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Old 06-18-2019, 11:03 AM   #1
gear_grinder
 
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In-Tank 105gph@40psi Pump Conversion

im an idiot and posted this in the wrong place, sorry mods

Let me preface this by saying this is my own experiment, replicated at your own risk and discretion. This modification was done to a 1996 truck, no idea if other sending units vary in design and no guarantee that the pump will fit like mine did if they're different.

I came to diesels from the tuner/hotrod scene and frankly was appalled by the cost and design of some of the aftermarket lift pumps, along with monitoring my factory lift pump (new genuine cummins and gone through the system front to back for cleanliness) pressure at various loads and throttle inputs. my stock truck with the fuel plate removed and some other minor AFC tuning would pull fuel pressure down to nearly 10psi at WOT (adjustable overflow valve idle pressure at 30psi).

So I sat down and had a think about what I needed for my new truck. I have moderate goals for the my new (to me) 1996 dually with 76k original miles 1owner truck, I'd like to make around 400whp (a common goal for many i see on the facebook groups and forums). Many people claim the stock lift pump will do 400hp when shimmed, however i have my doubts after seeing how the pressure responded to my basically stock truck. I also was shocked by the price of the name brand lift pumps (airdog/fass), absurd amount of money for the fuel flow. There has to be a better solution....

Fleece offers a dual pump in tank kit for the 4th gen trucks now, and i believe that is the best solution for them. Why are in-tank pumps the best solution for performance and efficiency? here are some reasons:

1.) No draw straws or sumps. no cutting up your factory tank and losing your factory surge tank/baffle system.

2.) Stock 3/8" fuel line will support alot of power when under pressure. 1000+turbo ls cars are running 3/8" feed line, i doubt a 400-
600hp diesel will need more.

3.) Pump cooling. 90% of what I see in people posting about failed aftermarket lift pumps are from heat. a motor working in
nothing but air needs a ton if air flow and heat sync to keep cool. liquid cools a lot better than a gas does, its why we have liquid
cooled engines and why the OEs have been sticking pumps in the fuel tanks of all vehicles for years

4.) Pump feed pressure (this one is important). your pump is feed by pressure, that pressure is atmospheric pressure pushing on the
liquid. the same way you drink through a straw, you lower the pressure on one side of the hose/tube/straw and the fluid is forced
by atm pressure to the low pressure area. Exactly the same goes for your fuel system.
Ideally external pumps need a very large feed hose, much larger than the output hose because (if they are above the fuel level)
are fed only by a fraction of the ambient air pressure. Only a fraction? Yes, to get full atm pressure (14.7psi at sea level) you'd
need to somehow draw a perfect vacuum (which is basically impossible for a fluid transfer pump). At best, usually they will
create a pressure differential of about only 1-2psi. So how can this be improved? ever do a beer bong? it works because you
not only have atm pressure on the beer, but the WEIGHT of the beer itself pushing itself into your mouth. Same goes for fuel and
your lift pumps. TANGENT WARNING! if you put your external lift pump level or below the tank of fuel and had a sump on the
tank, you could feed it with the fuel column, but nobody is going to hang their $600-1000 fass below the tank level... but I
digress.
So leading back to the in tank fuel pump, the fuel inlet is basically at the bottom of the tank (.250"-.375" off of the bottom
usually), so the full height of the fuel column (fuel above the pump inlet) is working to feed the pump on top of the low pressure
area the pump creates giving superior fuel feed to nearly any external fuel pump system.

5.) Value. Cost is something thats relative to each person, I could have bought a high dollar big name pump setup, but I graduated
highschool at basically the height of the 2008 depression, my frugal parents and life experience has taught me to value money.
Dropping the level of cash on the big name systems just didn't sit well with me for what my needs were and their performance
value. We'll discuss the cost of the lift pump/fuel system setup with each component, but the basic setup could be easily
replicated for about $200-$250.

6.) power, pressure, and flow. stock/mildly modified p7100 pumps have shown to pickup power to about 40-50psi of delivered fuel
pressure. as tested by PDD, fass' "fuel polishing" valve cracks as a overpressure relief around 40psi (the pump is also not
delivering anywhere near the advertised number at that pressure either). The pump I selected delivers the advertised flow at
pressure and has an internal pressure relief valve that opens all the way up 150psi (not that the pump flows much there, but hey
better to have it and not use it right?).

7.) clean installation. no wires or hoses or pumps hanging all over the frame. I found my install to be a very clean/sanitary finished
product and look very OE including using the factory electric fuel pump circuit already built into the truck and harness

That's all I've got for benefits over a "conventional" aftermarket lift pump system...

Basic component list (just to get it going, i'll list the extras later):

Pump: AEM 50-1005, retail on amazon: $151 (https://www.amazon.com/AEM-50-1005-I...QG4H51SJ5561JD). Read the info on it here (pressure/flow data, amp draw data, etc...) https://www.aemelectronics.com/produ...flow-fuel-pump

inlet filter: AEM 50-200-11, retail on amazon $12.20 (https://www.amazon.com/AEM-50-200-11.../dp/B00VBH912E)

8an to 3/8" hose barb: Derale 98201, $4 (https://www.summitracing.com/parts/der-98201)

Tile Drain coupler (you'll see where this comes in later): $2 https://www.menards.com/main/plumbin...33045&&ipos=33

Misc screws, hose, and clamps $20-free99 depending on what you already have and your resources.

So first thing you need to do obviously is remove the tank and sending unit. I despise the factory nylon tubing they started using in the early 90s on everything for fuel line, you can keep it but I personally always remove it and replace it with high pressure rubber hose and clamps. easy way to remove it from fittings/tubing is cut it length wise along fitting/tubing. releases the tension and easily comes off. You do need to save the quick connect fittings on the tank however if you are going to keep the install as clean as possible.

heres cutting the nylon lines
Click the image to open in full size.

once you have the fuel sending unit out you can start disassembling it. first thing should be the three screws holding the top to the bottom half, go ahead and cut the fuel line that goes to the center pickup tube and disconnect the two spade connectors on the fuel level sensor !!BE EXTREMELY GENTLE WITH THE LEVEL SENSOR, I WAS NOT AND NOW HAVE TO TAKE THE TANK BACK OUT OF THE TRUCK TO FIX IT!!! the other two hoses going down into and along side the sending unit should just slide out with the top of the sending unit, leave these attached.

here's a picture of the level sensor and two wires
Click the image to open in full size.

set the top of the sending unit aside for now, remove the level sensor from the side of the lower half of the sending unit (two screws) and set aside, remove pickup tube retainer, pickup tube, fuel return screen, fuel feed screen and fuel feed check valve/float (just pulls out from the bottom)

pickup tube retainer
Click the image to open in full size.

pickup tube

you should have an empty lower half of the sending unit. here are some pictures with the measurement of the inlet size of the sending unit feed and the ID of the inlet screen for the AEM pump.
Click the image to open in full size.Click the image to open in full size.Click the image to open in full size.

here are some pictures of the pump i'm using
Click the image to open in full size.

now is the point of no return, use a step bit to open up the bottom hole in the sending unit to just fit the nut for the pickup screen through, but not hex nut on the bottom of the pump body.
Click the image to open in full size.

I oriented the pickup screen so the long side was facing towards the right side of the truck, so in slosh around left hand turns it would remain more covered, if you want to orientate the pickup screen a different way that's fine, its your truck. cut clearances in the bottom of sending unit "feet" to clear the pickup screen. A fresh razor blade cuts through the plastic material pretty easily.
Click the image to open in full size.

Now, I would assemble the check valve and 8an to 3/8 barb onto the pump now rather than i did later, makes it much easier to tighten everything down than trying to fish a wrench down into the sending unit to snug everything up, you can hold the pickup screen by hand and thread the pump onto the pickup screen. you dont need to tight the pickup screen now, just snug it down to test fit it into the lower section of the sending unit. The pickup screen seals with an Oring, so it doesnt need to be much tighter than hand tight. You should have something similar to this (with the check valve 8an-3/8barb fittings on top). I recommend using some masking tap over the pickup screen and pump outlet to stop getting dirt and other schmoo into the pump/screen/lines.
Click the image to open in full size.

you'll see that the pickup screen will be drawn up into the pump body a bit, thats perfectly normal and good, you dont want the screen smashed against the bottom of the tank, about 3/8" of clearance from the bottom of the screen fitting to the floor of the tank is really what you want.

now you can test fit the pickup tube retainer over top of the pump. I oriented the pump so one of the body crimps that holds the pump together indexed with the hole for the fuel return tube, helps hold everything in place.
Click the image to open in full size.

Get the retainer figured out where you want it and take it back out (or dont, i dont care). now its time for the tile drain coupler. I was trying to figure out how i could increase the baffling around the pump pickup. the bottom half of the sending unit acts as a surge tank/reservoir for the pickup (and now pump), but i wanted a little extra around the pickup screen. looking around for some suitable material i was thinking of cutting up a fuel can and using parts of it, the plastic wont damage the inside of the tank like a metal baffle would and wont fall apart like fuel cell foam. i didnt really like the idea of cutting up one of my good fuel cans, so i looked at what material they were made of, high density polyethylene. Did a little more googling for HDPE and found that tile drain tubing and components are made from HDPE, so i went to my local store and looked around for HDPE molded on the side. not all couplers have HDPE on them, some have a ASTM standard number (F667) like mine, but ASTM F667 standard for polyethylene, so its all good.

Click the image to open in full size.Click the image to open in full size.
__________________
1997 xclb2wdotf, dying 47re, fuel plate MIA, 3kgs, 4" diamond eye, bhaf, kdp tabbed, fuel heater removed.

Last edited by gear_grinder; 06-18-2019 at 11:09 AM.
 
Old 06-18-2019, 11:05 AM   #2
gear_grinder
 
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the coupler should just fit around the bottom half of fuel sending unit, i cut a few notches for fuel to get through from the outside easier and a opening for the long side of the fuel pickup screen. I have it so its basically level with the feet of the factory sending unit. I secured it with some self drilling hex head screws, they easily drill through the polyethylene and cut their own threads (as youll see alot of the factory components are secured with screws that are just threaded into the plastic body). Test fit the top of the sending unit to make sure the screws and coupler do not interfere with the fuel level sensor or top half of the sending unit.

Click the image to open in full size.Click the image to open in full size.
Click the image to open in full size.Click the image to open in full size.

Now that you have the coupler baffle where you want it you can tighten the pump down onto the screen permanently. I would also get some wire (14ga is okay, 12ga preferably) and wire the ring terminals and attach them to the pump. you can tighten the ring terminals off against the blocks (not sure what to call them) that surround and the terminal, the thinner ring terminal will conform to the shape as you tighten it down to the studs on the pump. leave yourself plenty of wire (12" should be plenty) on each lead so you can route them around the other tubing and parts of the sending unit as you like. reinstall the top pump retainer and secure with some more self drilling screws checking before so they do not interfere with the top half of the sending unit (meaning the sheetmetal sliding section).

Click the image to open in full size.

Now, because the top retainer is moved up higher you will need to cut the fuel bucket return tubing off above the beaded area of the fuel return hose so it can slide down into the lower section of the fuel bucket/sending unit. Verify that what you're about to cut is the return tubing

Click the image to open in full size.

This 96 and my 97 trucks both have full circuits for electric fuel pumps built into them already and fused for 20amps. Why not use it? the connector in the sending units that is connected on the underside of the top of the sending unit should have open spaces for terminals for pump power and ground. Verify your truck has the fuel pump circuit before you go any farther. The terminals you need to use the factory connectors are called "delphi apex" terminals. I couldn't find any locally so i had to order some. you need two female 16-14ga size, you may have to buy a pack of more to get them. You may have a 6pin (96 and earlier) or 4pin (97 and later) connector depending on the year. The terminal pictures are from the harness side plugging into the sending unit, so verify connector orientation on the inside of the sending unit. test fit the top of the sending unit for wire length, always leave yourself a little extra. you should beable to tell how deep the sending unit sits in the tank by the witness marks left by the retaining screws on the sheet metal slider portion of the sending unit.

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.

you will need a pick or dentist tool to pull the internal portion of the connector forward enough to release the locking tabs for the terminals on the connector, with your apex terminals crimped onto your wire you can side them in and they should click into place then push the center lock back down to secure them

Click the image to open in full size.
Click the image to open in full size.

now you can cut the remaining nylon feed tubing off of the top of the sending unit, i found it easiest to remove the sheet metal sliding bracket to remove the line and clean everything up (my sending unit was a little skuzzy for my liking). I simply replaced this with some 3/8" transmission cooler line and "EFI style" band type hose clamps (dont use the worm gear clamps if you can help it, they tear up the hose). I have used transmission cooler hose for over 10 years in high pressure fuel applications without an issue. reinstall the sheet metal slider and test fit for hose length like you did the pump/sending unit terminals (leaving a little extra is fine, just not so much that it will kink when at installed height in the tank). doing to the clamps up is a little finiky as they are obstructed by some of the sending unit, but it can be done with a long screwdriver. connect the pump/level sensor connector and clamp down the feed hose, thread the return and vent hose back down through the sending unit and refasten the sliding section to the bottom half of the pump. Congratulations! your in-tank pump conversion is ALMOST finished lol. the in-tank section of this is anyway... your sending unit should look like this.

Click the image to open in full size.Click the image to open in full size.Click the image to open in full size.

reinstall unit into the fuel tank

Click the image to open in full size.

Now, all you need to do is power it up and adjust fuel pressure. Im not sure where the factory overflow valve will regulate pressure to because i already had an adjustable unit on mine. with the adjustable overflow valve basically all the way backed off i get 40psi key on engine off and a little over 40psi running at 14.5v.

The entire circuit is on the truck, however the ECM never pulls the relay for the circuit to ground. All you need to do is provide a ground for the coil of the relay (coil power is switched by the key). You can figure out what circuit is the switched coil power with a multi meter and the terminal opposite of that is the grounded circuit (should have no power key on or off and no continuity to gound). I loosened the fuse box off of the fender and cut the wire off of the harness with enough length to solder on a length of wire to run a ring terminal out to the fender to an existing ground near the fuse box (sorry i forgot to take pictures of this)
Click the image to open in full size.Click the image to open in full size.

Now here's where the extras come in. You could do this with stock fuel filter and just bypass the pump (cutting off and putting a small bead on the fuel feed line that would come from the pump and clamp a section of transcooler line on from the factory hardlines on the engine/frame. I removed my entire factory filter/pump assembly and put a larger 10micron fuel water seperator and a 2 micron fleetgaurd filter on a bracket i made to use existing frame holes. if you want more detail about this, ill reply to this thread about it. here are some pictures

Click the image to open in full size.Click the image to open in full size.Click the image to open in full size.Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.

https://www.youtube.com/watch?v=sQbIDryh9Wg
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1997 xclb2wdotf, dying 47re, fuel plate MIA, 3kgs, 4" diamond eye, bhaf, kdp tabbed, fuel heater removed.
 
Old 06-19-2019, 07:16 AM   #3
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Interesting.
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