosestang was built to experiement on, and now you know the results of that test. 40,000 miles it has been this way, and I may convert the others at some point. I happen to believe that not vibrating the heck out of a fuel filter is probably a good idea, and as long as your not worried about catching a rock with your fuel filter, the frame is a great place to put it. You don't have to worry about spilling fuel on you valve cover or filling your injector bore leaving you with that nice diesel smell for a few hundred miles.
Sometimes in the course of drawing fuel from the tank, air is introduced into the fuel stream. This can be because of a fuel pump problem, airation of the fuel, sloshing of fuel in the tank... any number of reasons. Now, if your truck doesn't get rid of that air before it gets to the IP, a couple things can happen. Your timing may fluctuate, because fuel presure needs to be constant (the often reported "my truck took off like a pulling tractor with 5000 horsepower then died!).... Your engine may try to stop because there is no fuel at that moment.... or depending on the size of the bubble or bubbles, you may not notice anything at all. So, to make sure none of these things happen to you, Ford and IH put the fuel filter at the highest point in the fuel system. This makes sure that air COLLECTS there, and doesn't travel to the IP. Fuel presure will force this air down the hose to the return lines, not to the IP. The air in turn makes it back to the tank. It doesn't matter how much air is in the return lines when the truck is RUNNING, but it does matter when it is not. Here is why... when you shut down, all the air is going to go back to that high point. It is going to come up the return lines, come up to the filter head, and with no fuel presure present, fill the space at the top of the filter. This is where the hard start problem comes from. If you have a TON of air, or worse, a leak,(classic injector O-ring or cap problem) which lets in TONS of air... then your fuel level is going to drop in the filter. There is no check valve anywhere in the fuel supply to prevent the backwards flow of fuel, and even if there is, the weight of the fuel is going to probably push past it given time. So.... when you start after sitting a while, there is fuel in the IP supply line (albeit at zero presure - the transfer pump in the IP will suck it in just the same), and your truck is going to run for as long as that fuel is in the line. Usually about 2 or 3 seconds.
Now, how big is your air bubble? Is it the size of the fuel filter? It takes a while to fill that puppy. If you don't open the schrader valve, your mechanical or electric fuel pump has to push all that air through the tiny little hole that is in the fitting that connects to the return lines. Even then, once that is done, your IP supply line from the filter head to the pump is full of air. That air is going to go into your pump, and eventually out the IP return line in the top of the pump. That's a lot of cranking folks. Which is why so many of us dump the mechanical pump for an electric one. Air compresses, and fuel doesn't, so the pump is not going to try real hard to push air into your injectors, so for the most part, once you get fuel into the pump again, it's going to start. Now, this general malaise is going to lead to 2 other problems. The first is, your starter is going to get a work out, above and beyond what it normally does. People with chronic air problems have been known to eat starters. The starters often die because of other problems in the charging/battery/wiring system that lead to low cranking voltage and high current draws which heat the brushes and damage the windings. The second problem is, your glow plugs are being cycled and glowing, most likely with no cranking (electric fuel pump - while you bleed your air) or cranking (mechanical pump or trying to start). This is sucking down your battery, making that next start attempt that much harder on the starter, not to mention the glow plugs themselves. If you have an old style controller, it's potentially dumb enough to over glow them thanks to multiple cycles of the ignition key, and burn up your glow plugs. Bad glow plugs can in turn lead to bad starters...you get the idea. So you can see that air can be the root cause of multiple symptoms and problems that cascade.So why did I mention where my fuel filter is? Because I wanted to see if anyone would notice that this makes my IP the highest point in the fuel system. Yup, If I get any air in my fuel, I'm going to know it right away. Not so good a design if your a consumer with no knowledge of how this stuff works. But, the interesting side effect is, that if my injector returns leak, the air will not be able to collect anywhere except in the return lines themselves. The filter is lower than the fuel tank, and my IP fuel return is at the filter head as well. This keeps air from being able to junction and get to my IP from the injectors. The very small bubbles that result from caviation in my fuel pump can exit the filter head and retrun to the fuel tank before they get to my IP. The truck runs great this way. The only downside is it runs like crap for a while after a filter change, and the entire IP drains out. To bleed it, I have to disconnect the fuel return from the IP, and let my electric pump run until I have fuel coming out. I've thought of putting a schrader on my pump outlet, but have not bothered yet. The Ford/IH design is a compromise for the best end user serviceability. It works just fine if you keep everything perfect, as I do on 2 of my other IDI's, plus my son's truck is setup normally. The Moosestang was built to experiement on, and now you know the results of that test. 40,000 miles it has been this way, and I may convert the others at some point. I happen to believe that not vibrating the heck out of a fuel filter is probably a good idea, and as long as your not worried about catching a rock with your fuel filter, the frame is a great place to put it. You don't have to worry about spilling fuel on you valve cover or filling your injector bore leaving you with that nice diesel smell for a few hundred miles.
SHIP4BRAINS
Full Access Member
You mention dumping the mechanical pump for an electric....what electric pump do you suggest? 
THECACKLER
Full Access Member
AGNEM....Nice rundown on the Air Thang. Good stuff !!!! I like it... Thanks
JwS
Full Access Member
I should add that when I relocated my filter under the truck, I also added ball valves on the inlet and outlet, so when I change the filter I can close them, keeping the fuel in the lines leading up to the inj. pump etc. Then I run the electric pump and let the filter fill with fuel before I open the valve on the outlet. Seems to work pretty sweet!
icanfixall
Official GMM hand model
You will find Holley Reds on Ebay from $25.00 up to $125.00. Just depends on who is listing them new or used. The Carrier pump seems to be a very good pump that will suck about 12 foot of head. They work well on semi truck trailers and thats where they usually can be found.
dont know if the return on the injector has to t-ed into the return to the tank but it was easy to do so I just went ahead and did it.
I blocked the line on the filter, no problems in 500 miles.
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