fuel line changeout

[Megunticook]

Well, I think I've got everything I need now to tackle that fuel line replacement. Looks pretty straightforward, but I wanted to check in with any folks who have done this on their own truck in case they have any tips/suggestions.

Basically I'm replacing everything from the tank to the carb except for the pump (should I do that too as preventive maintenance?). My tank is in the cab, so it's not a very long run.

First of all, I presume you want to drain the fuel out of the line to minimize spillage. So first detach the hose from the tank, then the other end at the pump (with catch basin ready)?

I ended up deciding to get some metal line (the same copper-nickel alloy I used on my brake lines), stuff bends fairly easy (not as easy as copper but not as hard as steel), so I'm hoping the installation goes pretty smooth. I will have to cut it and flare it myself. I guess any old flare will do the trick with the hose and clamps, right? All I have is a double flare tool. Seems like the factory stuff has a different flare on it, but I don't suppose it matters. Correct me if I'm wrong (obviously the flare will matter on the line from the pump to the carb., which has to properly seal with a nut fitting).

The existing line from pump. to carb. is one I installed about eight years back, crudely bend by hand (works but not quite as neat as factory). Can anybody with a 318 send me a photo of how the factory fuel line snakes up to the carb?

Final question--when everything's installed and it's time to fire her up, there will be nothing but air in the line between the tank and pump. Won't this cause the fuel pump to cavitate and lose its prime? Do I need to fill the new line with fuel first by siphoning from the end by the pump?

Any further tips and suggestions welcome.

And yes, I will make sure I disconnect the ground cable from the batter before I start (ask me how I know that!) and there will be a fire extinguisher handy just in case.

[Speed Dragon]

Sounds like you got it all figured out. I don't think the fuel pump will cavitate, it's a diaphragm style which I don't believe is capable of cavitating. You could prime the line, but it's unnecessary IMO. Pouring a bit of gas down the carb and firing it up once or twice should do the trick. I think I have a factory line on mine from the pump to the carb, if so I'll get a pic for you.

[Megunticook]

Thanks, a picture would be great.

[Megunticook]

I don't think the fuel pump will cavitate, it's a diaphragm style which I don't believe is capable of cavitating.

Right you are. I installed the new line yesterday (just did tank to pump), didn't bother to prime, and it ran fine.

If you (or anybody else out there with a 318) get a minute, snap a shot of that line to the carb., I'd like to see if I can replicate it. What I put on there 8 years ago is pretty rough (hey, it was my first try at bending a line--surprised I didn't kink it all to hell).

By the way, I found that you have to use a real light touch in making the flares or else you'll never get the hose on the tubing--the tool I had only did double flares.

This cunifer (copper-nickel alloy) stuff is awesome, by the way--at least if you're plagued by rust like I am. Apparently Volvo started using this stuff back in '79 for their brake lines, now a bunch of European manufacturers do it. Costlier material than steel, no doubt, but no corrosion issues.

The factory line I removed was flaking pretty bad, but not as weakened as some of the brake lines I removed last year (a few were so badly corroded all you had to do was bend them a little and they broke in two).

Interestingly, the metal portion of the vent line that goes from the tank to that cannister by the radiator (just a portion is metal, from about the passenger side rocker panel to the inner fender) is literally disintegrated--a 2-3 foot section is just gone. Don't suppose it matters much (this is supposed to just limit gasoline vapors escaping to the atmosphere, right?) but I suppose I might slap a coated steel line in there at some point.

Is it just me, or are some of the emissions control systems on these era trucks pretty half-assed? I understand why the EPA wanted Detroit to start looking at ways to reduce emissions, but some of the stuff the Detroit engineers came up seems hare-brained.

[Speed Dragon]

Here's a couple pics, little blurry but good enough to see the line. The curl at the carb isn't really necessary unless you have A/C, I think.

[Megunticook]

Thanks--helps me get a better sense how to properly route it.

What exactly is going on by the pump? Is the metal line to the carb wrapped in hose? That to keep it insulated from heat?

And on mine, I have the filter attached directly to the pump with a short piece of hose (the kind that comes with the NAPA metal filters, about 3 inches long or so). What's going on with yours? You just have a longer piece of hose there?

I'm just curious--my filter's kind of a PITA to change because the hose between the filter inlet and the fuel line on the frame has to bend about 45 degrees or so--not the best arrangement.

[bherder]

Meg, what you basically wanna do is, keep the fuel line as far away from heat as possible, OR make sure it gets plenty of air-flow over it.

You'll note that your fuel line probably runs from the tank, underneath the frame, and then runs to the pump with a sharp bend to it. Keeps it away from exhaust heat. Then from the pump up to the carb which keeps it in the full air-blast from the fan. Again, keeps the fuel cool.

I learned my lesson LONG ago when I had my A-100 van. Working on the engine one day (Right before vacation, no doubt) I wondered 'WHY does the fuel line run ALL the way up to damn-near in front of the radiator, then BACK to the carb?"

Well, being the freekin' GENUSIS that I am, I decided that Dodge didn't know what the hell they were doing, and re-routed the line in a more 'direct connection' ... The result was, unless it was 50 degrees or less outside... Vapor lock, big time.

It took me about 1000 miles and 6' of fuel line somewhere in the middle of NOwhere Oregon to finally figure that one out... :D

Hahahaha ... One of life's little embarrassments ;) Keep in mind, I didn't have to tell y'all that! :D

[Megunticook]

Thanks for sharing the story. That must've sucked. I've done similar bonehead things, enough to hesitate now before second-guessing the engineers who designed the vehicle.

I noticed when I pulled the old fuel line that someone (factory?) had put a rubber hose sleeve over the last 8 inches or so of line--I guess as added insulation? Doesn't seem too close to the manifold there, but I suppose that might be the warmest spot.

I didn't replace the sleeve, but probably should take a minute to do that.

[Speed Dragon]

Yeah sorry, should explained the pics a bit hehe. The hose by the pump is where a filter used to be, that engine is originally out of my Dad's old '85 van we junked out, and that's where the filter was on it. Most older trucks have the filter before the pump, just like I have it.

And yeah I have a longer hose where the filter is, makes it a bit easier to change I think. Also if the filter happens to clog on me sometime, the hose from the filter to the pump is long enough to reach the frame line also, so I can bypass the filter if need be.

If you run the line in the factory location inside the frame rail up to the pump, you should have no problems w/ vapor lock.