Flexible fuel hose size(s) for 818

[MyothersanM1]

My 818 is continuously losing prime and it's driving me nuts. I had to limp back to storage yard today at 15-20 MPH. Luckily it was only a couple of miles.

I am in the process of bypassing the notorious "spider" (fuel tank selector) valve and going single tank. I pulled a couple of the smaller lines today and will try too get the rest tomorrow or next weekend. The old hoses have much to be desired. Does anyone know the correct size(s) of fuel hose for the flexible fuel supply and return lines for all dual tank 809 series trucks?

Can the old fittings be reused with regular hose clamps (worm drive type)?

Thanks in advance for any help.

BTW: Going to mount a tool box and will have a surplus fuel tank soon if anyone is interested.

 

[jwaller]

I used the old fittings and there is no need for hose clamps with those fittings. The line from the filter to the IP is 5/8. most of the other lines from the spider is 3/8 if I remember right.

just make sure you don't dent or scratch up the fittings when removing the old hoses.

 

[doghead]

Jwaller, the fuel line between the IP and filter has been 1/2" ID in the trucks I have replaced it on.

 

[wreckerman893]

If the 818 has the fuel tank selector switch (and I think it does) that may be the culprit.
They are bad about the seals shrinking and allowing air to be sucked into the system.
I bypassed the one in my wrecker and I think Tony Wright had to do the same with his.
Unless you are going to make long trips you can run off the drivers side tank and use a transfer pump to move fuel from the other side if you do have to make a long trip.
If you want the truck original there may be a source for the selector at Memphis Equipment or other ususal suspects. Or you might be able to rebuild it.
Just my input for what it is worth.

 

[Hammer]

1/2" ID from the tanks to the selector. 3/8" ID from the selector back to the tank.
You can easily replace the line from the filter to the IP with a -12AN hose setup.
With the cummins using the IP as the lift pump, you want the least restriction you can get.

If you plan on bigger power, run -12an from the tank to the filter and then to the IP. And use WM's plan on just using a transfer pump to move the fuel from one tank to the other.
FAR fewer places for air to enter the system, far fewer restrictions, and a pretty simple setup.

And all fittings be be reused. I put hose clamps over the the lines anyways, but they don't need them at all.

 

[jwaller]

Jwaller, the fuel line between the IP and filter has been 1/2" ID in the trucks I have replaced it on.

I just did mine fri and I replaced what came off it. 5/8. it's the same on another 818 and 816 I have to do.

 

[jwaller]

If the 818 has the fuel tank selector switch (and I think it does) that may be the culprit.
They are bad about the seals shrinking and allowing air to be sucked into the system.

fwiw I have rebuilt 3 selector valves and none of them had any seals in them at all and the tm doesn't show any. the valve and the valve block are machined brass and I didn't see any seals in any part of it. but I could be very wrong. but when I pulled it apart I cleaned it and reassembled it and none of the trucks loose prime and they all run strong.

 

[MyothersanM1]

Bump

I already have new fuel line from the filter to the IP. I just received some new 1/2" inch hose and 1/2" and 3/8" brass press-on fittings. I am replacing everything back to the tank including the return line. What the the best way to seal the threads...is Teflon tape or pipe dope good?? Not sure how they react with diesel fuel.

Thanks in advance.

 

[MyothersanM1]

If the 818 has the fuel tank selector switch (and I think it does) that may be the culprit.
They are bad about the seals shrinking and allowing air to be sucked into the system.
I bypassed the one in my wrecker and I think Tony Wright had to do the same with his.
Unless you are going to make long trips you can run off the drivers side tank and use a transfer pump to move fuel from the other side if you do have to make a long trip.
If you want the truck original there may be a source for the selector at Memphis Equipment or other ususal suspects. Or you might be able to rebuild it.
Just my input for what it is worth.

Thanks for the input WM. The selector valve is history and the fuel supply line is getting replaced straight from the left tank to the filter. I am taking the right tank out of service. My long range goal is to mount a tool/storage box in its place.