- Joined
- Jul 21, 2006
- Messages
- 2,756
I have an NWMP tank that is about 15+ years old and, for the most part, has served me well except when it comes to any angles off-road that do not favor the pickup which is located on the forward wall on the driver's side. It takes very little nose up passenger side down angle to uncover that pickup. The BC Broncos large accumulator did a lot to alleviate running dry but I have found I am spending more time on obstacles than the capacity of the accumulator will support. This past November at Uwharrie was the straw that broke the camel's back. I winched a buddy off an obstacle and couldn't start the Bronco as the pickup was uncovered and the accumulator had run dry. I immediately went home looking for alternative solutions which included buying a new tank with in-tank pump, modifying the NWMP tank for in-tank pump, installing the Holley fuel mat, or going with the Walbro pickups.
The new tank was cost prohibitive and neither that nor installing an in-tank pump seemed to make sense as I could easily see me getting into a situation where I could uncover the pump. Plus, changing a rail mounted pump in the field is fast and easy as opposed to in-tank. The fuel mat is expensive and they didn't offer a size that properly accommodated this tank. So, in the end, I was left with the Walbro pickups.
Walbro Pickups (MP-12) $104 4ea http://www.autoperformanceengineering.com/html/pickups.html
5/16 ID J30R10 hose $20 1' http://apeusa.com/html/kits.html#fuelhose
3/8 ID J30R10 hose $20 1' http://apeusa.com/html/kits.html#fuelhose
stainless #4 hose clamp $3.00 5ea http://apeusa.com/html/kits.html#fuelhose
RE cup magnets $14.99 5ea https://www.amazon.com/Earth-Neodym...20308&sr=1-12&keywords=Neodymium+Round+Magnet
5/16 galvanized steel tube $36 6' Local hose supply
Permatex 80019 $8.69 1ea https://www.amazon.com/gp/product/B000HBM3QQ/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
3/16 cork gasket sheet $5.50 1ea ACE hardware
Sealed rivnuts $12.35 25ea https://www.mcmaster.com/#98280a340/=16fuq8n
Aluminim spacers $8 5ea ACE hardware
5/16 compression tee $16 2ea ACE hardware
1/4 FPT tee $8 1ea ACE hardware
1/4 MPT - 5/16 tube comp fitting $4.00 2ea ACE hardware
1/4 MPT - 3/8 barb $4.00 1ea ACE hardware
Screws, washers, lock washer, nuts $15 ACE hardware
Loop clamps $8 5ea Local hose supply
16ga galvanized sheet metal (6"x12") FREE 1ea Buddy
TOTAL = $288
Started by draining and rinsing the tank with water a couple times and then used some Dawn dish soap for good measure. Took less than 30 minutes and didn't have to worry about fumes.
I really wanted to take my time and do this right so I made a mock tank out of cardboard to test for proper placement of the access holes to ensure I would be able to reach all four corners of the tank as well as over the top of the baffle. I really need to get a life...working on it.
I want to give nvrstuk credit and thank him for his advice in suggesting I go with two access holes rather than one. I cut two 4.5" holes in the tank so I could access both sides of the baffle as well as use two arms to position and work inside the tank. This was based on the size of my arms so I suppose other folks may need to cut larger holes. The tank is 16ga so I made the cover plates out of 14ga and installed twelve 10-32 sealed rivnuts on each hole which has them spaced out about 1.12" all the way around. This really makes a huge difference being able to get both arms in the tank. I did make things a little close in tolerance by only allowing ¼” from ID to OD from the rivnuts. I would recommend ½” instead because stuff moves as you can clearly see.
Placement of the front two pickups was a no-brainer as they clearly should go in the front two corners. The rear two pickups were the subject of some debate. Do I place them at the base of the incline just aft of the baffle or do I place them further back at the top of the incline?
As you can see in this picture, the baffle is represented by the vertical blue tape covering the corner and the potential location options of the rear pickups are represented by the blue tape labeled 1 and 2.
In this picture you can see that even at 60 degrees nose high with 1 gallon of fuel (depicted by the new area of blue tape covering the corner), the rear pickups, if positioned just behind the baffle at position 1, would become uncovered leaving me high and dry (pun intended). Utilizing position 2 will prevent this from happening.
The nature of the Walbro pickups requires them to be wet in order to close when they become uncovered. So then the question becomes what if I employ position 2 and my fuel level is below the rear pickups on startup? Won't they just suck air if they can't close? The answer is no. This is because they are on a raised 30 degree angle relative to the two front pickups and since air rises and is less dense than fuel, the system will naturally pull only gas from the front pickups rather than pull air down from the rear pickups. Plus, all I need is 3.4 gallons of fuel (about 1/8 tank) on level ground to cover those rear pickups.
I was hesitant about using submersible fuel line as I had read reports of folks experiencing failures similar to non-submersible rated line. Some concluded this was possibly due to fuel entering the internal structure of the line at the end where it is cut and the protective coating is no longer present. Since the Walbro pickups are plastic and terminate to a nipple, using hose was my only option. I decided to use Aviation Gasket to coat the ends of all my submersible tubing in an effort to protect it from possible future damage. Now I will caution you, this stuff is nasty, makes a hell of a mess and takes FOREVER to even remotely tack. Depending on how thick it is applied, you could be looking at 48 hours to be able to handle it without it getting on everything.
In order to minimize the amount of submersible hose, I used 5/16" steel line as the primary structure and only used submersible hose as a connector between the 5/16" steel line and the Walbro pickups. The added rigidity of the steel line gives me peace of mind knowing it won't be affected off road.
As for securing the structure inside the tank, I went with RE magnets with #6 screws attached to standoffs and clamps. This provided the correct heights and a super secure solution.
I have seen multiple designs for these systems. Most either run a single series circuit or a tied parallel design like what I went with. The parallel design provides more redundancy should a pickup fail.
Having the Tees on each side and in the middle of the cross tube made the system more modular and eased installation. The pickups are 3" in diameter and they do not easily slide through the notch in the baffle as it's hypotenuse is 3" as well. Being able to split the section in half and eliminate the need to coax the pickup through the notch made things super easy. I used Aviation Gasket as a thread sealer on the three fittings for the cross tube tee going to the pickup as Aviation Gasket is really the only choice in gasoline. Apparently PTFE tape or pipe dope deteriorates in fuel or can cause injector clogs.
As you can see in the picture below, I did run into an issue when I installed the cross tube as I failed to account for the sending unit and sure enough the float ended up right on top of the cross tube. The sending unit flange bolts are clocked thus preventing it from being rotated so I was left with no choice but to move the cross tube aft a few inches in order to clear the cross tube. After fixing that snag I worked out how I was going to get the gas out of the tank.
Some folks just block off the old pickup and use a bulkhead connector. I just didn't see the advantage of drilling another hole in this tank unless I was looking to have fancy -AN fittings. The pickup tube was welded to the bottom of the tank all the way at the tip so there was no way I could get a piece of 3/8" submersible hose attached to the end. I looked at grinding the weld and cleaning the tube enough to accept the hose, but not even my Dremel could get in there well enough so decided to cut a 4" section out of the old pickup and slide the submersible line onto it secured with a hose clamp. My new concern was adding stress to the pickup tube as it was now only secured via one weld where it exits the tank. In the end, I felt it would be okay as the wall thickness of the tube NWMP used was pretty significant and their weld was more than sufficient.
Once I triple checked everything inside the tank for security and contamination, I made my own cover gaskets out of cork and coated them on both sides in Aviation Gasket and torqued the cover plates carefully. I sealed all the ports except the pickup and applied 10psi to the tank just to make sure my cover plates weren't going to leak.
Everything seems to be working great but that is just on the street. Won't know much beyond that still I go to Windrock at the end of March but I have a feeling things are going to be smooth sailing in the fuel delivery department from now on. I will need to make sure I change my fuel filter in the next few hundred miles. Although I was pretty meticulous in removing any contaminants from the tank, I think it just makes sense to change it.
So I have two questions...
1.) Can anyone see any possible justification to continue to run the BC accumulator now? I mean, at this point, it is just a fancy last chance fuel filter rather than an accumulator.
2.) What about continuing to run a LP pump to supply the HP? I wonder if I can just get rid of the LP all together. Here are my thoughts on the subject and why I am struggling to make a decision. As I stated earlier, the Walbro pickups need to be wet initially in order for them to operate correctly and close when uncovered. Now, in a situation where the tank is sucked completely dry, all four pickups will close and not reopen unless the vacuum is relieved by cracking open a line or a bleeder pickup is used. I chose not to employ a bleeder pickup so, assuming all my connections are leak free, I should never lose prime on the system IF there is a check valve in the fuel pump. If there is not a check valve in the HP pump, the fuel can bleed back into the tank over time but I am not sure where the air would come from assuming the pickups are covered. Am I just overthinking this? The injectors are closed and the return line shouldn't have air in it. Hmmmmmm.
Here are some pics of all four corners and the center.
The new tank was cost prohibitive and neither that nor installing an in-tank pump seemed to make sense as I could easily see me getting into a situation where I could uncover the pump. Plus, changing a rail mounted pump in the field is fast and easy as opposed to in-tank. The fuel mat is expensive and they didn't offer a size that properly accommodated this tank. So, in the end, I was left with the Walbro pickups.
Walbro Pickups (MP-12) $104 4ea http://www.autoperformanceengineering.com/html/pickups.html
5/16 ID J30R10 hose $20 1' http://apeusa.com/html/kits.html#fuelhose
3/8 ID J30R10 hose $20 1' http://apeusa.com/html/kits.html#fuelhose
stainless #4 hose clamp $3.00 5ea http://apeusa.com/html/kits.html#fuelhose
RE cup magnets $14.99 5ea https://www.amazon.com/Earth-Neodym...20308&sr=1-12&keywords=Neodymium+Round+Magnet
5/16 galvanized steel tube $36 6' Local hose supply
Permatex 80019 $8.69 1ea https://www.amazon.com/gp/product/B000HBM3QQ/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
3/16 cork gasket sheet $5.50 1ea ACE hardware
Sealed rivnuts $12.35 25ea https://www.mcmaster.com/#98280a340/=16fuq8n
Aluminim spacers $8 5ea ACE hardware
5/16 compression tee $16 2ea ACE hardware
1/4 FPT tee $8 1ea ACE hardware
1/4 MPT - 5/16 tube comp fitting $4.00 2ea ACE hardware
1/4 MPT - 3/8 barb $4.00 1ea ACE hardware
Screws, washers, lock washer, nuts $15 ACE hardware
Loop clamps $8 5ea Local hose supply
16ga galvanized sheet metal (6"x12") FREE 1ea Buddy
TOTAL = $288
Started by draining and rinsing the tank with water a couple times and then used some Dawn dish soap for good measure. Took less than 30 minutes and didn't have to worry about fumes.
I really wanted to take my time and do this right so I made a mock tank out of cardboard to test for proper placement of the access holes to ensure I would be able to reach all four corners of the tank as well as over the top of the baffle. I really need to get a life...working on it.
I want to give nvrstuk credit and thank him for his advice in suggesting I go with two access holes rather than one. I cut two 4.5" holes in the tank so I could access both sides of the baffle as well as use two arms to position and work inside the tank. This was based on the size of my arms so I suppose other folks may need to cut larger holes. The tank is 16ga so I made the cover plates out of 14ga and installed twelve 10-32 sealed rivnuts on each hole which has them spaced out about 1.12" all the way around. This really makes a huge difference being able to get both arms in the tank. I did make things a little close in tolerance by only allowing ¼” from ID to OD from the rivnuts. I would recommend ½” instead because stuff moves as you can clearly see.
Placement of the front two pickups was a no-brainer as they clearly should go in the front two corners. The rear two pickups were the subject of some debate. Do I place them at the base of the incline just aft of the baffle or do I place them further back at the top of the incline?
As you can see in this picture, the baffle is represented by the vertical blue tape covering the corner and the potential location options of the rear pickups are represented by the blue tape labeled 1 and 2.
In this picture you can see that even at 60 degrees nose high with 1 gallon of fuel (depicted by the new area of blue tape covering the corner), the rear pickups, if positioned just behind the baffle at position 1, would become uncovered leaving me high and dry (pun intended). Utilizing position 2 will prevent this from happening.
The nature of the Walbro pickups requires them to be wet in order to close when they become uncovered. So then the question becomes what if I employ position 2 and my fuel level is below the rear pickups on startup? Won't they just suck air if they can't close? The answer is no. This is because they are on a raised 30 degree angle relative to the two front pickups and since air rises and is less dense than fuel, the system will naturally pull only gas from the front pickups rather than pull air down from the rear pickups. Plus, all I need is 3.4 gallons of fuel (about 1/8 tank) on level ground to cover those rear pickups.
I was hesitant about using submersible fuel line as I had read reports of folks experiencing failures similar to non-submersible rated line. Some concluded this was possibly due to fuel entering the internal structure of the line at the end where it is cut and the protective coating is no longer present. Since the Walbro pickups are plastic and terminate to a nipple, using hose was my only option. I decided to use Aviation Gasket to coat the ends of all my submersible tubing in an effort to protect it from possible future damage. Now I will caution you, this stuff is nasty, makes a hell of a mess and takes FOREVER to even remotely tack. Depending on how thick it is applied, you could be looking at 48 hours to be able to handle it without it getting on everything.
In order to minimize the amount of submersible hose, I used 5/16" steel line as the primary structure and only used submersible hose as a connector between the 5/16" steel line and the Walbro pickups. The added rigidity of the steel line gives me peace of mind knowing it won't be affected off road.
As for securing the structure inside the tank, I went with RE magnets with #6 screws attached to standoffs and clamps. This provided the correct heights and a super secure solution.
I have seen multiple designs for these systems. Most either run a single series circuit or a tied parallel design like what I went with. The parallel design provides more redundancy should a pickup fail.
Having the Tees on each side and in the middle of the cross tube made the system more modular and eased installation. The pickups are 3" in diameter and they do not easily slide through the notch in the baffle as it's hypotenuse is 3" as well. Being able to split the section in half and eliminate the need to coax the pickup through the notch made things super easy. I used Aviation Gasket as a thread sealer on the three fittings for the cross tube tee going to the pickup as Aviation Gasket is really the only choice in gasoline. Apparently PTFE tape or pipe dope deteriorates in fuel or can cause injector clogs.
As you can see in the picture below, I did run into an issue when I installed the cross tube as I failed to account for the sending unit and sure enough the float ended up right on top of the cross tube. The sending unit flange bolts are clocked thus preventing it from being rotated so I was left with no choice but to move the cross tube aft a few inches in order to clear the cross tube. After fixing that snag I worked out how I was going to get the gas out of the tank.
Some folks just block off the old pickup and use a bulkhead connector. I just didn't see the advantage of drilling another hole in this tank unless I was looking to have fancy -AN fittings. The pickup tube was welded to the bottom of the tank all the way at the tip so there was no way I could get a piece of 3/8" submersible hose attached to the end. I looked at grinding the weld and cleaning the tube enough to accept the hose, but not even my Dremel could get in there well enough so decided to cut a 4" section out of the old pickup and slide the submersible line onto it secured with a hose clamp. My new concern was adding stress to the pickup tube as it was now only secured via one weld where it exits the tank. In the end, I felt it would be okay as the wall thickness of the tube NWMP used was pretty significant and their weld was more than sufficient.
Once I triple checked everything inside the tank for security and contamination, I made my own cover gaskets out of cork and coated them on both sides in Aviation Gasket and torqued the cover plates carefully. I sealed all the ports except the pickup and applied 10psi to the tank just to make sure my cover plates weren't going to leak.
Everything seems to be working great but that is just on the street. Won't know much beyond that still I go to Windrock at the end of March but I have a feeling things are going to be smooth sailing in the fuel delivery department from now on. I will need to make sure I change my fuel filter in the next few hundred miles. Although I was pretty meticulous in removing any contaminants from the tank, I think it just makes sense to change it.
So I have two questions...
1.) Can anyone see any possible justification to continue to run the BC accumulator now? I mean, at this point, it is just a fancy last chance fuel filter rather than an accumulator.
2.) What about continuing to run a LP pump to supply the HP? I wonder if I can just get rid of the LP all together. Here are my thoughts on the subject and why I am struggling to make a decision. As I stated earlier, the Walbro pickups need to be wet initially in order for them to operate correctly and close when uncovered. Now, in a situation where the tank is sucked completely dry, all four pickups will close and not reopen unless the vacuum is relieved by cracking open a line or a bleeder pickup is used. I chose not to employ a bleeder pickup so, assuming all my connections are leak free, I should never lose prime on the system IF there is a check valve in the fuel pump. If there is not a check valve in the HP pump, the fuel can bleed back into the tank over time but I am not sure where the air would come from assuming the pickups are covered. Am I just overthinking this? The injectors are closed and the return line shouldn't have air in it. Hmmmmmm.
Here are some pics of all four corners and the center.
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