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I have a 871 that has been mm'd. The last week it has been acting like it is starving for fuel sometimes when leaving a stop or after coasting for a few minutes. I hooked up insite and ran it on monitor for about 4hrs. When it would act up it was showing air fuel control create. I was playing with different things and if it got over 1800 in the low side it would show noise derate.
Idle fuel pressure is 260
Cruising is 268-272
Pulling a hill 270-276 generally
In 4 hrs the lowest it went was 255 highest was 279

I initially thought it was bad filters so I changed them when problem started. No change then looked for it sucking air. Changed primary filter housing but problem still exists.

I'm kinda thinking it's either regulators or gear pump but not sure.
Those fuel pressure numbers appear to be in the "nominal" range, and I don't believe it's pump related.

Have you performed injector leak test Procedure 006-026?
Yes sir. Did one on Monday. No bubbles. I was thinking it was supposed to be around 275 idle
As per Quickserve:
100psi at 130rpm while cranking for 10 seconds (no start condition check)
230-270psi at low idle 600rpm
275-325psi at high idle 1800rpm

Insite will tell you the pressure of the fuel rail while connected. Remember, the proper way to test is a mechanical guage connected to the compucheck fitting, but insite is a valuable tool if you don't have a mechanical gauge available.

[attachment=2817]

Post #20 in this tread has my results, which IIRC are the same as mine were during my road testing.
http://rawze.com/forums/showthread.php?tid=1365&page=4
(06-04-2017 )Rockycoon75 Wrote: [ -> ]Yes sir. Did one on Monday. No bubbles. I was thinking it was supposed to be around 275 idle

Reviewing my old thread, quickserve, and your posted pressures, they are fine. I don't believe it's the fuel pump. I think you are going to have to delve into the issue deeper and follow the troubleshooting tree. Perhaps a phone call to one of the gurus may point you in a more specific direction.

I have no experience or first hand knowledge to draw this from, but to me it almost sounds like it could be an actuator starting to occasionally hang up on the step that gets worn into the small shaft on them. This is just a guess and I'm completely full of it, but perhaps a starting point?

Where are you located?
What is your boost and pyro doing? That is where I would start, the simple things.
Good morning beautiful I love you When it derates the boost stays around 5-10 when it clears it will go to 33ish. When running correct it was running around 38. Pyrometer runs around 7 usually but now that this has started it's pushing 8. I went to Albuquerque last week and I had to back out of it because it got to 9 and still climbing.

It did this a couple of times in the past but only for a second. Now it's happening quite often.

Don't have mechanical guages. I don't think mine is going that high at 1800 but will check it again shortly
(06-04-2017 )Rockycoon75 Wrote: [ -> ]Good morning beautiful I love you When it derates the boost stays around 5-10 when it clears it will go to 33ish. When running correct it was running around 38. Pyrometer runs around 7 usually but now that this has started it's pushing 8. I went to Albuquerque last week and I had to back out of it because it got to 9 and still climbing.

It did this a couple of times in the past but only for a second. Now it's happening quite often.

Don't have mechanical guages. I don't think mine is going that high at 1800 but will check it again shortly

Could be turbo related, could be a air-air leak, could be imap sensor or other sensor starting to go bad. could be a lot of things.

BTW: It is quite normal to get a fuel derate message for a few moments in the engine state parameter during hard acceleration. This is because the engine is limiting fuel while the turbo catches up to itself and is for ensuring there is no black smoke. Once it catches back up to itself, it should change. For example, if the accelerator pedal is on the floor, it will change to "max throttle" after it catches up again.

What is NOT normal is low boost levels and excess hesitation. Sounds like the engine is having some kind of issue like stated above.
Imap new on the 17th. Air to air tested good.
Fuel pressure at 1800 is 276 so in range but on The bottom end The derate and low power will last all the way through the low side usually starts to pick up and go when i get to the high side.
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