OK, So ive noticed there's a lot about Return line and kits on here, but no actual tech article. So I'm makin' one. Engine is a 89' 7.3l IDI. The kit I used was a Diapco kit that I got at my local Diesel shop. Cost was $75 CAD. PLEASE! take your time with this. It really didn't take me long to do it, and it was my first time, but that doesn't mean rush threw it. If you rush, there's a good chance you'll mess it up, and you'll be back at square one.

Once it's all back together, you don't need to bleed the system. I didn't with mine. It fired then stalled like it usually does (and this will probably happen as you've created an air pocket in the lines.) But I just cranked it over and it fired. Idled very nicely too, no more rough idle. No more smoke.

Tools needed:
5/8 wrench
pliers
razor
Vaseline
flathead screwdriver or small pry bar

Step One:
Remove the air intake.


Step 2: (not required, but helped me)
remove this bracket off the Water/fuel separator/filter head. Don't worry, it wont fall off.


Step 3:
Unscrew injector lines from injectors and slightly bend lines out of the way just enough to pull off the old caps. DO NOT over bend these lines. Make sure to leave the assembled when you take it off, not all 8, just one side. You'll understand better in step 5. If you seem to be having a hard time pulling off the old caps, you can use a flathead screwdriver or a prybar to get under the cap and pry up as you pull. Make sure to pull evenly all the way around.



Step 4:
Roll off the old O-rings off the injectors. I find that the best way is to push the o-ring to one side, and using your a finger, just pull up. Hold the side you pulled out of the groove, and keep going around with another finger. The next few pics'll explain a lil better



Then simply roll off the threads. It wont hurt the new O-rings if you slide them over the threads without anything on them. I've heard of people using electrical tape over the threads, but I find it doesn't make a difference.

Step 5
Now that you have the lines and caps off in one piece, lay it out. Get your new caps and match the "pattern". like so.

I find it helps when cutting the new line, take off the lines from the caps, and the clamps. Hold the old piece beside the new and align the ends. Then just cut the new where the old ends.

Once you've cut all your new line, lay it out like so


Now put it all together and put all the new clamps on.

Step 6
Now comes the time to put the new set of caps and lines back on. Here's where the Vaseline comes in. Take a small amount on your finger and wipe it around inside the cap. This will ease with sliding it over the O-rings. Also, before installing, I used a small nail to make sure the holes in the caps were free of mfc. tailings.

Repeat these steps for the opposite side of the engine.

Step 7
Re-tighten injector lines. Make sure to put them on finger tight first to prevent cross-threading. A lot of people just wrench them up and that's why they complain that their new kits leak twice as bad.


With both sides on, you can work on the rear line running by the Glowplug Module and the line on the fuel filter head.


With all the lines clamped, you can now re-tighten the injector lines to wrench tight. I think its exactly 22ft-lbs, but I may be wrong. And besides, I just tried to copy how much force I put into tighten them as I did loosening them.

Congrats! You've just installed your new Return Line Kit! I hope this thread has helped you. If there's anything you'd like to add, please feel free. Good luck Y'all.

 

Thanks for the write up. I couldn't initially find the o-Rings and ordered the whole kit from Memphis Diesel for $26. While waiting for the kit, I dropped by Tractor Supply and bought some hydraulic rated o-rings for $2 a pack of 8 x2 plus one for the one I always drop. Installed them left side then right side checking for leaks. It worked fine, All the old o-rings were inelsastic and brittle. The best way to remove them was pinch with small jaw needled nose pliers. Reinstall, using fingers and a small pick. My cups and lines were 3 years old so I didn't need to replace them BTW NAPA wanted $48 for the kit.

 

$26!! That's dirt cheap! I paid $75 Canadian for my kit, mind you it was a Diapco kit. They come with viton orings, and OE style lines.

 

Don't forget about the "olive" o-rings at the fuel filter head and back of the injection pump (two of the most often forgotten about, but usually most important parts of why people complain about air intrusion).
Also, as a personal preference, I install the caps first, and then cut my hose to fit. And I always cut a little long, so I know that I'm not going to cut anything too short. But that's just me.

 

Nice write up!

Jeff

 

What size are the olive o-rings? Do you have a picture. I have a Delphi kit and it only has the injector o-rings. Also the kit has copper washers. What are they for?

I will likely cut-to-fit because my lines are not straight. It certainly looks easier to cut the same as the old.

Great write up.

 

I might be able to get a picture if I can find the old spares I had at one time. The copper washers are for the bottom of the injector where it meets the head. Those are for replacing the injectors, not necessary for doing just the return line.

 

The real question is where did you get the olive orings?

 

I got them from Typ4 over on OB. He's also Type4 on PSN. Not sure if he's on here or not.

 

I completed mine last night thanks to you encouragement. My 94 N/A has the rear caps going to a "T" next to the glow plug regulator. I did not replace the line that went behind the engine. I need to find out where it goes see if the 8 inch piece of hose left is long enough.

It did not help my starting issues. I need to find the Olive O-rings and replace the rear line and see it that helps. The fabric on the old lines were soaked with fuel and I could smell fuel so it needed to be done.

I suspect the flow plugs are the next issue. I will test them tomorrow and replace the bad ones.

 

After much modification, I've decided that the stock path of the return line is annoying -- you've got that rear crossover line which is hard to get to, and if any of the fittings come loose, it's a pain.
I've revamped two trucks so far like this:
1. The rear corners end in plugs
2. The two front corners are Tee'd together, and then that line is teed together with the line from the fuel filter. That is then teed into the line from the IP return(basically, everything connects together right at the front of the engine where it is easy to get to). I then have a long piece of 1/4" hose which goes from there, over to the driver's side fender, and then down and back along the frame to join the plastic return line.
The steel pipe going along the top of the engine gets removed.

This mod doesn't affect function, though it makes it a ton easier to work on, especially when you add a turbo. It allows you good access to the return line right there at the front of the engine, if you want to add a small clear section to see bubbles, add a pressure gauge or anything else.
Removing the steel pipe also makes it easier to clean the top of the intake, or get your hand back to the back(really only an issue with a turbo).

I really should take a picture one of these days.

 

Yes a pic would be great. Would like to do that myself if/when I do returns. How did u plug the rear corners?

 

Brilliant! Please do take pics. This sounds like a great, simple solution.

A couple extra pieces of advice I'll add:

1. Removing the clamps on the injection lines can help get a bit more play out of them, eliminating the need to bend them (and risk damaging them). Only downside is that the clamps can be a bit of a PITA to re-assemble. You need a 3rd hand, basically. Do NOT run the engine without these clamps! The lines will crack if the engine is run for long periods of time without these in place (so I've been told).

2. Dental pick tools and a razor blade make getting the old o-rings off real easy. Both can be bought very cheap at places like Harbor Freight.

3. The Zicam bottle trick..... This is a trick that helps ensure installation of the o-rings without knicking the o-ring, which can lead to leaks immediately after finishing this job (very frustrating). Purchase a bottle of Zicam, then remove the clear plastic top from the bottle. Fit the clear plastic top on the end of the injector tip, then roll the o-ring (lubed with Vasoline) over the plastic top. BTW, if someone finds something cheaper than Zicam that would work for this, I'm all ears.

Mike

 

I used a pick to remove and install my O-rings. No leaks and it is good not to smell diesel fuel. I got a pair of picks out of the Advanced Auto $5 or $10 bin, the one with misc. tools. They are one of my most used tools. Perft for the O-rings, remove the washers on my front hubs, o-ring for the transmission filter, "C" clips, cleaning threads on bolts. Every one needs a pair in their tool box.

 

I fussed around with the pick until I realized the O-rings need not be saved. They were largely inelastic and I started giving them a pull with sharp pointed needle nose pliers and the job was over in 2 minutes per side. I used the pick to stretch the new O-rings into place pick on one side and rolling them down like stockings with my thumb on the other side,