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Loss of rail pressure under heavy accel

Old Aug 14, 2019 | 09:23 PM
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Loss of rail pressure under heavy accel

I need some advice . I have an 03 with 60hp injectors a stock CP3 and a smarty set at level five. Under heavy acceleration from a stop the truck takes off fine. Shifts into second gear and rail pressure drops to about 8300psi. The truck bogs down terribly. This lasts for about 2seconds before the rail pressure returns to normal and the truck takes off like it should. I checked the FCA and it checks out fine. I’m not sure where to look from here. Any suggestions would be greatly appreciated. Thanks in advance.
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Old Aug 21, 2019 | 05:05 PM
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From: Calgary, Alberta, Canada
Originally Posted by Creekflea
I need some advice . I have an 03 with 60hp injectors a stock CP3 and a smarty set at level five. Under heavy acceleration from a stop the truck takes off fine. Shifts into second gear and rail pressure drops to about 8300psi. The truck bogs down terribly. This lasts for about 2seconds before the rail pressure returns to normal and the truck takes off like it should. I checked the FCA and it checks out fine. I’m not sure where to look from here. Any suggestions would be greatly appreciated. Thanks in advance.

1st up is to check your low side (lift pump) fuel pressure with an in cab gauge.

I hope you have an EGT gauge if your turbo is still stock. Smarty set to level 5 with 60hp injectors will make for some extreme EGT's with a stock turbo.
If you have a stock turbo and stock engine turn your Smarty down to level 1. Even then your EGT's will be high.

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Old Aug 21, 2019 | 09:48 PM
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I do have a monitor that includes EGTs.. I have never seen them go over 1200 degrees. I don’t have an LP gauge. I’m running an AIRDOG 150. The filter is about a year old and I drive this truck less than 10K per year. It could be the culprit. I’ll put a gauge on it and let you know what I learn. Thanks for your thoughts.
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Old Aug 23, 2019 | 09:16 AM
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Originally Posted by Creekflea
I do have a monitor that includes EGTs.. I have never seen them go over 1200 degrees.
Where is your temp sensor, pre or post turbo?
Back to morning brew . . .
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Old Aug 23, 2019 | 01:55 PM
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EGT probe is pre-turbo.
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Old Aug 23, 2019 | 02:55 PM
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Originally Posted by Creekflea
EGT probe is pre-turbo.

A stock 2003 Dodge Cummins will go to 1200+ EGT temps pre-turbo without even trying. The 2004.5+ stock engines will go to 1300+ easily.

I suspect your EGT gauge/probe is failing.

What are your boost levels?
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Old Aug 23, 2019 | 03:52 PM
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This is interesting. The EGT probe is fairly new. Less than 2yrs. The boost gauge looks normal. Ive never seen it go over 23PSI. One thing to remember. I am in Denver. THe altitude could keep that from going higher and closer to what you normally see. At idle I’m am reading about 5300PSI in the rails. I am told that is about normal. But I am wondering if I don’t have a bad sensor in the rail too. Thanks for all you ideas. I truly appreciate it.
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Old Aug 26, 2019 | 10:57 AM
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Originally Posted by Creekflea
This is interesting. The EGT probe is fairly new. Less than 2yrs. The boost gauge looks normal. Ive never seen it go over 23PSI. One thing to remember. I am in Denver. THe altitude could keep that from going higher and closer to what you normally see. At idle I’m am reading about 5300PSI in the rails. I am told that is about normal. But I am wondering if I don’t have a bad sensor in the rail too. Thanks for all you ideas. I truly appreciate it.

5k PSI rail fuel pressure at idle is normal. 23psi peak boost for a stock 2003 Dodge Cummins is low, even at high Denver alititude. Is your boost gauge a standalone or is that an OBDII reading?

1200 peak EGT's pre-turbo is really low. At high altitude, your EGT's will be higher since your boost will be less. I suspect your EGT probe/gauge is not reading correctly.
BTW, I'm in Calgary, 3500 feet above sea level.

Also, a stock 2003-04 Dodge Cummins runs lower rail pressure than the 2004.5+ engines.
A stock 2003-04 Cummins typically has 17-18kPSI peak. 2004.5+ engine will see 20kPSI peak.
A Smarty programmer will immediately set the rail pressure programming to the 2004.5+ levels. Plus more if you add pressure with the Smarty programming parameters.
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