Max rail pressure at idle, NOT fca

ATTABOY

ATTABOY

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Joined
Oct 19, 2009
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I've got a problem that's driven me crazy, I have max rail pressure at an idle threw all RPM's, I've read slot that pointed toward FCA as the problem, I swapped my buddies FCA with mine and no change, I've even unplugged FCA while running and no change in pressure.
I'm showing codes P0251 and P0088, my first ? is what is the difference in metering control "A" or "B"?? Second ? is anyone know what the voltage should be at FCA at idle and where that comes from, ECM?? where should I look next? I really don't want to spend the money to have dealer scan it.

Hope someone can help

Oh and the truck runs real good it's jus hard to manage at low speeds and RPM's, not to mention the noise it makes!!
 
And I'm just starting here so if I'm doing something wrong with posts let me know
 
Did you recently do a cp3 diy? If not then maybe someone else will chime in.
 
Yes, put new motor and CP3 in truck couple months ago, been doing it ever since
 
Possible Rail Pressure Sensor failure...I wouldnt drive at full rail pressure at all. Its killing your injectors.
 
That's the sensor on the rail next to PRV, right? Is that where the FCA gets it's signal?
 
ATTABOY said:
That's the sensor on the rail next to PRV, right? Is that where the FCA gets it's signal?
Click to expand...

Yes, next to the Rail valve. No, the RPS sends a signal to the ECM and from the ECM RP is adjusted via the FCA. So with a bad /no signal from the RPS, the ECM throws full RP signal to the FCA.
 
Shane from wicked is one of the guys I was hoping would chime in. He should be able to figure it out for ya.
 
Shane? He works at wicked diesel? The shop that makes that arson kit for CP3?? can I jus call the shop??
 
If you've been driving for 2 months @ full command RP you might need to pony up for new stix.
 
I haven't been driving it, just tryin to avoid dealer by figuring it out myself, I know max pressure is bad on parts
 
Swap the rail pressure sensor out and see if that fixes it. A simple change and cheapest if its the problem.
 
Easiest way to test rail pressure sensor is to get a scan tool that will read the sensor voltage. See what the voltage is when the connector is plugged in, key on, engine off, then unplug the sensor. should go right to 5 volts. if the voltage with the connector plugged in is just under 5 volts with the key on, engine off, the rail pressure sensor is bad. If it is right at 5 volts then you have a wiring or ECM problem possibly. rail pressure sensors aren't cheap so i wouldn't just throw one at it.

If you dont have a scan tool you'll have to find which wire is the 5 volt reference and which wire is the signal wire and tap the signal wire with a volt meter to watch it. the 3rd wire is a ground i believe. I am not at work and i dont know the pinout on that connector off the top of my head.
 
Found it, the plug from harness to FCA was bad, making no connection. Changed the plug out from extra harness and it perfect again. thanx for all your help guys!!!
 
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