So i was redoing my glow plugs and broke off a return cap so i am in the process of replacing all of them. i noticed that there is 1 3 way return cap on both sides. Just like in the picture can i replace the 3 way with a 2 way or is that a no no? any help will

be great in the process of replacing them right now.

 

I'm pretty sure you have to keep the crossover line or else it's very difficult/impossible to bleed all the air out of the system.

If you didn't break either of the 3-way caps just reuse them, that's what I did.

 

You can just add in a brass tee between the caps if you don't have the right plastic fittings.

 

there is near zero pressure in the return system, and very low flow if you have eliminated the return from the filter head. the filter head return is a metered flow and check valve that returns air that collects in the top of filter head from slosh bubbles and foam pumped from tank buy the lift pump, the lift pump lifts many more times the fuel than the engine will consume. many people say that a TSB that says its ok to eliminate this return line to reduce air intrusion claim it works ok. however when eliminated all slosh or air bubbles must then pass thru the IP thus into the engine as there is no path back to the tank...this metered flow that passes around all the injectors also caries away heat back to the tank cooling the injectors.. IMO that many that blame air intrusion for hard starting don't have a good understanding of the fuel system and and GP systems that make the engine run. most any plastic or brass tee can be used reroute the return.

 

True, but you really shouldn't be getting air bubbles into the system.
And, there's a 'vent wire assembly' in the IP itself to do just this; it seems to work plenty well.
Which... doesn't matter one bit. The upper part of the injector is a solid chunk of steel.
The bottom of it is lubricated by fuel that is under pressure and is leaked out the return port. All under pressure so no fuel flowing 'by' the injector at the top will do anything.
And, most importantly... the injector is in contact with the head at both the threads on top and via a copper washer at the bottom. These areas will conduct heat quite well, both into and out of the injector. So, no matter what you do, the injector is going to be pretty close in temperature to the head surrounding it.
That's for sure...
Some people don't know how little 'air intrusion' matters when you make sure that the supply fuel line is full of fuel and not air. The entire return system then /does not matter/, except to keep fuel off of your pretty engine.
So you can route and tee whatever you want, just so long as it has a place to go, or you /will/ have diesel all over the top of the engine.

 

you can eliminate the one that goes from the passenger side front to the filter head, ford issued a technical service bulletin advising that back in 89 or 90 to help eliminate air intrusion.
the center ones provide a connection to each other, the driver side rear is the one that sends excess fuel back to the tank.
i use single tap caps on the passenger side ends, and driver side front.
if you do not have single tap caps, you can just use a short piece of hose and put a bolt in it with a hose clamp over it to seal it tight.
or if you have a non turbo engine, and only one three way cap, you can send the passenger side rear to the driver side that currently has a three way cap on it.
i would also replace all the lines with jacketed line, and replace all the o-rings with new viton orings.

 

Hi, You seem to be on the same type issue I'm dealing with. Recently purchased a 1985 6.9 and am having issues with startup due to air intrusion. First off, my fuel filter I removed to find only 1/3 full of fuel. I connected a clear fuel line from rear fuel filter Tee to first injector cap (return line). When I turn my engine over I get air bubbles along with fuel moving towards the first Jet. I had prior replaced all my caps O rings and lines with after market kit. The kit came with 3 45 deg caps. My old setup had tees with lines connected midway between the 2 rear jets. The new configuration allowed for eliminating the tee midway and running the line off the rear injector cap on each side. As is and was the setup on forward drivers side jet cap is. The prior setup had the line end at both rear caps. Technically linage is the same except it now passes directly through the two rear jet caps. Not sure if this would create my recent problem?


While cranking, not started Fuel moves from fuel filter with some bubbles towards first injector. Suddenly a gush of tiny bubbles enter line and slowly clear off and again a sudden gush of Bubbles entrapped in fuel. I stop cranking when fuel is in line and air bubbles continue to enter but slower and slower , almost coming to no bubbles entering. Turn key over and again gush of bubbles. When and if I do start I'll have grey blue white smoke which completely clears off after a 60 seconds. No black smoke and not really any smoke when driving/ shifting. The engine sounds great ... like a hyper sewing Machine. I can not seem to find any fuel leakage anywhere. Any Ideas as to where air can come from. The Caps are all pressed down and seem tight... can it be new after Market kit not sealing well? Shouldn't I see fuel seepage around cap if that the case? If injector caps had air entering would the air bubbles be moving towards the fuel filter from first jet or would the air intrusion more likely be prior to filter?.. I'm not sure how this system of fuel flows? I really would like to narrow the problem down as much as possible since I really hate wrenching outside in colder weather. Thanks!


Closer look at upper photo. My new setup is how his new caps came. Rather than setup with the Passover on the 3rd jet cap on each side they have you cross over on the 4th last jet cap. It worked out fine as for when running and likely not creating the issue I have?

 

If air's coming into the filter, check before the filter -- Cracks in fuel lines, a shot transfer pump, or a broken off "cone of failure" in the fuel tank can all cause this.

One easy way to isolate things is to get a length of 3/8 fuel line and a jerry can of diesel, Place the can under the truck and run the fuel line from inside the can to the input side of the transfer pump on the side of the block(it has two ports; one is a hose barb which connects to a piece of rubber hose. That's the one you want. Shove a bolt in the piece of rubber hose you disconnect to keep it from leaking). Start it, run it for a bit, let it sit(overnight?). If there's no more bubbles, the problem is before the transfer pump. If there still are bubbles, I'd look at replacing the transfer pump.

Depending, you may also be wanting to block off the return port on the filter once you get things figured out a bit more; it can let air into the filter and cause the filter to drain a bit.