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Discussion Starter #1
Let me begin by stating that my fuel system has been bastardized. The mechanical fuel pump and fuel bowl are gone. I run a frame mounted Bosch fuel pump with a particle filter and a fuel/water separator.

Last night, the truck stalled out. After some digging, it turned out to be losing fuel pressure while running. Cycle the ignition to cycle the pump & the truck would start and run again. I changed the fuel pump and both filters... issue remains. Truck loses fuel pressure while running.

My mechanic buddy thinks it's an injector... any other possibilities?
 

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How much fuel do you have in your tanks, if you are at around 1/4 of a tank you could have broken pick ups (Shower Heads) and not getting the last 1/4 to 1/3 of your tank(s). After replacing both my tanks and seeing my shower heads floating around in the bottom of my old tanks it is a wonder I did not run out of fuel several times. Just my first guess
 

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Both of mine were gone, but I couldn't see the pieces in the front tank because it's black plastic, & ~2x as deep.

Just ignore all the dirt in the tank - it's the maid's day off.

159072


I bought the cheap imported replacement kits, which seem to be OK.

159073


IDK what the 2 smaller cylindrical filters are for.
 

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Discussion Starter #4
That's definitely worth checking into. Truck has 300k+ miles and no telling if that's ever been changed.

Yesterday morning I primed the fuel system before I left for work. After sitting all day, it only lost 20psi... while running, it drops fast enough to watch the needle drop.
 

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This is only relative to your situation if the truck is down to around 1/3 to 1/4 in the tank you are running on. Simple test would be to fill that tank and run just on it and see what happens. At 300k I bet the feet are floating around in your tank, both mine were at 226K on one truck and i bet my 302k truck is the same. That is the reason I never try to run lower than 1/4 in any tank
 

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Discussion Starter #6
Both tanks are full and same problem. Now that the rain has let up here, I'm going to bypass the tanks and run from an external tank... that will at least point me to the correct half of the truck. I'll also be verifying that the fuel pump is getting the full 12vdc it's supposed to.
 

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Discussion Starter #7
Figured out the what, now I have to figure out the why... fuel pump is only getting power key on, engine off. On start, pump looses power. Simple enough to bypass the module for now.
 

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Some Dodges have fuel lift pumps that only run when starting, and then stop running until the next start-up. I guess they just need the pressure boost when starting, after which the engine's fuel pump takes over.

Maybe your pump has such a controller on it?

If so, just wire 12VDC directly to the pump on a key-on fuse circuit.
 

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Discussion Starter #9
Some Dodges have fuel lift pumps that only run when starting, and then stop running until the next start-up. I guess they just need the pressure boost when starting, after which the engine's fuel pump takes over.

Maybe your pump has such a controller on it?

If so, just wire 12VDC directly to the pump on a key-on fuse circuit.
I've got an efuel kit that primes the fuel lines for about a minute and then cuts off... after the truck is started, it turns the pump back on... or it use to. I'm back tracing the wiring to see how it knows the engine is running. It ties into what appears to be a red/green wire where the fuel bowl use to be.
 

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Discussion Starter #10
Got it sorted... my efuel kit runs off an oil pressure switch to determine if the engine is running... and, one of the wires was broken. My F350 is back in service! I love the cheap easy fixes.
 
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