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Fixing Fuel Tank Leak

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Shortly after purchasing my truck last November, I filled it up to get an understanding of how accurate the fuel gauge was. I found out it was somewhat conservative (~ 8 gal left when the light comes on @ the 1/8th tank level), and also found that the tank leaked fuel when full. Last Friday it had finally gotten warm enough & the tornadoes have subsided enough for me to drop the tank to find & fix the problem. The source of the problem was at the top of the fuel tank module. The lid of the module holds four components; the level sender electrical connector, the fuel suction/return lines, the roll-over valve, and an unused capped-off extra fuel line. Each one of these components is plug-shaped, about 1" in diameter, & is seald onto the lid with a rubber grommet. My problem was that the fuel suction/return line component had rusted through; not the lines themselves but rather the sheet metal that formed the plug & supported the lines.I called Mike to ask his advice on where to source a part (thanks Mike!) & he recommended I contact Vulcan, which I did. Their recommendation was the Draw Straw I, which is made to replace my rusted out part on the module lid; no drilling extra holes in the tank. I also ordered the big line kit & will be relocating my Airtex replacement pump down onto the frame rail next to the tank. The big line kit also includes elbows & hoses to replace the rigid line & banjos between the OEM filter & the injection pump. The injection pump elbow has a tap for a fuel pressure gauge to monitor pressure at the VP where it counts. I'm expecting delivery later this week.In the mean time I have plenty of work to do. After cleaning all the grime off the tank exterior with Purple Power & a scrub brush, I was able to do a pressure test of my tank to ensure that the filler & vent fittings were not leaking. Note: A Cool Whip container fits the module opening in the tank perfectly & allows the locking ring to screw down & seal off the big hole for a pressure test. My truck was originally owned & operated in up-state New York and it has seen it's fair share of salty roads - corrosion control is in order. I spent some time Saturday/Sunday adding doublers to the forward tank strap which had almost rusted through. And I have a new set of 1 3/16" bore rear wheel cylinders to install. I will update this thread with pictures as time permits.Joe in St Louis

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This past Saturday I installed the pump relocation kit & the Draw Straw I. The parts showed up on Friday afternoon. I called Vulcan because there were lots of questions that could not be answered by the instructions. There was adequate hose in the kit to relocate the pump as per the installation instructions, but I also wanted to run a hose from the Draw Straw to the inlet of the fuel pump. Since there wasn't enough hose to do this I improvised as follows;1) I cut a 15" piece of hose & made up the section between the filter outlet to the injection pump as per the Big Line Pump Relocation System instructions using the supplied adapters & Push-Lock fittings. I left the fuel pressure gauge tap installed where it was in the filter lid.2) I cut a 30"-36" piece of hose & made up a section to install between the filter & the forward end of the OEM steel supply line. I used the supplied adapter & Push-Lock elbow at the filter inlet. I cut off the OEM hose from the end of the supply line and I slid the new hose over the steel supply line, securing with a hose clamp.3) I installed the mounting bracket & fuel pump onto the inboard side of the frame rail as per the instructions. I cut the OEM steel supply line in two places (before & after the pump) and used two sections of hose (1 foot each) to connect the pump inlet & discharge to the steel line. I used the supplied fittings for the pump connections & used hose clamps to secure the hoses to the steel line.4) I removed the OEM supply & return hoses that were installed between the fuel tank module & the steel lines. I replaced them with 18" sections of hose to facilitate easy hook-up while the tank was on the ground. Please realize I'm doing this in the driveway with the rear of the truck jacked up, rear wheels about 10" off the ground to allow enough clearance to pull the tank out from under the truck - less than ideal conditions. The hoses I installed are much longer than the OEM ones but I didn't think it would cause a problem. At the Draw Straw head I used the included 3/8" MPT x 3/8" hose Push-Lock fitting on the suction port & a standard 1/4" MPT x 5/16" hose barb with clamp on the return.. The secondary return port was sealed with the included 1/4" plug.I installed the tank, poured in some fuel, bled the air out of the system at the filter inlet, then did two bump cycles to prime the injection pump - it started right up. I noticed that fuel pressure seemed a bit higher, showing 20 psi with engine not running & 17+ at idle - all looked well. But when I took the truck for a test ride I noticed the fuel pressure dropping significantly; easily dropping to 12 psi in town and down to 5 psi when applying WOT while at 60 mph cruise. This is with about 10-12 gallons of fuel in the tank. Prior to the pump relocation work I was seeing 16 psi at idle and a low of about 14.5 psi in all driving conditions. In March of this year I hauled a 10k 5th wheel for about 120 miles on the interstate through the Flint Hills & never saw the fuel pressure drop below 14. I've been doing some research and is appears these symptoms indicate that there is a restriction somewhere between the fuel tank pick-up & the pump. This seems somewhat strange to me because it looked as though fuel was flowing very well when I was bleeding air out of the system from the filter outlet into a bucket. Interesting to note that when I was bleeding the system the rear of the truck was still up on jack stands and I had only poured in about 7 gallons of fuel, indicating that the fuel pick-up was working well. But since pressures were fine before the relocation a restriction seems like the logical problem. Another possibility is perhaps the old filter-to-injection pump set-up was restricting fuel flow enough to give a false fuel pressure indication. I was thinking of re-installing the old set-up to see if it returns the previous gauge indications. A restriction may have been caused while raising the tank into position. After I secured the tank to the chassis I reached up to check the routing of the supply & return hoses. Since they are about 12" longer than the OEM hoses they rotated the Draw Straw head around as the tank went up into position. I tried to ensure that there were no kinks in the hoses but I did not get a visual due to lack of access. Since the installed location of the Draw Straw tube is not centered in the fuel tank module, I'm not sure what sort of problem may have resulted from rotating the head.With regard to the Draw Straw I, it sure seemed a little loose when installed into the lid of the fuel tank module. I put some liquid hand soap on the barb & it pushed into the grommet pretty easily. I'm concerned that fuel will seep out between the head of the Draw Straw & the grommet. That would be a huge disappointment seeing that the problem I was trying to eliminate in the first place was a leak at the module caused by a rusted out fuel tube assembly. Suspecting there is a restriction between the tank & the lift pump, I plan on dropping the tank again. I will remove the module & inspect to ensure there is no problem with the fuel pick-up. I may try to devise some sort of clamp arrangement between the tank vent & the supply line to prevent the Draw Straw head from rotating during installation. I'd like to convert the existing kluge to a single section of hose between the Draw Straw & the fuel transfer pump , possibly increasing the diameter from 3/8" to 1/2".I'll keep you posted.Joe in St Louis

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I don't have my pictures downloaded yet, but I came across these photos from a fellow on the TDR who installed one in his truck. Good write-up. http://www.turbodieselregister.com/user_gallery/displayalbum.php?userid=8327&albumid=18623 It should be noted that there are a number of different configurations of the module out there - I think I've seen about 3 so far. This fellow's module is identical to mine. His truck is a '99, just like mine. In the 11th picture you will see the fitting that was rusted out on my unit that caused the leak - looks like he was having the same problem. The 15th picture is looking into the bottom half of the module (basket) with all of the guts removed - see last picture for the guts. OEM basket has only the one hole in the center. Vulcan instructs to open up the center hole for the pick-up tube of the draw straw to pass through & drill the 2 extra holes on either side to facilitate quick return flow from the basket down to where the pick-up tube terminates - he's already drilled the holes. Vulcan recommends cutting the end of the pick-up tube at an angle. All of the removed components in the last picture were designed to remove as much fuel out of the tank as possible without cavitating the pump. The gray stem plugs into the red strainer assembly shown at the bottom right of the picture; the end opposite the black suction line fits into the strainer. The strainer fits snugly inside the bottom of the basket. The oval bracket supports the stem at the suction line end to keep it centered in the basket & plugged into the strainer. The brown circular part pictured below the stem is a float which is housed inside of the red strainer basket on the bottom (shown in the 12th picture), forming the lower chamber of the module. I have found no detailed principal of operation for the module, but the following is the way it seems to be designed. The system pick-up point is at the bottom of the gray stem inside the basket, not in the lower chamber where the float is located. The strainer connected to the stem is to strain the fuel that flows down from inside the basket into the fuel pick-up (end of the stem). Fuel in the basket is replenished by the return flow from the injection pump/injectors & what spills into the basket at higher fuel levels. Fuel can also be drawn past the strainer basket into the lower chamber, up through a port in the center of the float & up into the bottom of the basket. At very low fuel levels the float acts like a skimmer. It rides on top of the fuel, allowing fuel to be drawn from a large area & prevents air from being drawn into the bottom of the basket. I'll have to trust that this design was effective even if it is not intuitively obvious. Vulcan's solution (removing the guts) basically eliminates any in-tank straining capabilities of the OEM design. They recommend the installation of an external 140 micron strainer in the supply line prior to the fuel pump. Their solution also eliminates the low tank skimming function of the OEM design for whatever that was worth. Vulcan's solution is not to run the tank below 1/4 -1/8 full. Kind of reminds me of the old joke "Doc, it hurts when I do this", and the reply "Well, don't do that!". The installation instructions state to put the straw through the center hole of the basket. When installed into the lid of the module the head of the draw straw is not centered over the basket, so the straw goes down at an angle. Since the straw is a rigid nylon tube , this angle tilts the head of the Draw Straw, preventing it from sitting flush on the grommet. I saw this as a possible problem leading to a leak, especially since the head was not a tight fit into the grommet. Confident that I knew a better way, this is where my BOMB began. Unfortunately I did not realize Vulcan recommended an external strainer until I read the installation instructions, after the parts were delivered. So I decided to make changes to the draw straw installation so I could retain the OEM return strainer. I used a heat gun to make the straw flexible so that I could put an S curve in it to align with the hole in the bottom of the basket. I cut off the ends of the gray stem, bored them to fit snug over the straw to be used as bushings, and used a piece of 3/4" copper as a spacer between the bushings. I refitted the red strainer into the bottom of the basket, passed the straw through the strainer, seated the lower bushing into the strainer, slid the oval bracket over the top bushing & secured it into the basket. All these mods mimicked the OEM design with the exception that the straw extended into the bottom chamber of the module. I wanted to retain some of the skimming function of the float in the lower chamber. I bored out the port in the center of the float to fit snugly over the end of the draw straw; once pushed onto the straw it would not move. Instead of cutting off the end of the straw at an angle I left it square, but cut four semi-circular arches through the side and at the end of the tube. I made these arches about 1/4" in diameter, figuring they would flow plenty of fuel to keep up with my Airtex pump. The decision to retain the float may be the source of my current fuel pressure problems. As described in my last message, the draw straw rotated in the tank module lid as I was lifting the tank into position on the chassis. Since the straw is now S-shaped it's possible that rotating the draw straw caused the float to fall off & block the end of the straw, causing a restriction. My plan is to drop the tank, remove the module & inspect. I'll report back when I make some progress.

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you need to drill out your basket. when i ran the OEM canister with my FASS is saw a similar issue as you are having, my problem was the fuel pump was sucking the fuel faster then the fuel could come into the basket, luckily the fass returns most of the fuel into the tank, right into the basket actually.2. i wouldn't have heated any fuel lines up, went through that mistake as well, the lines lost their regitity and ended up increasing restriction under wot.3. i would run larger fuel lines and if possible i have found that USCG approved diesel fuel line does not get smaller over time when run against a larger pump like a fass95.

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Sorry for the late response - been tied up for the last 10 days.[ATTACH=CONFIG]2873[/ATTACH][ATTACH=CONFIG]2875[/ATTACH][ATTACH=CONFIG]2874[/ATTACH][ATTACH=CONFIG]2847[/ATTACH][ATTACH=CONFIG]2848[/ATTACH][ATTACH=CONFIG]2849[/ATTACH]This is my fuel module removed, the source of my fuel tank leak, and the module guts exposed when the basket is removed. Click on the pics for a larger view.[ATTACH=CONFIG]2850[/ATTACH][ATTACH=CONFIG]2851[/ATTACH]These pics show the new Draw Straw I installed into the lid & how the nylon straw was reshaped (using heat gun) so it would be centered in the basket. The anodized head has a barb machined into it so that installation is just a press fit into the OEM grommet. The nylon straw is very rigid & tight onto the anodized head. It took quite a bit off heat before it would yield to an S-bend. No reasonable amount of force could cause it to collapse.[ATTACH=CONFIG]2852[/ATTACH]This shot is looking under the lid of the module where the Draw Straw passes through inside the tank. The fit of the head into the grommet was on the loose side. It could slide up & down about 1/16" - 3/32", and its fit in the grommet could have been tighter for my liking. I was able to stretch a nitrile o-ring over the base of the head & stuff it in between the barb & the grommet which tightened things up both axially & laterally.[ATTACH=CONFIG]2853[/ATTACH][ATTACH=CONFIG]2854[/ATTACH][ATTACH=CONFIG]2856[/ATTACH][ATTACH=CONFIG]2855[/ATTACH][ATTACH=CONFIG]2857[/ATTACH][ATTACH=CONFIG]2858[/ATTACH]These pictures show how the guts of the module were modified to work with the large diameter straw, and how the basket was modified with a larger central hole (for the straw), two holes on either side of the center one (to allow fuel in the basket to flow down into the lower chamber where the straw end is located), and holes in the sides of the basket as recommended by Vulcan. Note that fuel migrating from the basket to the lower chamber has to pass through the red circular strainer on the bottom of the straw. The strainer is a push fit into the bottom of the basket, and the lower bushing on the straw is a tight fit between the straw & the strainer - no fuel can pass between these joints.[ATTACH=CONFIG]2861[/ATTACH]This shows the Airtex transfer pump relocated from the OEM location on the engine to the inboard side of the left frame rail, just forward of the fuel tank. All fittings, hose, pump mounting bracket, and harness extension were included in the Vulcan Pump Relocation Kit. The rubber stand-offs I pulled out of my "20 year jar". Very quiet operation.[ATTACH=CONFIG]2859[/ATTACH]I replaced the OEM nylon supply & return lines at the tank with good quality Parker hose supplied by Vulcan. I left them long to facilitate easy installation.[ATTACH=CONFIG]2860[/ATTACH]Here is the top of the tank after installation. You can see the excess length on the hoses found a natural curve, but caused the head of the Draw Straw to rotate 45-60 deg. ccw. This rotation caused the straw to rotate inside the basket due to its tight fit onto the head. I thought this might have screwed something up between the straw & the basket, contributing to the lower fuel pressures I was seeing after installation.To be continued...Joe in St Louis

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Don't know why the first three pics failed to display. Let's try this[ATTACH=CONFIG]2862[/ATTACH]Module removed from tank[ATTACH=CONFIG]2863[/ATTACH]Source of fuel tank leak[ATTACH=CONFIG]2864[/ATTACH]Module with basket removed showing the guts.

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After I installed the new Draw Straw & Transfer Pump Big Line Relocation Kit I took a test drive & found my fuel pressure had dropped dramatically from where it was before I did the work. I figured was either a problem was either a restriction between the tank & the pump, a bad pump, or that previously I was getting a false reading on my FP gauge due to restrictions caused by the OEM fuel line/fittings between the fuel filter & the injection pump. After much moaning & gnashing of teeth I decided to drop the tank & rework the hoses & Draw Straw installation. If that didn't fix it I figured the problem was with the pump.I dropped the tank a second time & pulled the module. I didn't really find anything out of order with the straw & the basket, but I removed the float from the lower chamber & cut the end of the straw at an angle.[ATTACH=CONFIG]2876[/ATTACH]This pic shows the module inverted & with the lower strainer removed. You can see the suction end of the straw with it's end cut at an angle.[ATTACH=CONFIG]2866[/ATTACH][ATTACH=CONFIG]2877[/ATTACH]I had a pile of this tough nylon anti-chafe sheathing I'll call "snake skin" which I found in a dumpster about 15 years ago. I installed over all the hose. Note the third port on the Draw Straw head which I have plugged. An AD II would use this port as the return to the tank.[ATTACH=CONFIG]2867[/ATTACH][ATTACH=CONFIG]2868[/ATTACH]These pics show an external support bracket I made up to prevent the Draw Straw from rotating during tank installation. Adel clamps sourced from the 20 year jar, left-overs from my Sabreliner mechanic days.I got a new piece of 3/8" Parker Superflex hose from Vulcan so I could remove the jury rig I had tried in the first installation. [ATTACH=CONFIG]2869[/ATTACH][ATTACH=CONFIG]2870[/ATTACH]The picture on the left was taken just prior to installing the tank the 2nd time. It shows the new suction hose from the tank to the pump, supported under the frame rail by zip ties. The snake skin has a smooth surface and easily slid through the zip ties when jacking the tank into position to take up the extra slack. When the tank was installed I pulled up the slack & connected the other end to the transfer pump. The return hose on the right ended up kinking when the tank was up in position (see pic on right) so I ended up cutting the rigid return line just to the right of the frame support clip. With the return hose clamped on in the new position there was no kink and all is well.After everything was buttoned up I took another test ride - no improvement. Fuel pressure was still dropping below 12psi in town, and falling away to 5 with WOT. Bummer. Next step was a new pump. Bummer. Then it dawned on me - I purchased my pump at my friendly neighborhood Advance Auto Parts last Thanksgiving, and it came with a 1 year warranty. I called them up, they had one in stock, and would honor the warranty. I removed the old pump & they swapped it for a new one, free of charge. Schweet! Now pressures are holding 18 psi at idle, 15+ psi in town & at cruise on the highway. Schweet! It will drop down to 13.5 at WOT, but that is something I can easily avoid. Can't afford to fill the tank yet, but I'm pretty confident the Draw Straw is adequately sealed to the module lid so I shouldn't have a problem.Why did the pump go bad? Must have sucked up some swarf on initial start up after the mod. Why are the pressures slightly lower than before the pump relocation? Must be the result of less restriction between the filter (where my FP gauge is tapped) & the injection pump. I'm not worried about it - fuel flow cools the pump, not pressure.Sorry for the long story. Hope it helps someone else.Joe in St Louis

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Here are the first two pics from above post. Not sure where the problem lies.[ATTACH=CONFIG]2871[/ATTACH][ATTACH=CONFIG]2872[/ATTACH]

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Why did the pump go bad? Must have sucked up some swarf on initial start up after the mod. Why are the pressures slightly lower than before the pump relocation? Must be the result of less restriction between the filter (where my FP gauge is tapped) & the injection. I'm not worried about it - fuel flow cools the pump, not pressure. Joe in St Louis

Can't have flow without pressure. After doing the studying of the overflow valve by the time you get to 10 PSI the overflow valve is completely closed so flow is gone except for the flow to the injectors. Now if you coasting there is little to none. So at 14 PSI the flow will keep the VP44 cooled and lubed properly.

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The lid of the module holds four components; the level sender electrical connector, the fuel suction/return lines, the roll-over valve, and an unused capped-off extra fuel line. Each one of these components is plug-shaped, about 1" in diameter, & is seald onto the lid with a rubber grommet. My problem was that the fuel suction/return line component had rusted through; not the lines themselves but rather the sheet metal that formed the plug & supported the lines.While installing my AD150, I also found the suction/return lines were rusted. The AD came with the draw straw that goes in the tank, not the basket so I'm only using the stock line for the return. Its not leaking now but its pretty weak. Does Vulcan or someone make something for this?

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While installing my AD150, I also found the suction/return lines were rusted. The AD came with the draw straw that goes in the tank, not the basket so I'm only using the stock line for the return. Its not leaking now but its pretty weak. Does Vulcan or someone make something for this?

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While installing my AD150, I also found the suction/return lines were rusted. The AD came with the draw straw that goes in the tank, not the basket so I'm only using the stock line for the return. Its not leaking now but its pretty weak. Does Vulcan or someone make something for this?

Yes, the Vulcan Draw Straw I replaces the stock steel fitting on top of the module. It has an anodized aluminum head equipped with barbed fitting on it's base that fits into the OEM grommet that sealed the steel fitting. The DS has 3 ports: one 1/2" suction & two 1/4" returns. I found that the head was not real snug in the grommet, so I fitted an o-ring between the barb & the grommet on the underside of the module top to tighten things up. I had pics in my write up but they vanished after some server event a couple weeks ago & I can't post pics back into this thread. I'll try to post them in a new thread.

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