Just wanted to relate the experience I just had replacing the return lines on my 89 7.3 for future searching.

I noticed there is some debate on what size the the rubber return lines are on the injectors. Mine on my 89(and they were painted grey) are 3/16 inch line. I had to go to Napa to get 3/16 fuel line. I bought 5 ft, and used all of it. I would have had some left over, but I noticed on some of the turbo installs, the rear line is re-routed around the front of the air intake, so I went ahead and routed mine that way, even though I don't have a turbo(yet).

From doing a search, I found out that the o-rings are #111. I found these at tractor supply in the hydraulic fitting section. There were 8 in a pack for $2.99. I bought two packs, since I needed 16 o-rings. They are Buna-N rubber. From doing searches, some people were hinting that viton o-rings may be too stiff and not seal well, and silicone is not compatible with petroleum based oils.

One thing that threw me was the front injector on the passenger side. I didn't realize it had a extension on it for some sort of timing tool. I started twisting the nut on the steel line, and it started coming loose down on the injector, and not on the line. So I twisted the line a little bit, but it did break loose and then I discovered what was going on. If anyone else is doing this job, use 2 5/8 wrenches on this injector line. Slide the plastic sleeve up out of the way, and put a wrench on the first set of flats, and the put the other on the steel line nut, and then loosen the line.

I re-used the plastic caps, which worked fine. As someone said in another thread, and little grease on the o-rings after they are installed around the injector, helps the caps slide on with a little twisting motion.

 

You have posted some excellent information here, points to you. Knowing the O ring type instead of having to pay a "diesel premium" to get it from a diesel injection specialty shop will be a big advantage for others in the future. Some actually charge that price for ONE (1) single O ring to make you buy the complete set with caps and all because the price becomes close to that of a whole kit. I also have my rear return line routed around the front of the intake.

thanks for posting.

 

You did the same I usually do, sans the re-routing for the turbo, it works every time. Viton o-rings are for use mostly with veggie oil, for regular diesel and WMO the rubber will work fine.

 

super thread. i was looking for some of these o-rings the other week but no one seemed to be able to help. so yes i got suckered into buyig the whole kit.
thanks

 

I have found that a clear blue urethane fuel line works great for the return lines. It is more flexible than the rubber ones and doesn't seem to crack or get hard.

 

It would be nice if we could have a sticky for that info (among others). Little tid bits like that can make a big difference.

 

The preffered method now is write a tech article and submit it for the tech section.

 

Where you get that special fuel line?

 

The stuff I got is from Parts Unlimited:
Parts Unlimited | Street Catalog

I originally ordered it through a biodiesel supply company. I thought if they are selling it for biodiesel it should be fine for regular diesel. I can't remember what company it was, but is "made" by Parts Unlimited.

I'm not sure if you can get this directly from Parts Unlimited, but almost any motorcycle shop should be able to order from them (Parts Unlimited is a motorcycle parts distributor)

I googled "urethane fuel line" and found some other line, but don't know if it is the same as what I've got. You will need new spring clamps for it as it has a smaller o.d. than the old fuel return lines.

I've had it on my truck for about a year now and it's worked great so far. I occasionally run some biodiesel as an additive and it has held up fine. If I run into any problems like it suddenly has a catastrophic failure, dumps diesel all over my hot engine and burns my truck to the ground, you can be sure I will post the info on this forum.

In addition to urethane fuel line, I've seen Tygon fuel line, but I don't know if it is better or worse than urethane. I would think Viton would be good as well.
One thing I like about the clear blue urethane is that you can see any bubbles in the fuel line.

 

My 1993 takes the 1/4" return lines.

 

a quick search on the web came up with this online source:
PARTS UNLIMITED BLUE POLYURETHANE FUEL LINE from Parts Unlimited Street

I haven't bought from them, but it looks like the same line I have.

 

I also found a source online for #111 viton orings:
Viton O-Ring on Greene Rubber Co., Inc.

$16.98 for 50. If the viton seals work, that is a little less than buying seals at the dealership.

 

some cheap viton orings on amazon: Amazon.com: O-Ring -111 V90 (7/16 ID X 5/8 OD X 3/32 W) Viton 90A (Pack of 5): Industrial & Scientific

some nitrile orings on amazon: Amazon.com: O-Ring -111 V90 (7/16 ID X 5/8 OD X 3/32 W) Viton 90A (Pack of 5): Industrial & Scientific

I think nitrile is the same a buna-n and is diesel resistant. Check with your chemical engineer to make sure.

 

ok the last one:
oringsUSA