MEP-802/803 fuel return improvements

[Bluejoe]

The thing about DOT nylon hose is it can run any fuel. Gasoline, diesel, bio-diesel, kerosene, it doesn't matter. My one IHC (gas engine) truck has been running DOT hose for over 35 years now and no problems. We run this hose on all of our busses, have as long as I have been there which is 23 years now. When I worked at IHC trucks in the 1970's all the trucks ran DOT nylon hose. All the semi-trucks I have seen still run this hose. It is an industry standard.

Hello Rusty reading up on fuel line &returns. Like to see some pictures of your work if possible I know it’s been awhile since this post.

 

[majoday]

The Fuel Supply Line connected to the 4 injectors has a brass barb on the end. Mine is plugged. There is a number 50 stamped on the barb. I suppose it is a line restrictor of flow. Do any of yoy know the proper diameter of the restrictor, if indeed it is one?

 

[m-35tom]

Yes it is a restrictor so that the system is self priming

 

[Ray70]

This is just a guess, but when I first started working on the 802/803's I didn't realize that barb was a restrictor ( and this one was plugged ) so I stuck a drill bit in there and drilled it out, then realized I had drilled out brass and not garbage.
I used a small bit, probably 1/16" and it removed a little bit of material.... so I have a feeling that "50" marking may mean .050"
BTW, after drilling it out that gen still worked just fine.

 

[Light in the Dark]

Even if that piece of the hard line was opened slightly, it hits further restrictions down the pike with the Ts and final barb at the fuel tank.

 

[majoday]

Yes it is a restrictor so that the system is self priming

I thought that this was a good place for a restrictor.

 

[majoday]

I think I will begin with a very small bit and work my way up. Thank you all for the thoughtful insights. I was hesitant to proceed, but am now confident that I am on the right track.

 

[The Captain]

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. You can search for below

CRP N203535-5 CONTITECH Diesel Hose

Found the 15' roll on ebay for $42. Thanks for the part number.

 

[majoday]

I changed out mine for one used on the Mercedes Automobile. Fit perfectly.

 

[kayak1]

I left my panel light on the other night, after running the generator for a couple of hours yesterday I went out today to install a battery tender to find that everything is covered in diesel.

My return line is leaking rather badly and the fan is moving it all around.

After I picked up the generator I picked up 10' of 3.5mm line. I started taking the top off today and was able to unplug a section of the line, the shorter one from the side of the block to the 1st tee (the section that was leaking) #10 in the diagram.

Should I think of replacing the T's (#13), if so can you recommend a source?

Do I use a short section of the hose for #5 or is it safe to not touch #5 from the drawing?




I have taken the top off, and suspect that the back will need to get pulled off too to get the return line fully routed.

Thanks in advance.

 

[m-35tom]

no need to take anything else off it is very easy to get to. replace all the hose, the short sections are just as likely to leak.

 

[Light in the Dark]

All of the return lines, including #5, are all the same 3.5MM material (or the upgraded Gates). For the tees, I would chuck and put in new. I've bought them by the sack here: https://www.usplastic.com/catalog/item.aspx?itemid=104481

If you want a couple I will send them up your way. And yes, replace every inch of return line when you do the job... or you will just end up doing it again. Also use some small zip ties at all the barb fittings for a slightly more secure long term fitment.

 

[Farmitall]

I left my panel light on the other night, after running the generator for a couple of hours yesterday I went out today to install a battery tender to find that everything is covered in diesel.

My return line is leaking rather badly and the fan is moving it all around.

After I picked up the generator I picked up 10' of 3.5mm line. I started taking the top off today and was able to unplug a section of the line, the shorter one from the side of the block to the 1st tee (the section that was leaking) #10 in the diagram.

Should I think of replacing the T's (#13), if so can you recommend a source?

Do I use a short section of the hose for #5 or is it safe to not touch #5 from the drawing?

View attachment 883971


I have taken the top off, and suspect that the back will need to get pulled off too to get the return line fully routed.

Thanks in advance.

Start at the fuel tank!!!

I just did one of my generators. I started at the fuel tank and taped the new hose to the old and pulled the entire length of new hose through the bottom routing path.
Then made the fuel tank connection.

Then just worked my way up and around the engine, zip tied as I went and cutting where needed and zip tied everything.

 

[Light in the Dark]

I've tried it both ways, and I normally just put the spool of 1/8" line down where the oil fill battery would reside, and just pull to match the length of each section and cut in place. To each their own, whatever works.

 

[kayak1]

All of the return lines, including #5, are all the same 3.5MM material (or the upgraded Gates). For the tees, I would chuck and put in new. I've bought them by the sack here: https://www.usplastic.com/catalog/item.aspx?itemid=104481

If you want a couple I will send them up your way. And yes, replace every inch of return line when you do the job... or you will just end up doing it again. Also use some small zip ties at all the barb fittings for a slightly more secure long term fitment.

If you could send a couple up my way that would be great, I suspect they will arrive a lot quicker than the vendor.
Two of them from the vendor is $1.30 + Est. ground shipping: $17.73.

Glad to send you $ via paypal if you wouldn't mind shipping them. I won't put the top on until I swap them out.

I have replaced section #10 and the 2 #5's.

I can't see the fuel tank end of the long #15 section from the main compartment.

How does one connect the line to the fuel tank without pulling the back panel?

Thanks in advance!

 

[Guyfang]

By pulling the back panel.

 

[kayak1]

By pulling the back panel.

I guess I will be pulling the back panel. Thanks for the advice.

 

[Light in the Dark]

Yeah there is no getting around it, Just get a 5/16 nut runner for the panel bolts and a socket and crescent for the larger lower line of bolts. Easy on, easy off.

 

[kayak1]

Thanks for all of the help! The new line is in and no longer leaking.

I hooked the back on and will button the top up after I swap the T's out.

I knew that I was going to have to swap the lines out, but kept on kicking the can down the road past the time the work should have been done.

 

[kayak1]

All of the return lines, including #5, are all the same 3.5MM material (or the upgraded Gates). For the tees, I would chuck and put in new. I've bought them by the sack here: https://www.usplastic.com/catalog/item.aspx?itemid=104481

If you want a couple I will send them up your way. And yes, replace every inch of return line when you do the job... or you will just end up doing it again. Also use some small zip ties at all the barb fittings for a slightly more secure long term fitment.

Thanks for the barb fittings, they arrived today. I will swap them out Saturday.