P0251 Irratic Rail Pressure

[JJPage]

While cruising about 35mph, my truck almost died and then recovered, a couple of times. I noticed my rail pressure fell to zero and then jumped back up, as long as I fed it fuel it was ok, let off, it would drop to zero and stutter, and then quickly recover.



It is no longer dropping to zero, but rail pressure is only 5k at idle, if i put the trans in Drive it jumps to about 6k. While cruising at any speed if I let off, rail pressure will drop to 4k, WOT was low also, 23k, Usually steady 25/26k.



My rail is capped, Arson III kit. I replaced the modded FCA with my stock FCA, disconnected the EZ and the TST, Smarty back to stock. The rail pressure is now steady but still low, except at WOT it is back to 25k. I thought my Walbro may be dying, it's running but it does change pitch in sound... I believe because the grid heaters are cycling. I tried pinching the return line on the Walbro while idling to see if rail pressure would increase, Bad idea, lifted the plastic cover off the fuel filter canister I guess my lift pump is ok.



So now I am at a loss, I found two definitions for the P0251;



INJECTION PUMP FUEL METERING CONTROL "A" MALFUNCTION and



INJECTION PUMP FUEL VALVE FEEDBACK.



Since I installed the stock FCA I have not generated the P0251 today, but rail pressure is still low at idle 5k and drops to 4k if I let off while cruising.



Could this be a rail pressure sensor, tps??? Any suggestions would be appreciated. Thanks, Jess

 

[blacksheepdiesel]

What is fuel supply psi?

Godspeed,
Trent

 

[JJPage]

I do not have a fuel pressure gauge, I know... .



But if the Walbro is pushing enough pressure to pop the lid on the fuel filter canister, and also maintain 25k @ WOT, I believe the lift pump is ok.



I have capped my rail, but with a solid bolt the same length as the banjo bolt, so maybe the relief valve has opened and fuel is getting by the solid bolt. I remember back when everyone first started capping rails, they were using a long enough bolt to hold down the valve, not just blocking flow. Does anyone know the correct length for that bolt?



I am also going to re-check the torque on all my cross tubes, I did notice some fuel residue along the top of the block from between #3 and #4 injectors to the back of the block.



What does P0251 "INJECTION PUMP FUEL VALVE FEEDBACK" mean? Is this the Rail Pressure Relief Valve?

 

[blacksheepdiesel]

Good idea on checking where the fuel residue is coming from.

Do you have a buddy who would let you try his relief valve and see what happens?

Godspeed,
Trent

 

[TCDiesel]

You are more than welcome to use our Test Sensors ndennis has them at Present send PM and he will forward to you. It generally means sensor is bad or your cascade valve is on its way OUT... means New valve. The pump must be tore down to replace.

 

[JJPage]

Good idea on checking where the fuel residue is coming from.



Do you have a buddy who would let you try his relief valve and see what happens?



Godspeed,

Trent

Not sure If I can borrow one or not... . I would rather just make sure mine is capped proper.

You are more than welcome to use our Test Sensors ndennis has them at Present send PM and he will forward to you. It generally means sensor is bad or your cascade valve is on its way OUT... means New valve. The pump must be tore down to replace.

That's very generous of you, Thanks, I may have to take you up on that.



Which sensor? Rail pressure sensor? I thought I installed a new cascade valve with Wicked's Arson III kit, at least thats what they called it, and it was external, they sent me two new fittings, one thats on the top of the CP3, has a silver ball in the center of it, and one that was for the inlet feed, it had a modified "stem" which held a little check ball in the pump. . I still have the factory ones, should I change them back out also?



Just an FYI , my 03 just turned 25k on the odo, so the internals of the CP3 should be in good condition, Have w/f seperator, 2mic and 7 mic filteration.

 

[AH64ID]

Is the Cascade valve common to go out?



Do any of the CP3 upgrades include a new one?

 

[TCDiesel]

JJPage. Yes put the factory Back IN. The reason I say to break it down is BC the manifold May be plugged, thier are 3 in the Kit ,LV. FCA,Sensor.

 

[JJPage]

Is the Cascade valve common to go out?



Do any of the CP3 upgrades include a new one?

AH64ID, Thank you for following my problem and helping out, here is a list of the Arson kit;



WICKED DIESELS, WICKED DIESEL



Jess

 

[AH64ID]

AH64ID, Thank you for following my problem and helping out, here is a list of the Arson kit;



WICKED DIESELS, WICKED DIESEL



Jess

Thats the kit you have correct?



I would consider calling them back on monday for some more diagnosis. . They seem to have been providing good service thus far.

 

[JJPage]

JJPage. Yes put the factory Back IN. The reason I say to break it down is BC the manifold May be plugged, thier are 3 in the Kit ,LV. FCA,Sensor.

Which one? The one on top of the CP3? Or the one where I have to raise the back of my truck 4' off the ground so the check ball does not fall out?#@$%!



I believe I know what your going to say..... :-laf:{:-laf It's January and I have no garage, that my truck will fit in.

 

[TCDiesel]

No . . the cascade valve is not in the Kit...

 

[JJPage]

Thats the kit you have correct?



I would consider calling them back on monday for some more diagnosis. . They seem to have been providing good service thus far.

Yeah, I have the Arson III, when I spoke to Shane on Friday I did not know I had any codes. There are a few things I need to make sure of first, like my cross tubes and relief valve, before I start out in the wrong direction of pointing fingers and casting blame, because Wicked has been very good as far as Customer Service, and I believe they will continue to do so.

 

[TCDiesel]

Number 28... ... .

 

[JJPage]

No . . the cascade valve is not in the Kit...

Number 28... ... .

You have me a bit confused... But,

Yes #28 is in the kit, I still have the factory one, I will put the factory one back in, first thing in the AM. Thanks.

 

[JJPage]

OK, I installed the factory cascade valve and my rail pressure is back to 6k at idle in neutral and jumps to 7/7. 5k when I place in gear.



It's raining out so I'm not about to do any WOT runs, but it appears it is back to normal. I still have the factory FCA in place also, so I do not know how it will respond with the Arson FCA, if this weather will let up, I'll change it back and see what it does.



I am going to check in with Shane at Wicked tomorrow, see what his thoughts are.



Thanks to all, for your help. Jess

 

[TCDiesel]

You have me a bit confused... But,

Yes #28 is in the kit, I still have the factory one, I will put the factory one back in, first thing in the AM. Thanks.

I did not see it in the link picture.

 

[JJPage]

I did not see it in the link picture.

You have to scroll down to the bottom, it shows it there. What goes wrong with a cascade valve?



Thanks again TWest, you saved me a couple of hrs retorqing my tubes out in the weather, although that's still not a bad idea. Jess

 

[AH64ID]

Glad to hear the troubleshooting is going well.

 

[cerberusiam]

What goes wrong with a cascade valve?

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?