Need help with fuel pick-up for FI SBC

[TQJ CJ5]

UPDATED (pg 2 pics): In tank fuel pick-up's for FI SBC

Vehicle: 1980 CJ5
Engine: '96 LT1 (mildly tweaked per PO)

I've recently scrapped the OEM fuel tank and placed an RCI fuel cell in the back of the Jeep's bed above-board. I was hoping to use the Walbro multi-point fuel pick-up's as they seem like a great solution to low fuel/steep climb or descent scenarios that might cause fuel starvation. However, I've developed a concern about the set-up.

The RCI cell's fuel pick-up tube coming from the -8AN port up top is 1/2" (logical since -8AN is 1/2" OD for hard line). Unfortunately, the multi-point pick-ups are designed to work with 5/16" submersible fuel hose. I've ordered the necessary parts to add a -6AN bulkhead fitting to the cell and run the 5/16" hose off that to the in-tank pick-up's. My concern lies in the fact that the PO used 3/8" line from the OEM fuel tank to the motor and this causes me to wonder if 5/16" hose and hard lines in the tank are going to be too restrictive. When I visually compare the 3/8" hardline I have to the 5/16" hard line I was planning to use in the tank, the ID is considerably different. Since I'm not a fuel system expert, do ya think this difference will cause me any problems (i.e. insufficient fuel flow/volume)?

Note: the fuel line from the top of the bulkhead fitting would be 3/8" going to an OEM LT1 fuel filter and then to a Bosch (#0 580 254 984) in-line fuel pump to the motor.

Any input would be greatly appreciated.

 

[Binder]

I would not use a multi point pickup for the reason you mentioned and yes, 5/16" is too restrictive.

 

[TQJ CJ5]

Binder,

If you were to predict the likelihood of complete fuel starvation due to steep ascent or descent or off-camber driving based on the design of these RCI tanks and their 1/2" fuel pick-up tube that sits about 1" off the floor and almost centered left to right/maybe 3" off the wall(in my case toward the rear of the vehicle), what would you say?

If I wanted to use the existing 1/2" aluminum fuel pick-up tube that is welded into the RCI bulkhead fitting, is there any alternative way to pull fuel from multiple points in the tank? (since the only submersible fuel line that I've found thus far is 5/16" and the only fuel pick-up's I've found are designed for 5/16" hose)

Thank you...

Terry

 

[TQJ CJ5]

Okay, I've just spoken with one of the techs at FuelSafe who assured me that running the 5/16" hard line, hose and 2 pick-up's in the tank up to the -6AN bulkhead fitting and then 3/8" from there to the filter, pump and motor will be sufficient up to around 500+ HP. The filter and pump will sit below and relatively close to the fuel cell so having fuel ready for the pump to push (apparently one of the best pumps in the world for pushing fuel; Bosch) to the motor should not be a problem.

I think I might give it a try. If it doesn't work well, I'll just use the 1/2" pick-up tube that is part of the RCI tank

 

[Binder]

No fuel pickup system is perfect, there's always going to be a angle at which it will suck air. By going with multi pickups it just makes it worse as there is now twice the chance of one of them getting out of the fuel and sucking air......3/8" is technically the minimum size fuel supply line for GM systems. Going with 5/16" may work but I would be suprised if it doesn't effect your fuel pressure to some degree.

 

[TQJ CJ5]

I hear what you're saying...

A little about these pick-up's (from Auto Performance Engineering's website):
These fuel pickups were originally developed for snowmobile applications, but they work great in rock-crawlers or in fuel tanks that don't have baffles. These are the same type of pick-ups that are in the Holley Universal In-Tank Mulit-Point Fuel Pick-up Kit [Holley part number 12-951 - two pickups per kit]. Walbro made those pickups for Holley.

The original Walbro pickups were the MP-10. Those were the pickups in the Holley kit, too. Those pickups had a 30 micron screen. With fuel formula changes in recent years, the snowmobile manufacturers were noticing a type of goo building-up on the pickups. That goo was the new fuels reacting to the plastic fuel tanks. Walbro changed the mesh to 70 microns and there was no more buildup on the pickups. . The new part numbers are MP-12 thru MP-16.

How they work:
Have you ever sprayed water on a window screen? Recall that the screen will actually hold some of the water. These pickups work the same way. When the pickup is submerged in fuel, gas will pass through the mesh with ease. When fuel sloshes away from the pickup, the mesh will hold enough fuel to fill all the tiny holes. That mesh full of fuel acts like a solid. At this point, the pump, sucking on the outlet will cause the mesh to suck shut, preventing the pump from sucking air. When fuel covers the pickup once again, the valve will open up and transfer fuel.

These pick-ups have one or two 5/16 fittings. The pickups with two fittings can be used to connect pickups in series.

Walbro suggests that at least one pickup in the system should have a bleed hole. If your system doesn't have a bleed hole, it can become totally closed if all of the pickups close at once. If that happens, the closed pickups can take several minutes to re-open, depending upon how much vacuum the fuel pump has pulled.

The inlet side of the pickup has a 70 micron mesh. The pickup is just under three inches in diameter and just under two inches tall. These pickups have been tested in gasoline to -40 F and in diesel fuel to 0 F.


Re: fuel pressure being affected... Would the critical pressure(that which is going to the motor) be affected negatively even if the fuel line after the strong Bosch fuel pump is 3/8"? Are you saying that because of the reduced diameter prior to the bulkhead fitting on the fuel cell, that the pump may not have enough fuel coming into it to produce the ideal pressure for my motor?

(again, I'm not an expert but just trying to weigh the various input I've been receiving)

 

[Binder]

Re: fuel pressure being affected... Would the critical pressure(that which is going to the motor) be affected negatively even if the fuel line after the strong Bosch fuel pump is 3/8"? Are you saying that because of the reduced diameter prior to the bulkhead fitting on the fuel cell, that the pump may not have enough fuel coming into it to produce the ideal pressure for my motor?

(again, I'm not an expert but just trying to weigh the various input I've been receiving)

Sounds like quite a system for the pickup, I guess just try it and find out.
Typical inline pumps don't make any vacuum at all. That's why it's important to mount it below the level of the fuel so the siphon effect will keep fuel to the pump. Also typically in this type of system having a 5/16" section of line after the pump in the pressure section would be enough to reduce fuel pressure/ volume. Having a reduction before the pump they are even more sensitive.
I'm no expert here either, just a hobbyist like everyone else but I have experience with quite a few different applications of these systems. None of this means that it won't work but just what has happened to other systems. Like I said before, just try it and find out.:awesomework:

 

[crash2]

5/16 to 3/8 --in a fuel starvation your talking about alot of fuel pumping---you won't have any issue with the 5/16..

Alot of the high output jap stuff run 5/16 (metric equivilant) and pump alot of fuel with zero problems

 

[Totalled]

Yeah, all FI Fords use 5/16 for the supply and return line.. 2.3L-7.5L. Should be fine.

 

[Binder]

I would be interested to hear the results from this. Do you have a fuel pressure gage that you can see when driving? If yes, post up the results especially under high load/ high RPM's.

 

[TQJ CJ5]

I don't have a fuel pressure guage installed but I can certainly post if there was any negative affect or if I have any problems with my set-up.

Thank you all for responding and providing a little additional reassurance.

Note: w/ a little assembly lube I was able to stuff the 3/8" aluminum fuel line into the 5/16" hose. therefore, only the lines at the bottom of the tank will be 5/16" and the pick-up tube from the top of the tank to the 5/16" network will be 3/8". From the bulkhead fitting at the top of the tank to the filter, to the pump, and then to the motor will all be 3/8" and -6AN fittings. Fuel filter and pump will sit below the tank, mounted to one of the frame crossmembers.

 

[Binder]

I don't have a fuel pressure guage installed but I can certainly post if there was any negative affect or if I have any problems with my set-up.
[/IMG]

But keep in mind that there can be negative affects without you knowing it right away. These are learning systems that will adapt to a small amount of fuel inconsistancy. It will seem to run fine but if you have for instance a O2 sensor go bad it will go into open loop mode and the "learn" will not be used. At that point it may run bad or not at all when if everything is set up correctly your engine will run just fine with no O2.
Just some food for thought, Good luck with it.:awesomework:

 

[TQJ CJ5]

I'll look into a FP guage

 

[TQJ CJ5]

In case anyone's interested, here is the final product

I wanted to see how everything would fit together before I modified the RCI fuel tank and threw this little system in.

Let me know what you think...

Oh, and I ordered a fuel pressure gauge with an isolator so I can monitor the pressure from inside my Jeep (just for you Binder

 

[Binder]

Oh, and I ordered a fuel pressure gauge with an isolator so I can monitor the pressure from inside my Jeep (just for you Binder

:haha: Don't do it for me, it's just my opinion. You can build your rig any way you want.:cheer:

 

[TQJ CJ5]

nah, I was just throwin ya a friendly little jab... actually, the more that I thought about it, having the ability to know what's goin on with the fuel isn't too bad an idea. I do appreciate your input.

 

[crazybluerider1]

Any updates on how this system is working?