2008 6.4 loosing rail pressure

JBird08 · Aug 6, 2019

Mods:
100% nozzles added to previously replaced 10k mile motorcraft injectors
dual fuelers(Elite kit), both have been replaced in attempt to repair
Return fuel system, elite, regulated to 9.5 psi, monitored and sustained
s476 kit, H&S

Under heavy throttle, injection pressure falls off and vehicle looses power. Fuel pressure maintains and vehicle drives normal under all other circumstances. Any thoughts?

Black AOD · Aug 6, 2019

Good luck with this, I fought this issue on my old 6.4 for a while. How old are your k16s injection pumps? How many miles? K16's were not the greatest pumps ever and were notorious for bad PCV's and the internals wearing quickly due to fuel contamination

JBird08 · Aug 6, 2019

Black AOD said:
Good luck with this, I fought this issue on my old 6.4 for a while. How old are your k16s injection pumps? How many miles? K16's were not the greatest pumps ever and were notorious for bad PCV's and the internals wearing quickly due to fuel contamination

When the problem showed itself, I replaced both pumps with motorcraft rebuilds, same issue instantly

Black AOD · Aug 6, 2019

JBird08 said:
When the problem showed itself, I replaced both pumps with motorcraft rebuilds, same issue instantly

Motorcraft rebuilds are known for being junk as well.

I would have the pumps and injectors flow tested. If it still occurs, it may be the low pressure system. If it's not that, it may be your PCM failing. That's what mine ended up being although mine was an oddball case.

JBird08 · Aug 7, 2019

Black AOD said:
Motorcraft rebuilds are known for being junk as well.

I would have the pumps and injectors flow tested. If it still occurs, it may be the low pressure system. If it's not that, it may be your PCM failing. That's what mine ended up being although mine was an oddball case.

What was your symptoms?

Black AOD · Aug 7, 2019

JBird08 said:
What was your symptoms?

Twin pumps and 100% overs with mid sized VGT compounds and no matter what we did it would drop rail in all gears and had serious power loss. We went through my fuel system top to bottom, three times. Replaced every part possible.

Finally on a random whim we tried a new PCM. Fixed everything

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