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The thought of buying a new fuel bowl has crossed my mind. That is a good observation l. I have never had thisb part before. Its pivotal to the truck running and this one is rough and old. Maybe the spring was never there and the line was smashed up to the regulator bits and made enough pressure? I wouldn't be surprised if its cracked or something.
Im going to look around the garage for a rouge spring or strange metal bit.
Something that has just occurred to me is that it may have purposefully been gutted if the P.O. had installed an aftermarket fuel pressure regulator somewhere down the line.
What was your deadhead pressure at the fuel pump?
Looking closer at the FPR Housing you showed... that thing has been gutted for a long time.
Any chance you can take a video of underside drivers side of truck where fuel lines run, and under hood as well engine valley/ fuel bowl. Will have to upload it to youtube then post the link here.
Last edited by F350towing; Dec 30, 2025 at 06:32 PM.
Reason: added observations and thoughts
Something that has just occurred to me is that it may have purposefully been gutted if the P.O. had installed an aftermarket fuel pressure regulator somewhere down the line.
What was your deadhead pressure at the fuel pump?
Eff me.
So the truck came with a beast of a fuel pump. It was leaking so i swapped it not even thinking about that. It has a fuel pressure gauge on it. Maybe it was gutted for this, but i removed this pump 5 years ago....
The gauge is obviously in 100% great shape. I ordered new seals for this pump and rebuilt it, but it seems kinda ridiculous for a diesel pump so i never reinstalled it. It would rock vege oil.
If that pump was the FPR then when you pulled it 5 years ago the fuel pressure would have shat the bed back then.
And 50 000 miles later, i distrub the return lines and all h*ll breaks lose. I bet that fuel line sitting on the back of the guts was allowing just enough restriction to run the truck. I wonder if it would have ran if i pushed that line harder in to the assembly before tightening or something?
I have ordered a fuel pressure gauge so i can monitor this going forward in real time.
Seriously though. No major issues in 5 years. It no pavement princess either. Tows the rv. We use it for everything its worth. Coil swapped it 1.5 years ago. Had a map sensor pipe pop an that really slowed things with the rv in the mountains one time. I knew the system was heavily modified and knew what i was getting into. That said i have learned something today.
It also could have fallen out last week when i took the bowl out. I didnt notice anything but who knows.
Edit: i havent touched the fuel bowl until last week since owning the vehicle other than filter changes.
Last edited by Hellraiser456; Dec 30, 2025 at 07:36 PM.
Let’s see what happens when the new Dorman FPR goes in tomorrow.
Did you deadhead test the current fuel pump?
Have you checked Voltage at the fuel pump?
I disconnected the batteries as i was messing with the aih relay to get the fuel bowl out. Since the drain was leaking (and now non functioning appearently) i decided to start there. Ill dead head test from the supply line at the bowl once the frp arrives and i can head to the truck. Test voltage too. I didnt cycle the pump yesterday. I got one good start left in the batteries before i gotta pull them out to charge them.
Given what i found, a solid baseline will be important to enusre the system is working properly. The dead head test will be good to determine my contraption of a fuel system is working on the supply side.
With the gpcm, how do i temporarily disable it? Can i pull a fuse? Just unplug it? No use burning power for fuel pressure tests.
Dead head pressure at the fuel line to the bowl. Looks good. Took about 2 to 3 seconds to go up. This is from the aftermarket tank. This would be the first pressurization since ot being apart.
Pump has just under battery voltage and gound ohms out at around 1 ohm to the frame right by the pump. Batteries are low.
A guy should charge them, but we shall see if it will start with what its got.
Im going to put the new regulator in and measure bowl pressure when i get there. So far so good.
Its alive. Fired right up. Sounds a bit cackly but i think there will be lots of air to work out.
Problem though. Fuel pressure is 95psi. The reviews on the jungle site said this can happen. The kit came with a blue spring. Can i cut the spring a bit and accept i need a new bowl. Ill probably need to import one, so it will be some time.
fuel pressure only built to about 20 psi before i started it. Shot right up to 95 once i hit the starter.
I hear this kind of pressure can hurt the injectors. Will it?
Can i drive it home about 15 miles like this?
After a few minutes in writing this post, pressure fell to just above 30psi (edit, with the ignition off).
Thoughts?
Last edited by Hellraiser456; Dec 31, 2025 at 06:39 PM.
I didnt have a chance to look. Given the amount of cranking, and about an hour or so of on time flat towing and messing around, a lower voltage is expected. It was only a few points off, and this was during the deadhead test, which would draw more current than typical i would imagine.
My opinion, 45 psi is borderline to start causing issues. I don't know of an absolute psi number as there are a ton of variables. But the idea to maintain fuel pressure is not just lubrication of the internals but also pressure to push the Plunger back up after it has done it's injection of the fuel, for best injector performance. 7.3's just like to be around 60 - 65 psi of fuel pressure. If you try 85 psi or more you lose performance, and if you run 45 - 50 psi you lose performance. I made these changes on a dyno probably 18 years ago and this is what I found. But try for 60 - 65 psi so IF your pressure drops 5 or 10 psi then you're still safe from harm. Performance might suffer, but you'd still be safe from damaging the injectors. If you see 45 psi at idle and then it drops to 30 psi or less under load, then you certainly will cause injector damage.
I’m not sure what you have going on there and without having the truck in my shop doing the checks to eliminate I’m just throwing darts.
With all that aftermarket stuff in there it just makes it more difficult to diagnose.
Is the FPR leaking between the bowl and the housing? Maybe those almost stripped threads have let go and it’s losing pressure there. How about the newly replaced fuel drain valve?
Seems like either the pump isn’t building or something is bleeding off the pressure.
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