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Got the dual 1/2” lines run from the sump to the pre-filter.
It’s tight running twin 1/2” lines up between the frame and the tank. Crappy picture, bad lighting.
Better lighting.
The relay/fuse box showed up today. I wasn’t expecting it to be this big. Looks to be the size of 1/2 a red brick.
Line break between pictures to appease the grumpy old man from Oklahoma.
Gotta figure out where I’m going to mount this beast.
It will be mounted just below the master cylinder off the under hood fuse box bracket.
Trigger wires and fuel pump feeds will be routed out the back. Power in and ground will run out the front.
The blue wires are for future use if ever needed and are all fused as well. I’m going to pull those fuses from the box so they are just dead wires and loom them up and out of the way.
One sump dual outlet, dual pumps, dual lines. Single feed into the engine.
Anyone see a problem here? When does one of the dual feed lines becomes a return line?
One sump dual outlet, dual pumps, dual lines. Single feed into the engine.
Anyone see a problem here? When does one of the dual feed lines becomes a return line?
For now I’m retaining the factory fuel pressure regulator and return line.
If I find that the feed is overwhelming the factory setup then I’ll have to do it differently for the regulator and return.
Wiring is completed besides the connections to the fuel pumps. Was waiting all day on the wire boots to show up. Of course 10 minutes after I packed it in and cleaned up they arrived.
Grounded to the firewall. Wire loom routed and zip tied. Nice and clean. Just the grounds and +12v to finish this off. Lookee what I got. These fit like a glove onto the fuel pump. The wire side of the boot is stepped so I will need to trim it to accommodate the 12ga. Doesn’t look like there’s enough girth to use a heat shrink on the eyes.
As you have setup you system, everything should flow in a forward direction towards the engine. What happens when a pump takes a dump? I know these pumps are super reliable, but what happens to the fuel flow direction? Consider the fuel regulator as a restriction to over come and now you have a dead pump. How does the single pump filtration flow/pressurize the lines?
Last edited by Hyperpasta; Jan 5, 2026 at 09:57 PM.
As you have setup you system, everything should flow in a forward direction towards the engine. What happens when a pump takes a dump? I know these pumps are super reliable, but what happens to the fuel flow direction? Consider the fuel regulator as a restriction to over come and now you have a dead pump. How does the single pump filtration flow/pressurize the lines?
Beauty thing about these Bosch pumps is there is a built in check valve so the system doesn’t bleed down. If one pump goes down I’ll see the pressure drop under load but it should still have enough pressure for drivability.
I will test the system with both pumps running simultaneously, then cut power to each pump independently to confirm my theory.
There is a very long story previous to going down this current rabbit hole. I won’t get into all of it now. Go back in this thread and read the back story.
I installed the Riff Raff black spring and initially had 68Lbs fuel pressure but saw that drop over time to about 62. Under heavy load it’s dropping 7-10 lbs. Yes brand new filters, yes confirmed with a mechanical gauge.
Saw a picture on the internet. I got a spare pump in my tool box so… what the heck. Rabbit hole here I come.
Is it going to work flawlessly, I dunno.
Is it going to overwhelm my return line system, I dunno.
Am I going to find out, you betcha I am,
and I will figure out how to deal with it if there is an issue.
Edit: And if I do have an issue with the system as currently designed and installed it will be documented here along with the remedy for all future readers.
Last edited by F350towing; Jan 6, 2026 at 12:20 AM.
So, I've got a question here. You're doing 2 pumps not because you need the volume, but for redundancy?
With a check valve in ea pump, if one dies, how would you know? Do you have an indicator that I missed?
If one does die you'll keep driving until the other dies and still be left on the side of the road w/o some kind of indication that the first pump has failed.
It might almost be better if they didn't have a check valve and instead had manual valves. So if one fails the truck stops and you're forced to isolate the bad pump via a manual valve - so you then know and can take preemptive action.
So, I've got a question here. You're doing 2 pumps not because you need the volume, but for redundancy?
It is actually for increased volume. My hope is that it will hold pressure under heavy load and I won’t see the drop of 7-10 Lbs.
With a check valve in ea pump, if one dies, how would you know? Do you have an indicator that I missed?
With the single pump it was dropping pressure under load. Hoping that with the current setup if a pump goes down I will see it on my fuel pressure gauge.
If one does die you'll keep driving until the other dies and still be left on the side of the road w/o some kind of indication that the first pump has failed.
Pressure drop under load will be my indicator.
It might almost be better if they didn't have a check valve and instead had manual valves. So if one fails the truck stops and you're forced to isolate the bad pump via a manual valve - so you then know and can take preemptive action.
Check valve is integral with the factory fuel pump so no way to get around that.
Beauty thing about these Bosch pumps is there is a built in check valve so the system doesn’t bleed down. If one pump goes down I’ll see the pressure drop under load but it should still have enough pressure for drivability.
I will test the system with both pumps running simultaneously, then cut power to each pump independently to confirm my theory.
There is a very long story previous to going down this current rabbit hole. I won’t get into all of it now. Go back in this thread and read the back story.
I installed the Riff Raff black spring and initially had 68Lbs fuel pressure but saw that drop over time to about 62. Under heavy load it’s dropping 7-10 lbs. Yes brand new filters, yes confirmed with a mechanical gauge.
Saw a picture on the internet. I got a spare pump in my tool box so… what the heck. Rabbit hole here I come.
Is it going to work flawlessly, I dunno.
Is it going to overwhelm my return line system, I dunno.
Am I going to find out, you betcha I am,
and I will figure out how to deal with it if there is an issue.
Edit: And if I do have an issue with the system as currently designed and installed it will be documented here along with the remedy for all future readers.
That's great!
I had no idea the the OEM pumps had a check valve built into them, your golden then.
Well done!
The RR FPx and HPx kits are solid for tightening up fuel delivery and sealing weak points, but you’ll get the most bang for your buck by fixing the plenum leak first and then moving to the hutch and harpoon upgrades. Once those are in place, a good scan tool from (Moderator Note: Commercial Advertising Link Positioned here is removed, while AI sourced text content is left extant so that readers can understand the context of F350Towing's response) can help you verify that boost, EGT and fuel pressure stay within spec after each change. Keep an eye on fuel pressure stability and any lingering MAP leaks—they’re often the hidden culprits that bite you later.
SixToV8, (Moderator's Note: SixToV8 is now banned, and all prior posts have been deleted)
Your quite late to the party.
FRX, Fuel delivery lines from bowl to heads Hutch and Harpoon, and Plenum Reseal with Riff Raff inserts were all done somewhere around 4 years ago. I'm using FORscan to monitor and scan for codes when required.
Fuel Pressure, Boost, EGT, TFT, ECT, Oil pressure and Rear diff temps are all monitored off of wired gauges. It's all in my signature.
Appreciate the info though, and welcome to FTE.
Edit: and it appears that a see-ya is also in order. Damn Ai. I thought that post was weird but I didn’t want to be rude.
Last edited by F350towing; Jan 8, 2026 at 11:47 PM.
