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Old 09-07-2015, 04:35 PM   #1
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Fuel line replacment

This morning I replaced the rubber fuel lines on the 310 in preparation for it to head to it's new home.

The main fuel line feeder is a 3/8" steel pipe that runs just forward of the rear axle up to the mechanical fuel pump on the engine. There is a 1/4' steel return pipe that runs right beside the feeder pipe.

Somewhere on the back side of the axle there are more rubber lines that head up to the top of the fuel tank. I didn't bother with those as I wasn't about to drop the tank to replace them. That's a problem for the new owner.

What I found as far as rubber lines kinda surprised me. I was expecting rubber lines at the electric fuel pump and at the mechanical pump. What I found was there are actually a couple of splices in each of the lines that needed new hose as well. I'm not sure why GM didn't run solid lines all the way but they didn't. It was pretty obvious where GM added the electric pusher pump because there is an unused section of 3/8" pipe that was bypassed for the pump installation.

I also changed the location of the inline fuel filter. As found the filter was located about 5' forward of the electric pusher pump. I opted to eliminate that filter and just used a section of hose in it's place. Instead I added a large filter on the suction side of the electric pump. Everything I've read about electric pumps is there should be a filter in front of the pump, not after.

Given that someone recently lost their Classic motorhome to a fire it might be a good idea to check or replace all of the fuel lines. A couple of the hoses that were on the 1/4" return line were obviously quite old and brittle. Until today I hadn't realized there were any splices in the fuel lines.

Brad
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Old 09-13-2015, 03:22 PM   #2
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Brad, it gets even more interesting once you try to figure out what SAE grade to use for non fuel injection supply lines. According to the little research I did, SAE30R6 and 7 and no longer being used by OEM's, they all switched to SAE30R9. Here is some good reading on the subject it also covers Diesel and biodiesel fuels

http://www.gates.com/oreilly/tech_ti...elLineHose.pdf
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Old 09-13-2015, 03:33 PM   #3
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This is a real problem as some auto supply houses aren't up to speed on the correct SAE info. Had to replace all the 3/8" rubber fuel hose that was sold to me recently as being the correct stuff for ethonol on a hot rod. Caught it before any problems cropped up.
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Old 09-15-2015, 09:21 AM   #4
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Any more it seems to be hit/miss as to what quality of fuel line you get from the parts stores.

I normally check when I buy the stuff but this time on the 310 I forgot too so I'm going to have to crawl under it to see what type hose I used.

That's what happens when you have to many irons in the fire

Brad
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Old 09-16-2015, 05:48 AM   #5
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Originally Posted by bkahler View Post
Any more it seems to be hit/miss as to what quality of fuel line you get from the parts stores.

I normally check when I buy the stuff but this time on the 310 I forgot too so I'm going to have to crawl under it to see what type hose I used.
That's what happens when you have to many irons in the fire
Brad
It's obviously up to us to make sure we get the right stuff. Any rubber line close to the engine compartment and any source of heat should be SAE30R9, fuel injection or not. Modern fuels and ozone apparently eat any grades below that in short order.
I am not taking any chances and started to replace all rubber fuel line with 30R9, including the generator lines. Later I will post a picture of what I found on this quest of paranoia
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Old 09-16-2015, 08:10 AM   #6
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Peter, do you plan on dropping the fuel tank to replace those lines as well?
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Old 09-17-2015, 05:11 PM   #7
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Peter, do you plan on dropping the fuel tank to replace those lines as well?
Brad, you know those dots you see all over a new cars mechanical items?
Sometimes even 2 next to each other. Quality control, double checking. This is what I believe everyone needs to do when they get their hands on an old coach like these...
I may leave the tank alone for now, since the lines are less than 10 years old Sae30R7 lines and just go from the rear fuel pump forward.
I already replaced everything in the engine compartment, which was converted to EFI. (without using EFI grade fuel lines)
Here is a section that was right above the right manifold that caused me to take a closer look.
Besides it being SAE30R6, I discovered three additional disasters in the making:
1. 1 missing hose clamp (well it was there but never tightened)
2. a misaligned leaking fuel filter
3. a deteriorating fuel filter element
fortunately this section was just before the high pressure
EFI fuel pump.
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Old 09-18-2015, 05:05 PM   #8
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Really makes you wonder what the PO was thinking when performing work like that.

I'll be dropping the fuel tank(s) on my Argosy and prior to re-installing I'm going to look at hard piping from the tank down to where rubber line installation would be accessible. I think it's a bad decision by the chassis manufacturer and Airstream to locate rubber fuel lines in a location where they are not accessible. I don't think dropping a fuel tank just to replace hoses is a reasonable expectation for an owner to have to deal with.

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Old 09-21-2015, 09:50 PM   #9
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It is so important to check those fuel hoses. I had replaced the two hoses at the fuel pump, feed and return, and at the carburetor maybe only two years ago. A year ago when leaving Burning Man, the return hose at the pump had a million cracks in it and was spitting out fuel under pressure! If it wasn't for my check list to look under the chassis for any leaks after starting the engine, I would have had my own burning art piece!

So we are heading to Yosemite in a couple of weeks. I've been doing a lot of maintenance and "checks". I crawled under to look at those two hoses. The return line is in good shape, but the feed line was cracked! That was a fire waiting to happen.

So that meant I needed to check the hose at the carburetor as well...a pain in the ass. Good thing I did, it had some signs of cracking as well.

The hoses were R6 and I replaced with R7...that's all I had with me at the ranch. They will certainly get me to Yosemite and back, but I will replace them all again in the near future with rocket engine approved hose...R9?



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Old 09-22-2015, 05:42 AM   #10
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..... but I will replace them all again in the near future with rocket engine approved hose...R9?
I was really ignorant to the facts outlined in the article I posted above.
I heard people complaining about todays fuel eating rubber fuel lines, without offering a solution. I have seen dripping fuel lines and once drove a Motorhome 200 miles home after only replacing the sections that were leaking...... What a fool I was.
The difference in permeation resistance AND by 50 degrees higher heat resistance makes it a no brainer despite the double or triple cost.
I am surprised that Ca, with its high emission standards has not made it mandatory.
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Old 08-04-2020, 06:02 PM   #11
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I am posting to verify some information and hopefully help anyone who sees this post in the future.

Is the common consensus really that SAE30R7 is not good enough for non-fuel injected motors?

I just replaced all my (non hard line) fuel lines with ACDelco (rebranded Gates) SAE30R7. Anything marked as SAE30R9 is listed as being specifically for fuel injected systems (with a much higher burst rate).

I wonder if things have changed since this post in 2015, or if the SAE30R7 I just installed really isn't going to hold up to modern fuel, even though the item description stated the fuel line was good for E85 (among the other fluids it listed).
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Old 08-04-2020, 06:42 PM   #12
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Quote:
Originally Posted by kidjedi View Post
I am posting to verify some information and hopefully help anyone who sees this post in the future.

Is the common consensus really that SAE30R7 is not good enough for non-fuel injected motors?

I just replaced all my (non hard line) fuel lines with ACDelco (rebranded Gates) SAE30R7. Anything marked as SAE30R9 is listed as being specifically for fuel injected systems (with a much higher burst rate).

I wonder if things have changed since this post in 2015, or if the SAE30R7 I just installed really isn't going to hold up to modern fuel, even though the item description stated the fuel line was good for E85 (among the other fluids it listed).

I tend to overkill, over think and over tighten bolts. That's why I seek advice from the smart guys and use a torque wrench.
I don't think you overkill using 30R9 on a low pressure system, but 30R7 should be sufficient. Cant be careful enough when it comes to fuel and heat.
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Old 08-04-2020, 09:20 PM   #13
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I tend to overkill, over think and over tighten bolts. That's why I seek advice from the smart guys and use a torque wrench.
I don't think you overkill using 30R9 on a low pressure system, but 30R7 should be sufficient. Cant be careful enough when it comes to fuel and heat.
Me too. If I can afford it, I overbuild everything. But sometimes (like during this damned epidemic), I've gotta pinch some pennies, and I think others might too. So I just wanted to verify for others that see this thread that 30R7 is actually designed to stand up to "modern" fuels, and 30R9 is more necessary when things need to be at more than 50 psi (fuel injection). I'd probably be installing pretty, braided PTFE if money weren't an issue.

FWIW, 30R7 is rated to 257 degrees F and 30R9 is rated to 275 degrees F.

The passage quoted below definitely has me second guessing my "money saving" choice though. Luckily, my rig doesn't have a lot of rubber fuel line, but next time I purchase any, I guess I will go with the more expensive 30R9 (w/ the added bonus that I can use that in my diesels).

Quote:
However, Gates Corp. engineers warn technicians that fuel formulations at many U.S. refineries are constantly changing as proprietary blends are introduced according to government mandates and seasonal influences. At times, more aggressive fuels can extract the oils that give SAE 30R7 hose its flexibility. The result is a brittle, stiff tube that will greatly reduce the performance and service life of the hose.

Fuel injection (SAE 30R9) hose or MPI (multi-port injection) hose is reinforced to handle higher pressures up to 180 psi. It can be used on all injection systems that use hose clamps. It is not designed to replace coupled assemblies on fuel injection systems.

Fuel injection hose is designed for low permeation contact with a wide variety of alcohols, alcohol fuel blends and diesel fuel. It allows 15g/m2/day permeation, whereas standard SAE 30R7 hose allows 550g/m2/day.

SAE 30R9 hose uses a laminated tube of Fluoroelastomer, as a thin wall inner layer backed by traditional compounds. This first layer protects the rest of the hose from attack, swelling or permeation from aromatics, oxidized gasoline (as can occur in fuel injection systems), ethanol or oxygenate additives and a wide range of petroleum-based products.
The laminated tube will resist cracking caused by “sour gas,” which forms when unused gas is returned to the fuel tank. As an added benefit, this hose construction reduces emissions because fuel can’t evaporate through the hose walls.

SAE 30R9 hose is also recommended for diesel fuel because its fluoroelastomer tube resists deterioration caused by some diesel fuel additives. As refineries produce cleaner fuels and lower allowable permeation rates during the “vehicle at rest” condition, older hose specifications such as SAE 30R7 are becoming less reliable. This type of hose is no longer specified on OEM automotive fuel applications because of stringent permeation standards.

Therefore, the best choice for automotive fuel line hose applications today is fuel injection SAE 30R9 hose for reduced comebacks, high performance and assured trouble-free service.

For submersible applications such as on the in-tank fuel pump, only SAE 30R10 hose should be used, because when the hose fails, the pump will fail. Hose construction consists of low swell fluoroelastomer compounds in the tube and cover that resist gasoline and diesel fuel permeation and aging. Standard hoses have these fuel-resistant characteristics in only the tube portion.

Courtesy of Gates Corp.
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