MEP-80x Fuel Return Line

[Daybreak]

Howdy,

The MEP-8xx series of generator all use diesel fuel return lines. After sometimes sitting with no fuel, or heat cold, no-use etc... they start to fail. The main issue is the lines start weeping fuel.

NSN 4720-01-483-6467 part N20353.5 HOSE, NONMETALLIC

Name	Value
CROSS-SECTIONAL SHAPE STYLE	ROUND
INSIDE DIAMETER	3.5 MILLIMETERS NOMINAL
LAYER COMPOSITION AND LOCATION	OUTER LAYER BRAIDED COTTON CORD
INSIDE SURFACE CONDITION	SMOOTH
SPECIAL FEATURES	COMES IN A 20 METER ROLL (66 FT.)
MATERIAL	RUBBER BUTADIENE-ACRYLONITRILE CLASS NBR TUBE
MEDIA FOR WHICH DESIGNED	FUEL/OIL, HYDROCARBON SINGLE RESPONSE AND WATER SINGLE RESPONSE AND AIR SINGLE RESPONSE

The fuel return line is 3.5mm ID. As you can see by the above posting the details of this line. Some have used other sizes and hose clamps. But purchasing the correct 3.5mm ID fuel hose makes it stay tight on all the hose barbs without issue.

I found the proper product at autoplicity. It is a 3.5mm fuel hose made by CRP CONTITECH. This is a roll which is 5 meters long which will give you enough to replace all your lines and have some in reserve. It is also known as yellow stripe fuel return line. Whether it is VW, Mercedes, Audi diesel type 3.5mm ID line. You can search for below

CRP N203535-5 CONTITECH Diesel Hose

 

[csheath]

For those willing to settle for an alternative that may be available at your local parts store you can use Gates Safety Stripe II 1/8"/3.2mm ID fuel hose. I purchased mine at O'Reilly Auto Parts for $1.39 per foot and it has performed without fail so far. O'Reilly's part number is 27000.



For the large crimped connection hoses on the pumps you can substitute Gates Safety Stripe II 1/4"/6.3mm ID fuel hose. O'Reilly's part number is 27002. I used this with their MasterPro fuel injector clamps. The bottom clamps are a little hard to tighten in the tight space but I feel better having clamps on those since they were originally crimped.




My experience with braided cloth covered fuel hose has been bad no matter what the size or application. It seems to fail frequently and without warning since you can't see the rubber being hidden by the cloth cover. I have 45 years experience working on vehicles that use this stuff from the factory and have seen it leak at less than two years old.

 

[Daybreak]

Howdy,

As long as its works.

 

[Daybreak]

Howdy,

The TEE's are
MEP-8xx Fuel return TEE 4730-01-357-8706
Onan part# 186-6177
Lister-Petter part# 751-13100

 

[csheath]

Any 1/8" barbed tee should work.

 

[Daybreak]

Howdy,

Yes, yellow stripe, VW hose, Mercedes hose, all those Europeon diesel engine hoses are the same.

 

[PoP PoP]

How is the connection made if I want to replace the rubber fuel line. I see going to the four injectors. But the connection to the end of the copper above the oil filter in the photo above is the question I have? Reference image above 1379.jpg

 

[Light in the Dark]

There is a barb in the end of that rigid tube. You would simply pull it off, and replace.

 

[PoP PoP]

Thanks. I had to replace one of the short ones today and was thinking of replacing all of it. I think I will stock pile the hose, tees and wait instead of (fixing it) Could make a problem where there is not one. Learned quite a bit today! Thank you for the help.

 

[Light in the Dark]

If you already have the cover off the top, just do them all. You WILL be thankful later when it doesnt fail when you really need it.

 

[Ray70]

Agreed! If you're in there now, just go ahead and replace it all. That hose eventually fails on pretty much every machine. I would also take the extra 15 minutes to remove the fuel tank cover and run the new return line all the way back to the tank.
Look at it like this... all the hose in your machine was made at the same time, all exposed to the same conditions for the same length of time. if it's starting to fail in 1 spot, the rest is not far behind.
Its better to do it now than have to shut down in the middle of an emergency to fix a leak.

 

[PoP PoP]

Okay I will replace them all while here. I needed the push to get me past the lack of experience on these lines. CSheath did a good job with the pictures. That helped bunches.