P0251 Irratic Rail Pressure

[TCDiesel]

Interesting, how long have you had it in there?



About the only thing I can think of is its bypassing more fuel than it supposed to and dropping case pressure. That would mean the spring is broken or worn, possibly a plunger problem.



I wonder how many other rail pressure issues could be a simple COV failure?

Many... ... .

 

[JJPage]

Glad to hear the troubleshooting is going well.

Interesting, how long have you had it in there?



About the only thing I can think of is its bypassing more fuel than it supposed to and dropping case pressure. That would mean the spring is broken or worn, possibly a plunger problem.



I wonder how many other rail pressure issues could be a simple COV failure?

I have had the Arson kit since last July, but only about 3500 miles since installing it.



I put the Arson FCA back in today and rail pressure went back to 4/5k at idle, whether in gear or not, it is bouncing and cannot get more than 23k @ WOT. I swapped cascade valves back and forth on the side of the road, little if any difference. Got home, put the stock FCA back in with the Arson cascade valve and the rail pressure is stable, back to 6k at idle and will hit and hold 25+k rail pressure.



Shane had me exercise the spring and plunger on the cascade valve, to make sure it was moving free and not sticking, it seemed to move in and out about 3/8" without any hesitation, and I did that before swapping it back in so... .



Shane is sending a replacement FCA, the spring coils inside the plunger looked uneven from side to side but it appeared to be centered, really hard to tell looking through that little hole with a flashlight.



I may have more than one issue here, but Shane is being supportive and that is always a plus. On a side note, He told me that P0251 code can show up if you unplug the FCA while engine is running.

 

[DAVID@DBR]

I don't know if you have figured your problem out yet but i have had two trucks wear me out with the same type symptoms and they were both two different problems. The first on was a bad connector to the FCA. The factory spades had to be tightened because they were not getting a good contact. Guess it happened from being unplugged so many times. The second was the injector tubes. They were tight and not "leaking" but at some point someone had destroyed tips, thus they were not seating well in the injector. Both of these issues cause very erratic rail psi. Hope this helps...

 

[JJPage]

Shane/Wicked called me yesterday, he received the FCA I sent back to him. He said it appeared to be working correctly, but the internal spring did look a bit abnormal, he is going to send me a new one.



I will double check the connector, when I replace the FCA, Thanks.



It has been running fine with the factory FCA this past week, in fact Saturday it dynoed 594hp at Shelly's in Spokane, it set the brake and ABS lights off in my dash, but no codes... . so I cleared the codes that were not present:-laf, with a borrowed Smarty, and the lights went away?

 

[JJPage]

Fed Ex delivered my Replacement FCA yesterday, Friday 2/19/10, installed last night before dark.



Drove over 120 miles today ,several WOT runs, both from rolling 15mph, and 60 mph 4th gear locked tc. Tried two Smarty softwares, 411 and 313V_DR55TNT. All is good, no issues.



Thanks Shane/Wicked Diesel.

 

[AH64ID]

Glad its working normal again!

 

[JJPage]

Thanks, me too.



What I found interesting, at 60mph in 4th, locked tc (1500RPM), Smarty 411, roll into WOT would hit 25k rail pressure, then would drop to 20k until 1900rpm, then it would hit 25k, and hold it until I let off. I repeated this several times.



TNT, WOT starting at 60mph in 4th gear tc locked, would hit 26k+ rail pressure and hold it well past 3000rpm until I backed off.



411 SW9, TNT SW7 TM4 TQ4 RP1, ..... 411 was draining my rail early, causing higher egt's by fueling heavier, yet TNT was definitely stronger throughout the rpm range.



I wonder if 411 on SW7 may be stronger with lower egt's than SW9?



Truck is bangin on all 6!

 

[CoastyAV8R]

I've been able to borrow a friends COV in my truck for the last few days while his is torn apart and the truck has been starting normally again. I compared my COV to my buddy's and there really wasn't a discernible difference although I thought the spring in mine seemed softer than in his but I don't know. I'm going to keep it in there until his truck is ready to run again to see how it does with it to make sure it's the long term fix.

 

[JJPage]

I've been able to borrow a friends COV in my truck for the last few days while his is torn apart and the truck has been starting normally again. I compared my COV to my buddy's and there really wasn't a discernible difference although I thought the spring in mine seemed softer than in his but I don't know. I'm going to keep it in there until his truck is ready to run again to see how it does with it to make sure it's the long term fix.

I am going to pack my factory cascade valve along with the rest of my spare parts underneath my back seat. Serpentine belt, lift pump, gearcase pump, fca, boost hose, fuel filters... . isn't it fun owning one of these rigs:-laf.



Her is a link to purchase a new COV: Common Rail