fuel flow drawing wanted, can't see how return gets in tank?

[Bart F-350]

'89 F-350.
after cleaning all fuel related parts before the engine, I want to install temporarily another fuel filter assy.

I can see the double fuel lines coming from the tanks, and I see where the fuel feed line to the HP pump is, and I see where the return hose is connected to the standard filter head.

I have the Idea that something is not right there? The return line connects to the filter unit by means of a restricted hose pillar in the head of the fuel filter.

and then I'm not aware of any fuel line connecting to the plastic return lines attached to the tanks?

can anyone here help me out?

 

[Rdnck84_03]

I would have to look at my truck to remember the exact layout but it should be on the top of engine near driver side injectors. Runs down the back of engine to the tanks.

James

 

[Bart F-350]

well, I just sit down after installing the new filter head, and I can confirm that's there, just a little brass hose pillar (at least that's how we call it).
and that has a restriction in it, a very tiny hole, which is needed to lose the eventually foam and air bubbles in the return circuit.
On that one you need to connect the plastic and hoses assy which connect the injectors.

But the thing I just don't get is where the original filter get it's connection to the return line back to the tanks?

all fluid connections my original filter-head has are: 1) big fuel-line in from the tank and pump. 2) smaller fuel exit to the injection pump. 3) the small brass hose pillar where the return fuel get's back to the filter.

For my idea I have to have somewhere another reasonable thick (plastic) line back to the tanks?

 

[Rdnck84_03]

It has been a long while since I have played with the return line setup on mine (redid it all in 2017 when I bought it and luckily haven't needed to touch it since) so unfortunately I don't remember exact layout.

I do remember that somehow the filter head, injector pump, and injector return caps all tie together on the return.

Hopefully someone will chime in shortly with all the info you need.

James

 

[chillman88]

There's a return line back near the drivers corner of the engine that runs down the back of the engine.

Factory return lines go from the filter head to the return caps and back to the rear passenger injector. Then over to either the driver's side rear injector or the T, I don't remember which.

Injection pump return goes to the return caps back to the rear injector then over to the T.

The "T" feeds back to the tank selector valve.

There were a few different variations over the years but that's the basic answer for you.

All of these references assume left hand drive. I know you're not in "the states" so I wanted to clarify just in case.

 

[Bart F-350]

yep, LHD here as well, I'll have a look later today if I can find that T you mean.
Thanks.

 

[Bart F-350]

one more question; if the whole fuel system is empty, what would be the best way to fill and purge it?

I prefer not to empty the batteries or cook the starter?

 

[franklin2]

Best way is to unscrew the fuel filter, pre-fill it with fuel, and then screw it back in. You will have a little cranking to do, but not as much as if the fuel filter was empty.

 

[Bart F-350]

are you sure? It's a whole distance, from the tank to the filter...

 

[chillman88]

If you're able, you can CAREFULLY put just a little bit of air pressure to the fuel tank while holding the Schrader valve open on the filter head

You don't want more than a couple psi though. I'd try it with someone else holding the valve open. You just don't want a lot of pressure.

 

[gandalf]

Going strictly from memory, and to reiterate some of what is said above, on my '92 CC dually, the fuel filter feeds the return line near the #1 injector, which in turn flows toward the rear, #1,3,5,7. The IP connects to the return system near injector #2, which again flows toward the rear, #2,4,6,8. The two sides do not connect at the front of the engine. There is a crossover line between #7 and #8, with a T toward the #8 side. To find that T simple feel along the return line after the #8 injector. It may not be easy to see. The return line, after the T, goes to the FSV, the fuel selector valve, where it again splits into two lines, one to each tank. The FSV controls the return flow according to which tank it is drawing from.

Understand, of course, that there are variations on this. Many trucks have had the return lines worked on, replaced, frequently changing the routing.

 

[franklin2]

are you sure? It's a whole distance, from the tank to the filter...

Are you stock with the stock filter at the engine? The filter will hold enough fuel to keep it running long enough for the fuel to get to the engine and the filter. I am sure you will have some hiccups and cranking, but you can't avoid it unless you want to run a electric pump. Even with a electric pump you will have some cranking if the injection pump and lines are dry.

 

[IDIBRONCO]

The filter will hold enough fuel to keep it running long enough for the fuel to get to the engine and the filter.

If it doesn't, for some reason, just remove the filter, refill it, and go again.

 

[Bart F-350]

Ok, folks, Thanks for the helpfull tips, If weather permits I'll occupy myself today.
I'll keep you updated.

 

[Bart F-350]

I found out about the hidden "T" in the return line, now I have a mental design of how this system works, thanks.
Is there a way to find out how big the both (front steel, rear plastic) tanks are on my truck?