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Spankrjs' 1984 Long Term Project

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
"Hot fuel" issues have been a near constant with this Scrambler since I started driving it. Basically, only down here in the deep South, during the hottest summer months, and only driving on the interstate at high speeds, after half a tank, the fuel starts vapor locking. This is the only time it does it, never around town, never off road, never in cooler weather. I am running an external fuel pump on this Scrambler, 3/8" Supply/5/16" Return (except at factory sending unit where it is 5/16"/1/4")

I have changed fuel lines since I started, I am now running the stock GM flex lines from the TBI unit to the passenger side frame rail, then stainless hard lines to the rear cross member, then a hodge podge of crap back to the tank. The last time I dropped this fuel tank was July of 2013, to un-kink the supply line. I had dropped the tank before this, to do an initial tank cleaning. But, I have never dropped it since I started having the "hot fuel" issues.

I was hoping to find a smoking gun, but didn't really find anything?

So, tank on the ground.

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This tank was perfectly clean when I installed it back in 2013. I had been mud riding a few times since, and the inside of the skid plate had lots of dried up mud. I took a few hours to clean the tank, skid plate, and anti rub rubber mats. If you go mud riding a lot, probably a good idea to drop the tank and clean out the skid plate every few years to prevent rust. There was also some Michigan sand in there!!

The Supply/Return lines at the sending unit were not kinked, but I still don't like this.

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When I originally installed this tank, I had the stock body mounts. So, I ran the lines like stock, across the tank to driver side, then to cross member, then back over to passenger side frame rail. Now that I have a 1" body lift, I can simply run the supply/return lines over the cross member,under the body, straight to the passenger side frame rail. This will remove (x3) 90 degree bends, and really clean up the plumbing. I will have to relocate the fuel pump, but that shouldn't be a problem.

This Scrambler is still running the OEM sending unit. I was curious to see if the pick up tube had a crack/hole in it, causing the system to suck air. No problem there, but the stock "sock filter" did finally fall apart.

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IIRC, the tank is 11-3/8" deep at the stock sender location. The pick up tube runs to the bottom, so the filter does not gain you any "depth" sucking ability. Inside this "sock filter", just hollow.

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From the factory, this filter comes crimped to the pick up tube. Most/all after market sock filters are a slip fit, which sucks.

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I did not have another "stock style" sock filter, but I had an aftermarket sock filter. It was a "slip fit", but seemed loose. The good thing, it is metal where it slips on the pick up tube. So, using my 60 watt soldering gun, I soldered it to the pick up tube. Not pretty with the big blobs of solder, but it shouldn't fall off.

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I was really hoping to find a cracked pick up tube, but it was fine. I checked where the pick up tube comes out of the top of the sending unit, looks like it slips through a fitting and is soldered in place. No leaks here, either.

The only "problem" I found was on the rubber fuel supply line. It was not leaking fuel out, but it did have this cut on it. I am not sure it even goes into the "wet" part of the line, but maybe it was allowing the pump to suck in air???

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Besides this one minor split, no other damage to the fuel lines. I was glad to see the 5 year old NAPA rubber lines showed no signs of deterioration. The split/crack was where I ran the line through the metal "loop" that is part of the stock gas tank strap. I won't be doing this again.

The tank cleaned, up new lines installed.

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I replaced the rubber fuel lines with new hose. Even though the old stuff still looked fine, cheap insurance. The picture above shows roughly how the supply/return lines will be run: straight out the sending unit, over the cross member, directly to the passenger side frame rail. This will make for a much more direct fuel line route, really clean up a bunch of hose/lines, and get the fuel supply lines 100% on the passenger side, away from the exhaust which is on the driver side.

I still need to relocate the pump, and finalize the plumbing. I am also going to check the vapor line for any blockages by blasting it out with compressed air. I did this before, and no problems, but will do it again, just to be sure.

That's it for now.
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
Didn't get to go to Hot Springs this past weekend, had to work/didn't feel well enough to go, but I did get this one running again.

I had the tank assembled and reinstalled, but went ahead an dropped it back down. Made two changes:

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I took the original plastic float off the sending unit and installed a brass float. The plastic float was still good, but.......

I also adapted/reduced/enlarged my fuel lines at the sending unit using these handy brass reducers I found at Jegs. The 350 uses a 3/8 supply and a 5/16 return. The sending unit has a 5/16 supply and a 1/4 return. So, one brass thing plugs into the 5/16 supply out of the sending unit and enlarges this line to 3/8, the other enlarges the 1/4 return line to 5/16. So, I have all the correct sized line, except the last 12" at the sending unit.

I broke down and bought one of those MasterCool flaring tools a while back. Love it. I used it to make the special GM fuel line flare and the "bubble hose clamp anit slip off" bumps on some new metal tube I ran.

The GM fuel line flare:

IMG_20181110_140903752.jpg

And an anti-slip bubble flare. Should be a hair smaller, but it works. If you don't stick the tube out as far as you are supposed to on the first step of a 45 degree flare, you get a nice bubble on the line. This bubble is hair bigger then I wanted, but it works. The brass Jegs reducers have about a 50 thousandths raised ridge, this is about 70 thousandths. But, the hose slips over, so good to go.

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One other flaring tip: After cutting the tubing square, I heated up the end of it with my little torch for about 20 seconds. This made flaring a breeze.

So, off the sending unit, rubber hose goes over the cross member to the fuel pump and the return line.

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Newly mounted fuel pump, new hard lines running behind the shock.

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I have the OEM metal tab/clips holding the lines, but I also put a big tie wrap near the shock, just for the hell of it. There is still clearance between the shock body and the metal lines.

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And my new metal lines running forward, where they tie into the OEM GM flex fuel lines that come off the back of the TBI unit.

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Need to go to the junk yard and pull off an OEM GM truck fuel filter holder, since I am running a stock GM TBI truck fuel filter.

Anyway, bunch of work, but really cleaned up the fuel system. I now have a straight shot, supply and return, running down the passenger side frame rail, from the tank to the TBI unit. Exhaust is on driver side frame rail.

It started right up, runs, doesn't leak, so happy with that.

That's it for now:wave:
 
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