M35a2 injector return line fittings

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acesneights1

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oddshot

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Great Job.

I see that the part number for these fittings is C74-158LF.

Do you happen to have a source and part number for the insert?

Also, where did you get the line? What size and part number.

Thanks
 

Ja1904

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The insert (compression sleeve) is attached to the 1/4 brass nut, make sure the old one comes out With the fuel line
You can get line from most auto parts stores just make sure it's fuel rated
 

rosco

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Ah yes...... something else I should do. At least it is on top, instead of on the bottom of the truck. Thanks for the reminder.
 

acesneights1

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The insert (compression sleeve) is attached to the 1/4 brass nut, make sure the old one comes out With the fuel line
You can get line from most auto parts stores just make sure it's fuel rated
It snaps off when torqued down so not reusable. I used Synflex. No issue.
 

acesneights1

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Great Job.

I see that the part number for these fittings is C74-158LF.

Do you happen to have a source and part number for the insert?

Also, where did you get the line? What size and part number.

Thanks
I posted the link where I got them. Just used plain old Synflex airbrake hose. Can get it at any Truck parts and most NAPA.
 
357
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Sorry to revive and old thread, but I am about to repair the leaky return lines on my M756A2. From the photo at the top of this thread it looks like the same compressions sleeve for a common 1/4" compression fitting available at any hardware store. Can someone confirm that please?

Also, the original clear hose was nice to monitor fuel line leeks, but I am not familiar with the hose itself. So, I ordered 1/4"OD Teflon tubing from someone on eBay, which should be clear enough to see bubbles if there are any, and robust enough to last decades. Does anyone know exactly how many feet of 1/4"OD tubing is needed to completely replace all of the return lines?
 

welldigger

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Sorry to revive and old thread, but I am about to repair the leaky return lines on my M756A2. From the photo at the top of this thread it looks like the same compressions sleeve for a common 1/4" compression fitting available at any hardware store. Can someone confirm that please?

Also, the original clear hose was nice to monitor fuel line leeks, but I am not familiar with the hose itself. So, I ordered 1/4"OD Teflon tubing from someone on eBay, which should be clear enough to see bubbles if there are any, and robust enough to last decades. Does anyone know exactly how many feet of 1/4"OD tubing is needed to completely replace all of the return lines?
The "correct" compression sleeves are not the same as plumbing compression sleeves.

However, I used plumbing compression sleeves on my truck when I replaced my return lines. They worked just fine. Not even a damp spot around the fittings.
 

m16ty

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You can get line from most auto parts stores just make sure it's fuel rated
Regular DOT air tubing works fine but it's not fuel rated per say. It's actually rated for air but will work fine without any problems.

I once used some plumbing tubing from Lowes for a return line because it was all that was available at the time and I needed to get home. The line got me home but soon turned very soft and wouldn't have lasted very long if I had left it on there.

I've also run into problems with trying to use ferrules from a hardware store. The problem is that tubing is measured from the inside dia. and DOT tubing is much thicker than what they sell for plumbing so that means that plumbing ferrules are too small to fit over DOT tubing.
 
357
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Prescott, AZ
Thanks, m16ty, and welldigger, for your contributions. I get that normal 1/4" compression ferrules will work, and therefore I will give it a try. I will get back with my results. I will of courser use tubing that can handle a wide range of solvents. Since I make my own fuel out of blending waste oils with solvents, then Teflon tubing should be able to handle any waste oil/solvent combination.
 
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acesneights1

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The ones I posted are the correct ones but regular ones work. I am just a stickler about using the right part if it is available.
 

deuce2

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That is very helpful. I just aquired an m35a1. Im still not sure of the year. I am trying to get it running after 10 years of sitting. It will definately need this done as well.
 

Menaces Nemesis

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I tried to use new Breakaway fittings from the OP link today, but 8 of the 14 nuts Supply House sent were out of spec. They measured .446 across the flats, way to big for 7/16 or 11mm, and too small for 12mm (would round over the corners instantly). The others that were in-spec (approx. .435 across the flats) would grab onto the tubing, but wouldn't let the compression ring break loose from the nut without twisting the tubing until it collapsed. And, yes, I had inserts slipped into the ends of the tubing. I wound up just cleaning up the old breakaway nuts I took off initially, and using new 1/4" compression sleeves from home Depot. No mods needed to the old breakaway nuts or new sleeves, and it all sealed up nice and tight.

Tubing; I couldn't find Synflex anywhere around where I live, so I wound up buying a Synflex air line from Summit Racing and just cutting the end valves off; https://www.summitracing.com/parts/air-20210 (I order a lot from Summit for my business, so I got free shipping. Otherwise, that "e"-auction site has about the cheapest Synflex price/foot I saw) It took right at 24" for the connections between the 6 injectors, and another 25.5" for the line from #1 injector back to the Injection Pump. I did a Manifold Flame Heater delete on my truck, so no tubing was used for that (so that might be something else you'd want to get extra tubing for if you still have the flame heater line and want to replace it.

Inserts; If I had to do it over again, I'd probably just get the inserts here; http://www.supplyhouse.com/Jones-Stephens-C74-100TLF-1-4-OD-Brass-Compression-Insert-Lead-Free-Bag-of-10 (Get 2 bags) 1/4" Inserts do vary in diameter a bit. Some will slip right into 1/4" Synflex, others might need a bit of force to get seated.

Compression Sleeves; (also called rings, collars, or ferules) I know the ones from Home Depot worked with my tubing OD w/inserts installed https://www.homedepot.com/p/Everbilt-1-4-in-Compression-Brass-Sleeves-25-Pack-800829/207176662 , but if I weren't in a pinch to get the job done, the ones from Supply House would have been less expensive; http://www.supplyhouse.com/Jones-Stephens-C74-005-60-4-1-4-OD-Brass-Compression-Sleeve-Bag-of-10 (Get 2 bags)

IMG_20171129_123230604_HDR.jpg
 
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Menaces Nemesis

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UPDATED 05/06/2018... SEE BELOW...
I tried to use new Breakaway fittings from the OP link today, but 8 of the 14 nuts Supply House sent were out of spec. They measured .446 across the flats, way to big for 7/16 or 11mm, and too small for 12mm (would round over the corners instantly). The others that were in-spec (approx. .435 across the flats) would grab onto the tubing, but wouldn't let the compression ring break loose from the nut without twisting the tubing until it collapsed. And, yes, I had inserts slipped into the ends of the tubing. I wound up just cleaning up the old breakaway nuts I took off initially, and using new 1/4" compression sleeves from home Depot. No mods needed to the old breakaway nuts or new sleeves, and it all sealed up nice and tight.

Tubing; I couldn't find Synflex anywhere around where I live, so I wound up buying a Synflex air line from Summit Racing and just cutting the end valves off; https://www.summitracing.com/parts/air-20210 (I order a lot from Summit for my business, so I got free shipping. Otherwise, that "e"-auction site has about the cheapest Synflex price/foot I saw) It took about 26" for the connections between the 6 injectors, and another 25.5" for the line from #1 injector back to the Injection Pump. I did a Manifold Flame Heater delete on my truck, so no tubing was used for that (so that might be something else you'd want to get extra tubing for if you still have the flame heater line and want to replace it.

Inserts; If I had to do it over again, I'd probably just get the inserts here; http://www.supplyhouse.com/Jones-Stephens-C74-100TLF-1-4-OD-Brass-Compression-Insert-Lead-Free-Bag-of-10 (Get 2 bags) 1/4" Inserts do vary in diameter a bit. Some will slip right into 1/4" Synflex, others might need a bit of force to get seated.

Compression Sleeves; (also called rings, collars, or ferules) I know the ones from Home Depot worked with my tubing OD w/inserts installed https://www.homedepot.com/p/Everbilt-1-4-in-Compression-Brass-Sleeves-25-Pack-800829/207176662 , but if I weren't in a pinch to get the job done, the ones from Supply House would have been less expensive; http://www.supplyhouse.com/Jones-Stephens-C74-005-60-4-1-4-OD-Brass-Compression-Sleeve-Bag-of-10 (Get 2 bags)

IMG_20180506_134714728_HDR.jpg
I've learned that curving the tubing between connections can be good for several reasons (See picture directly above);
- The curves allow you to remove/install the lines with far less likelihood of putting a kink in the tubing.
- The tubing will lengthen/shrink a bit with heat/cold respectively. The bends allow the tubing to expand/contract without stressing the tubing or fittings.
- Canting the injector "T" fittings and elbow fitting allows easier access to the injector hold-down bolts. So, let's say you want to check their torque, you can get at them with a socket/extension if needed.
- The distance between one set of injector t-fittings and another set may vary 1/16"+. So, if you pull the lines for service, and get their position mixed-up, the bends can absorb those differences in length.
 
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KevinGaus

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94F8F2E0-9196-4CDE-B01B-603B5BBFC798.jpgAfter I deleted the flame heater, I had enough transparent line to add in and look uniform. The transparent line is harder to get these days. I’m happy with it look of it.
 
357
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Location
Prescott, AZ
I bought 1/4" OD teflon tubing to replace all of my return lines with. While it is not as transparent as the original, it is transparent enough, and resists the widest range of solvents.
 
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