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Discussion Starter · #1 ·
had some poor mileage problem

DS4 IP seem to works but...
when check out with Tech 1:
no DTC
TDCO learned -1.5 (fine) ...relearn at same value
DES/ACT timing 4.9 (very low timing value vs TDC )
fuel mm 12 (too high at idle).

about 230.000 km on it.

think is an IP problem but ask to some Guru if is time to change IP or there is something to check before buy a new one.
 

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had some poor mileage problem

DS4 IP seem to works but...
when check out with Tech 1:
no DTC
TDCO learned -1.5 (fine) ...relearn at same value
DES/ACT timing 4.9 (very low timing value vs TDC )
fuel mm 12 (too high at idle).

about 230.000 km on it.

think is an IP problem but ask to some Guru if is time to change IP or there is something to check before buy a new one.
Is the engine up to operating temps when you get those values?
 

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Discussion Starter · #3 ·
yes, about 183 F over the mimimun temperature request for TDCO procedure
 

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Is it throwing any codes?
 

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Discussion Starter · #5 ·
no current and history DTC
 

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If your injectors are the old original equipment. They are way past their service life. I would check/replace injectors before doing the pump. Bad injectors will drop your fuel mileage.
 
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Discussion Starter · #7 ·
new injectors.... about 20.000 km ago
 

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A stretched/worn timing chain can cause issues
 

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Discussion Starter · #9 ·
"A stretched/worn timing chain can cause issues"
True... but i think if the timing chain is stretched/worn, you can see also difference from DES and ACT timing. if the value is very close and no degree delta average between the 2, i will suppose timing chain is OK, or i am thinking bad?
 

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Discussion Starter · #10 ·
the question is what can cause a so low timing advance with a TDCO set to -1.50?
usually i seen 8-8.5 DES/ACT timing with TDCO set at -1.50
and a value of 4.9 i have now is out of spec, or what i had before
maybe a bad stepper motor ? (but i have not a code 34 or other code related)
bad OPT sensor?
or something else?
the only issue happen before was a shorted cable to ground to IP Shutoff Solenoid that cause engine shutoff (isolated/repaired the cable it returned to works).
 

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Discussion Starter · #11 ·
it was long time never check with Tech 1A the timing....
and a Fass lift pump set to 14 psi was installed, ... more then needed to IP? ...too much pressure can take effect on timing?
when installed Fass LP seen what pressure is raccomented, and 14 psi was in spec, or not so bad for a DS4 IP...seen others forumist setting more pressure, but i don't know if their IP timing changed.
for what i know DS4 is not influenced by inlet pressure...or not?
 

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it was long time never check with Tech 1A the timing....
and a Fass lift pump set to 14 psi was installed, ... more then needed to IP? ...too much pressure can take effect on timing?
when installed Fass LP seen what pressure is raccomented, and 14 psi was in spec, or not so bad for a DS4 IP...seen others forumist setting more pressure, but i don't know if their IP timing changed.
for what i know DS4 is not influenced by inlet pressure...or not?
My airdog runs at 11psi. The DS4 only needs 5psi constant to be happy.

I would reduce your pressure down to 11-12psi.

Anything above and beyond that will get returned to the tank via the return so you basically end up just polishing your fuel constantly
 
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My airdog runs at 11psi. The DS4 only needs 5psi constant to be happy.

I would reduce your pressure down to 11-12psi.

Anything above and beyond that will get returned to the tank via the return so you basically end up just polishing your fuel constantly
What scanner or software are you using to see that info?
I need to test it too
 

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Discussion Starter · #14 ·
What scanner or software are you using to see that info?
I need to test it too
economic way:
you need a pressure gauge for it
you can measure at T valve from fuel filter, if the tap is in good condition and does not leak from the orings when opened
otherwise you have a false measurement (something less...depend from leaks).

more expensive way:
for a more precise and constant measurement you could buy an electronic pressure gauge with the pressure sensor positioned on the fuel hose that goes from the fuel filter to the IP, and gauge inside the cab.

that's all
 
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What scanner or software are you using to see that info?
I need to test it too
I have Fuel pressure, Boost and EGT gauges in my truck to monitor things
 
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