Diesel Fuel system question (specifically 24v Cummins)

Tacoma747

Tacoma747

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Winston-Salem
I recently bought a 2005 f-350 that had a 24v cummins swapped into it, I have been addressing some issues with it and just finished building a fuel filter setup for it (to make use of a large quantity of Cummins brand filters I have on hand).

The filter bases use 12mm fittings, which turns out is the same size as the banjo bolt on the injector pump. I got to thinking about flow restriction after seeing the small ID of some of the fittings I was using (6 JIC), but the factory fuel line is 5/16", and a 5/16" Barb fitting is not that much larger than the 6 JIC, but regardless I ordered new fittings online to change everything to 5/16 Barb fittings (which will get rid of the 6 JIC adapters)

I see after doing some research about people upgrading to larger lines, even found a suggested banjo bolt that goes at the injector pump that has a .187 opening instead of a .130 opening. So for that matter it seems like a waste to upgrade fittings anywhere else if the injector pump fitting is the smallest diameter fitting. Am I over thinking this?

The truck has some sort of in tank fuel pump, not sure what it is. I put a gauge on top of the 2nd filter (on the outlet) and it reads 10psi at idle, drops to about 8psi at WOT (no load). Not sure what the pressures are while driving. Finding mixed opinions online if that is too low or not.

Opinions?
 
Is it still a VP44 injection pump?

Also...a -6 fitting is 3/8" ID, which is larger than 5/16"....so, you kinda lost me there.

If it's a VP44, they're pretty picky about fuel pressure. I'd definitely find out how far the pressure drops under a load. If I remember reading it right, that truck has twins so that means it probably has bigger injectors and some demanding tuning that requires a good amount of fuel.
 
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Need a minimum of 10 at all times, so idle would be higher. If you have a larger fuel line from tank to injection pump it will allow more volume to be available on demand faster and a larger line is easier for the pump to push the fuel through.

Also a hard line is easier to push fluid through than a rubber line since theirs not as much friction on the inside wall of the line.
 
Well maybe it isn't 6 JIC now that I think of it. For some reason I thought the guy told me they were 12mm to 6 adapters. I guess for peace of mind I will probably go ahead and change everything to larger fittings. May upgrade to a higher flow frame mounted pump as well at some point.

It IS a VP44, but it is not a twin turbo. It is not super fast or anything so I feel it is probably stock, but I don't know.
 
I was thinking of @bashed but his is P-pumped. My bad!
 
Yeah the factory lift pump on the VP44 trucks isn't really up to the task of even a stock truck. The pump is fine when relatively new but when age goes up the pump ability to keep up with demand falls off, and when the injection pump doesn't have enough flow inside to lubricate and keep it cool it goes out soon after.
 
I usually run either the air-dog df100 or 165 w/vp44 depending on what I'm doing with the truck. I can maintain 10-13 psi under heavy throttle with load using the hoses provided w the kit and a sump. My superduty is running a df200 and maintains 30-32 psi under heavy load. It's got a 12mm Dragonfly running dual feed and approx. 75 hp injectors and twins. My biggest hurdle at the moment is keeping the hot side boot on while towing and trying to maintain 50+psi of boost.
 
Tacoma747 said:
I recently bought a 2005 f-350 that had a 24v cummins swapped into it, I have been addressing some issues with it and just finished building a fuel filter setup for it (to make use of a large quantity of Cummins brand filters I have on hand).

The filter bases use 12mm fittings, which turns out is the same size as the banjo bolt on the injector pump. I got to thinking about flow restriction after seeing the small ID of some of the fittings I was using (6 JIC), but the factory fuel line is 5/16", and a 5/16" Barb fitting is not that much larger than the 6 JIC, but regardless I ordered new fittings online to change everything to 5/16 Barb fittings (which will get rid of the 6 JIC adapters)

I see after doing some research about people upgrading to larger lines, even found a suggested banjo bolt that goes at the injector pump that has a .187 opening instead of a .130 opening. So for that matter it seems like a waste to upgrade fittings anywhere else if the injector pump fitting is the smallest diameter fitting. Am I over thinking this?

The truck has some sort of in tank fuel pump, not sure what it is. I put a gauge on top of the 2nd filter (on the outlet) and it reads 10psi at idle, drops to about 8psi at WOT (no load). Not sure what the pressures are while driving. Finding mixed opinions online if that is too low or not.

Opinions?
Click to expand...

I think you are over thinking it. 3/8 or -6 lines should be plenty. However, I'd want a little more pressure than 8 at WOT.
Check that in tank pump.

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@Chris_M I figured out they are not -6. They must be -4 or something, they are definitely not 3/8" ID. I just ordered a bunch of fittings and 500 feet of push-lok hose (the hose rang up as $1.66 but shipping was high for what I ordered at $33, so we will see what I get... When I tried to order 25 of the '500 ft' hose the shipping charges were astronomical (thousands). Maybe it slips through the cracks, maybe not, it was worth a shot!

I will be upgrading the fittings to -6, including removing the banjo on the injector pump and replacing it with a JIC. Once I do all that I will revisit the pump issue and possibly run 3/8" line all the way to the tank.
 
I need to do some research and see which filter should be first in line. The one I have 2nd in line (closer to the injector pump) is a lubricity additive filters and has a water separator on the bottom. I am thinking it might should be 1st but I am not sure. I guess my fuel system might have to be almost completely redesigned haha.
 

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I just googled the part numbers:
FS20022 this is a water separator/lubricity additive, not sure it is considered a 'filter', but they are $67 each!!

FF5421 is a 4 micron fuel filter.

I feel like I have seen systems before with a separator 2nd in line, and I also feel like the 'additive' would be better off AFTER the fuel filter to avoid any of it getting stuck in the filter. I guess I need to try to find out a definitive answer.
 
Fyi I bought the hose for my air dog 165 at monarch fastener in kernersville. It was cheaper than buying online with shipping added in.
 
Chris_M said:
Water separator definitely goes first. It is a 25 micron filter. Then the 4 micron goes next before hitting the injection pump.

Cummins Filtration - Catalog - Part Search
Click to expand...


Yea I started building this was only going to use one filter. Then decided to add the lube filter and didn't do any further research. Now I basically get to rebuilt the whole setup haha. I am going to go ahead and order a different lift pump just to go ahead and know what I have. I will wait until I run most of the fuel out of the tank before I drop the tank to figure out what is in it though.
 
Fuel Pressure Specification For Bosch VP44 Injection Pump
This is a good read I run 1/2" line and a air dog the intake pump you have is probably the factory recall fix it just moved the shitty block mounted lift pump to a equally shitty intank pump I keep my pressure at 15psi and it never drops below 12psi the factory relief valve is I think 14 or 15 psi but they make after market ones with higher pressure settings
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I'v got a buddy with a bone stock 02 VP44 truck and not the first gauge....I cringe when I think about that. He/his wife have run it out of fuel three times. I don't think they know how much they're pushing their luck!

bashed said:
My biggest hurdle at the moment is keeping the hot side boot on while towing and trying to maintain 50+psi of boost.
Click to expand...

Do the pipes not have a bead rolled in the ends of them? I know twins drive harder down low, but I can shove 56 lbs in my first gen and the intercooler boots never flinch. I do have 3" charge pipes and some nice 5 ply silicone boots though.
 
Croatan_Kid said:
Do the pipes not have a bead rolled in the ends of them? I know twins drive harder down low, but I can shove 56 lbs in my first gen and the intercooler boots never flinch. I do have 3" charge pipes and some nice 5 ply silicone boots though.
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It does. It's also 3" as well, found a 5 ply on StainlessDiesel.com that I'm gonna order this week. Hopefully it'll get the job done.
 
bashed said:
It does. It's also 3" as well, found a 5 ply on StainlessDiesel.com that I'm gonna order this week. Hopefully it'll get the job done.
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Spray Hairspray on the flange then slide the boot on. That will help with holding it on as well.
 
Decided to go ahead and just mount the airdog 150 fuel system on the truck. I'll use the huge supply of fuel filters on something else.

I dropped the tank on the truck today to mount a fuel sump in the bottom, I cut the wires going to the in tank pump, whoever put the pump in spliced the wires (the hot and ground) 4 times on EACH wire. That was just between the factory connector and the fuel tank (beside front driveshaft).

Ridiculous the corners some people cut with wiring.
 
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