Tygon for Return Fuel Lines(Success!)---W123
 

Had a fuel leak at the very back injector (nearest the firewall) on my '81 300D with '84 turbo engine, and after reading here and watching Youtube vids, figured the likely cause was a bad return fuel hose. The ones on it are the cloth-covered "Made In Germany" ones I've seen in other photos here on the forum and elsewhere, but I decided to see if I could get a quick fix locally by finding...some yellow Tygon that would fit. Here's what I've found:

1. The size that I bought was .117 inches ID, .211 inches OD. I only bought a foot of it to see if it would work.

2. Yanked off the offending leaking return hose; that was fairly easy. However, after measuring and cutting the Tygon to the same size as the original, I found that pushing the Tygon on was well, tight. I wasn't getting along very well by doing it by hand, so I tried rubber gloves (that didn't help; believe the seeping leftover fuel was the culprit), then a paper towel between my fingers and the Tygon. That did the trick, as I was able to bottom out the Tygon on both barbs.

3. Started the car and everything ran normally. Only weird thing I noticed was that the Tygon, due to it being more flexible, "shakes" with the car---you can clearly see it vibrating (the cloth ones do not). Don't think that will be any concern until the Tygon gets some age on it (2-3 years?) and causes it to crack around the barbs. So what, I say; from what I've read, these hoses should be replaced in that time frame anyway. After a day, I noticed the barbs and injector were bone dry, so my fix worked. Since the others aren't leaking, I'll leave them for now, but have bought another 3ft to do those when necessary.

Online, I discovered that .117 inches is just a shade smaller than the 1/8 inch I've seen mentioned elsewhere. It appears this .117 inch stuff is smaller than 1/8 inch, but larger than the 1.9 mm ID of the original.

I would put a link on here where I got it, but since this is Pelican's forum, I'm guessing they'd rather not have me posting links from competing auto parts stores. If anyone knows if it's ok to, I will post it in the future. Or you can PM me if that is allowed.

It has previously been posted that Lawn Mower, Chain Saw and small engine shops sell the Tygon Fuel line.

I have also seen like 6 inch sections of it selling in some auto parts stores if they have a section that has lawn mower spark plugs and air filters and such.

I've had Tygon return lines for about 6 years now. Still working fine. Mine wasn't quite as tight to install as yours sounds, so you might have splitting issues sometime down the road, but I wouldn't stress over it, it's just the return lines.

Here's a couple of pictures with it installed. You'll note on the first one there appears to be a little bit of fuel still coming by that last injector. I discovered that, lo and behold, the back hose plug was...quite leaky now, too! Yanked real hard on that hose and...the top came off but the rest stayed on the barb! Great...only thing I even remotely had with me that might work to get that off at that moment was...a pair of scissors. So, I go to work cutting the old hose off the "nail" (plug) in the original hose (took awhile) and then used the scissors to basically destroy and pull off the original hose from the barb on the engine. That original was quite stiff and crumbly. :) I will attempt later to post a video I made to Youtube where you can see the Tygon vs. original, so you can see the "shaking" I mention in regards to the Tygon.

You can see from the second shot that I stuffed the plug in one end and installed. A later check showed that the area is now dry. Since I've seen other posts with references to other parts suppliers; here's the link to the stuff I used. Whether a local store near you will have it, I can't tell ya.

Prime Line Tygon 7-08160-5 - Vinyl Fuel Tubing | O'Reilly Auto Parts

Here is the aformentioned vid. I used Vimeo to post this and found by attempting to play it, I couldn't in Firefox, and Internet Explorer wanted to constantly Autoplay another video after mine and Autoplay couldn't be switched off. So...I'm sure most of you use Google Chrome at least sometimes; go to the link in Chrome and it plays fine, with Autoplay on/off and ad blocker installed. It will play here below in Chrome, but if you want to see it full screen, click on the "Vimeo" logo in the lower right hand corner.

https://vimeo.com/179284973

You'll see the Tygon hose shake and shimmy, but not the original return hose to the left of it. Again, don't think it matters that much, with the Tygon's flexibility.

Same deal with my cloth-covered "Made in Germany" hose, after ~3 yrs they were leaking profusely. Seemed to have started all at once, and every section was wet, so at least the hose is consistent. I have been running Diesel HPR for several years, on and off when I had the car vs my son. I first tried silicone vacuum hose on one section since I had it, then read "doesn't work" and indeed it started swelling in a day. I now have Viton tubing for >2 weeks, and looks fine, but a few years to really tell. I bought from China $19 for 10 ft on ebay, claimed good for bio-diesel. Any way to tell if genuine Viton? Maybe a bite test, like a gold coin? It is a flat grey color, if that tells anything. Maybe cut off a piece and immerse in solvent for a day? I have ethanol, MEK, acetone, and xylol.

"The working temperature range ifor Viton® is considered to be -15 to +400 degrees F (-29 to +204 degrees C), but it will take temperatures up to 600 degrees F"

Maybe try a soldering iron which is around 800 to 900 F and see if it melts?

What is the wall thickness of your Viton tubing? I had some Viton return lines on a WVO car a while ago and the wall thickness was very thin...less than 1/16" and it pops off the nipple with very little pressure.

I have these http://www.mcmaster.com/#5792k32/=13s9wwj Polyurethane clear tubing for return lines on my 85 for about 3 years now with no leaks. They don't stay clear very long and turns to a light to dark brown after a year or so.

I also had the same lines on a WVO car and the WVO makes the polyurethane harden over time. I had one leak and snap off at the barb.

After reading this thread I picked up 10' of 1/8" ID tygon to try on my OM606. Its kind of interesting to see the fuel bounce around inside the return lines at idle. While I was in there I also ditched the leaky plastic crankcase ventilation with brass fittings and rubber hose going to the airbox.
http://i.imgur.com/tvxxIYx.jpg?1

Any fuel leaks tent too pool in the injector wells on the OM606 but the cross over pipe makes it difficult to inspect so I cut the plastic injector cover into 2 pieces for quick access.
http://i.imgur.com/8a8ZY7h.jpg?1

Photos at #1 injector and at fuel filter. You might be able to scale to determine the wall thickness. I would guess more than half the ID. Been about a month and no sign of degradation and it has been hot here w/ engine usually running ~100C on the dash gage (another issue). The hose certainly doesn't want to come off. But, the "Made in Germany" woven hose I had before looked fine for several years, then started getting wet everywhere, and dripping fuel on the cylinder head.

If you see an ebay ad "$19 for 10 ft w/ free shipping from China", that is probably the one I bought. They claim for M-B diesel. I kind of fell into owning two 300D's, but does make it worth buying parts in bulk. I bought the 1984 for its engine to replace my 1985's failed engine, then fixed both cars, so kind of committed to these guys now.

I picked some of this up because my braided hose is starting to weep fuel and get crunchy.

https://www.amazon.com/gp/product/B00V9XRZYQ/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

Looks like it will work just fine based upon you all's experience.

Out of curiosity, what exactly is one supposed to see in the lines? I pictured a steady stream of fuel, but there doesn't seem to be much of anything, really. Under what condition does a lot of fuel get returned from the injectors?

Anyway, clear lines are interesting to look at, that's for sure.

-Rog

With my car, I see a little bit of what I would call an air bubble at the top of the hose, and fuel. That's pretty much it.

Don't think the "air bubble" is much of a concern. Car has run fine otherwise.

Sounds like what I'm seeing. I guess most of the extra fuel control takes place at the IP then. It would be interesting to see what difference a hot rodded pump makes.

-Rog

FYI, the original hose is 3.2mm ID, the wall thickness is 1.9mm or 7mm OD. So 1/8" ID is as near as makes no difference for those looking for something easy to find.

-Rog