MEP-802/803 fuel return improvements

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Triton

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Is there a reason the return fuel lines have to be hose? What if they were hard piped in converting to AN or similar fittings? Seams like that would be just one less point of failure.
 

Ratch

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I know a few folks on here have been looking for fuel return hose and run into some difficulty.
Well after cutting all the return stubs and breaking one of the tee's, I was also in the market for some hose, but I also noted how crappy it is to have a slip-on rubber hose as a critical component like that. The military just needs it to work and be easy to fix fast, they're not looking at it as the last generator you'll buy for a while.
So after 4 months of searching on and off, I finally found some 5/32 diesel-safe fuel hose. In a hobby store...it's for model airplanes...

But that still sucks.
So I took some left over copper-nickel ("cupro" on amazon) brake line, and routed it along side the steel fuel line from the pump. I ran it into the fuel tank section of the housing, along the same path the rubber hose runs. I then routed it up about an inch from the brass nipple on the tank (the original return line connection), and made the final jump with the hobby store fuel line. I'll run to Autozone and get the proper fittings to connect it directly at some point, but this works for now.
The engine end of the line runs up the wall, to the dead crank switch area, underneath it, then bends outward to accept the hose from the injectors.

No pics, didn't want to touch my cam with diesel hands... More tomorrow.

Also, I've put an hour or test time on the hobby store hose, and it's excellent. No sign of break down. Only time will tell if it gets brittle.


Edit: sheesh, my 2 am write-ups leave a lot to be desired... More to come as I make this permanent.


Edit2: FYI, this is the tubing I used, though I only used about 5 feet of it. I had it on hand because I used it to replace the rust-prone brake lines in my truck.
http://www.amazon.com/AAS-Copper-Nickel-Brake-CN-316/dp/B00651OAVS/ref=pd_sim_auto_5?ie=UTF8&refRID=1T54CCA9HR6M1Y4V73A5
 
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Daybreak

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Howdy,
Good timing.
My MEP-803a is showing signs of the original braided fuel return line is weeping. I will be replacing all the fuel return lines and tees.
 

Chainbreaker

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Just an FYI - be aware that if anyone were to ever use BioDiesel Fuel, at some % mix, it is not recommended for use with Copper over time. Although the copper you are using has a nickel component so not sure if that makes a difference:

Source: http://www.biodiesel.org/what-is-biodiesel/biodiesel-faq's (under storage)

"In general, the standard storage and handling procedures used for petroleum diesel can be used for biodiesel. The fuel should be stored in a clean, dry, dark environment. Acceptable storage tank materials include aluminum, steel, fluorinated polyethylene, fluorinated polypropylene and teflon. Copper, brass, lead, tin, and zinc should be avoided"

Of course this recommendation pertains to 100% BioDiesel storage; not sure at what point the % of biodiesel, or how long it takes, when using X % biodiesel as a fuel it becomes a problem with the aforementioned metals. I have read various opinions that say typical biodiesel fuel will form a green slim over time when used with copper. Also, any water naturally absorbed in BioDiesel further exacerbates that potential reaction with those metals.

Since generators sit idle for a long time with fuel in them it would seem wise to avoid biodiesel, or those metals, if possible. Unfortunately here in Oregon we are mandated to use B5 minimum (last I heard). So since I can't avoid BioDiesel I don't add any of those metals to my fuel systems.
 

Ratch

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Finally got around to it... Here are pics:

Hard to tell, but the loop is intended to create a low spot away from the gen head in case of a leak.
WP_20150508_001.jpg

Tied to the housing
WP_20150508_003.jpg

Run alongside the fuel supply line.
WP_20150508_004.jpg

Temporary junction to fuel tank. Eventually, I'll put a fitting on this end, and adapt a short loop of hose in to provide some more solid leak resistance.
WP_20150508_005.jpg
 

Daybreak

2 Star Admiral
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Howdy,
Both MEP-802A and MEP-803A series fuel return line is 3.5mm ID and total usage is about 10 feet.

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

The manual just calls to make from bulk 503-1052.
The only thing which I would suggest is the best grade of fuel line which you want to purchase. I was thinking about the weed whacker line, but went with a high grade European diesel 3.5mm ID braided fuel line.
 

Ratch

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Where'd you find it? Got a link?
I'm not crazy about the hobby store stuff. I've thought about it a lot since then, and how little I want to re-do anything once the generator is in it's permanent home.
 

baja

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Hoping I do not break the rules on first post... so here we go.

I have found this stuff and use it for debugging my diesel pick up trucks. UV resistance and clear and strong and high tempt... chemical resistant.

Tygon
http://www.processsystems.saint-gobain.com/uploadedFiles/SGPPL-PS/Documents/Flexible_Tubing/FT-TygonTubing-Brochure.pdf


I am new to the diesel generators, just picked up three 531s and will have them in a few weeks. all 2007s and less than 100 hours

I believe Tygon is what the military uses for the clear lines i see in pictures on the generators for the clear tubing for the supply. These are UV protected clear. I bought some on ebay from a person claiming at least they bought it military surplus used for diesel so found the spec sheets. I have some and it is in my diesel pick up truck, it is not very flexible like rubber stuff so the clamp fit needs to be real accurate. It is rated good for diesel, bio diesel, and WVO too. You can see on the chart they have some real high temp ones. I do not see a reason it can not be used for return lines too. It can be found at McMaster Carr.


this has a great chart...
http://www.processsystems.saint-gobain.com/uploadedFiles/SGPPL-PS/Documents/Flexible_Tubing/FT-TygonTubing-Brochure.pdf

http://www.usplastic.com/catalog/item.aspx?itemid=23093

also from what I have read in various blogs the lawnmower stuff may be tygon.

tygon
Chemfluor® PFA Tubing
Excellent chemical resistance. Retains higher mechanical strength at elevated temperatures compared to PTFE. High resistance to stress cracking. Made from standard PFA resin (perfluoroalkoxy), Chemfluor® PFA Tubing is widely used in the semi-conductor, laboratory, environmental and pharmaceutical industries where ultrapure chemicals (including water) require precise quality control. Priced per foot; sold in full rolls only. Do not radiation sterilize. Working temp is -320° to 500°F.

I posted this info on 6.9 Ford truck forums and no one came back and said it was a no no. But no one also said they use it. But in general you get a no-no very quickly if someone sees a problem, there are quite a few profession mechanics on those forums.. I am same will happen here if it is a no-no.
 

m-35tom

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don't know where you got that info, but i think it is wrong. the original hose is DIN73379 type B 4.0 x 9.0 mm
very hard to find in US, i buy mine in England 50 ft at a time.
 

Daybreak

2 Star Admiral
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don't know where you got that info, but i think it is wrong. the original hose is DIN73379 type B 4.0 x 9.0 mm
very hard to find in US, i buy mine in England 50 ft at a time.
Howdy,
The manual.

NSN 4720-01-483-6467 part N20353.5 HOSE,NONMETALLIC
NameValue
CROSS-SECTIONAL SHAPE STYLEROUND
INSIDE DIAMETER3.5 MILLIMETERS NOMINAL
LAYER COMPOSITION AND LOCATIONOUTER LAYER BRAIDED COTTON CORD
INSIDE SURFACE CONDITIONSMOOTH
SPECIAL FEATURESCOMES IN A 20 METER ROLL (66 FT.)
MATERIALRUBBER BUTADIENE-ACRYLONITRILE CLASS NBR TUBE
MEDIA FOR WHICH DESIGNEDFUEL/OIL, HYDROCARBON SINGLE RESPONSE AND WATER SINGLE RESPONSE AND AIR SINGLE RESPONSE
 

m-35tom

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how do you push that on the barb fittings on a mep-802/3? as for the 4mm versus 3.5mm the 3.5 may be correct, but look at the end of a failed hose and it looks like it was no something to large. the 4mm is only .020" larger id but is still a tight fit so i think it may be a better choice anyway.
 

rustystud

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Location
Woodinville, Washington
how do you push that on the barb fittings on a mep-802/3? as for the 4mm versus 3.5mm the 3.5 may be correct, but look at the end of a failed hose and it looks like it was no something to large. the 4mm is only .020" larger id but is still a tight fit so i think it may be a better choice anyway.
You will have to replace all the fittings. A little costly up front, but then you have easy replacement if it ever needs it. Which (unless they get damaged somehow) will never happen.
 

Ratch

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I think you guys are thinking of two different hose systems.

One is the return from the injectors, that's the 3.5-4mm hose.
The other is tank to pump to ip.
 

rustystud

Well-known member
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Location
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I think you guys are thinking of two different hose systems.

One is the return from the injectors, that's the 3.5-4mm hose.
The other is tank to pump to ip.
Which hose are you talking about ? All the hoses can be replaced with the DOT nylon hose as long as you replace the fittings. The injector return lines are probably a different story, but if you can take out the fittings that go into the injectors and they are NPT threads then you can go with the nylon hose there also.
 

Daybreak

2 Star Admiral
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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
NameValue
CROSS-SECTIONAL SHAPE STYLEROUND
INSIDE DIAMETER3.5 MILLIMETERS NOMINAL
LAYER COMPOSITION AND LOCATIONOUTER LAYER BRAIDED COTTON CORD
INSIDE SURFACE CONDITIONSMOOTH
SPECIAL FEATURESCOMES IN A 20 METER ROLL (66 FT.)
MATERIALRUBBER BUTADIENE-ACRYLONITRILE CLASS NBR TUBE
MEDIA FOR WHICH DESIGNEDFUEL/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
 

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Hard Head

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I agree with the nylon. I have used tygon with nitromethane. Since bio crap came out and messed my fuel system up on my 939, I used the nylon hose to a re-circulation pump which is used to filter / heat to my fuel to keep it clean and warm in winter. I just used a 24v pump off a MEP. I can also transfer to and from my secondary 50 gallon tank now.
 
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