[JAMES VASQUEZ]

So my rail pressure drops when my thermostat opens @ 190*.

At idle the rail is running @ 6.7k 6.8k. When im running down the road and the motor warms up and the thermostat opens the rail pressure drops off to around 5k 5.5k real low. Sometime it will get as high as 10k but thats if im lucky.

But before 190* the truck runs amazing, like theres no problem what so ever.

I plugged the relief valve to make sure the fuel wasnt being sent back. But no change in the rail pressure.

I know ive got fuel going to the injection pump. Installed a guage last night.
- autometer fuel pressure

i know the turbo is good replaced that last night.
- industrial 62/80

replaced injectors bout 8 months ago.
- 60 hp idustrial injectors

injection pump bout 3 years ago.
- factory industrial

any help would greatly be appreciated.

 

[waywardtravel]

Does your truck start a rough idle at the same time or any other symptoms? smoke? smell from the exhaust.

If no smoke and rough idle I'd re-torque the connector tubes.

 

[JAMES VASQUEZ]

Does not rough idle sounds fine. Runs fine until 190*. When i park and the turbo timer is running till shut down it idles fine.

Ive put a wrench on the lines none of them were loose, none were makeing noise like when the bracket is loose. Didnt notice anything out of the ordinary.

Before the coolent gets to 190* it black smokes like normal.
After 190* sometime it blows like a greyish smoke but its not alot like the black smoke.

And one time couple weeks ago, at idle it did seem to puff some grey smoke and smelt like diesel but it was only the one time before the turbo timer cut off. But it wasnt alot. Wasnt thick.

My buddy saw it said something about it but said his truck did the same thing. So idk.

 

[Irish Maniac]

When its at temp and the rail pressure is low does it idle rough or anything? What kind of rail press gauge are you using?

 

[JAMES VASQUEZ]

No rough idle runs fine before 190* @ 190* rail pressure drops off

using edge cts

before pressure drops off it runs like a champ. Great throttle response. When i hit the gas it takes off.

When pressure is low and coolent is @ 190* or higher it still goes but the throttle response is slow and it slow climbs. But when its gaining speed the egt's go through the roof. 1400* 1450*. And boost goes almost immediatly to 40 psi

before 190* no abnormal rise in egt's or boost

 

[MegaB]

I thought i just read a post in the last few days of someone who was having a similar problem . I believe they changed the water pump and solved the issue . Search it , you may find your answer . Good luck , Brian .

 

[JAMES VASQUEZ]

I replaced the water pump bout a yr ago give or take. I noticed a little water on the ground the other day but nothing else had water on it. Ill def check that out.

Do you remember what the thread was called or what i could search for to see what the other guys problems were.

Thanks

 

[Irish Maniac]

Regardless of when you changed parts they could still be bad. Where did you get the waterpump? there have been quite a few guys on here who have installed new waterpumps and had them fail quickly. I wanna say some were NAPA ones but I cant say for sure.

 

[JAMES VASQUEZ]

I understand that, that happens. I guess i dont understand the coralation between the water pump going out and the rail pressure dropping at 190*

 

[KMKDIESEL]

I replaced the water pump bout a yr ago give or take. I noticed a little water on the ground the other day but nothing else had water on it. Ill def check that out.

Do you remember what the thread was called or what i could search for to see what the other guys problems were.

Thanks

I believe it just said low rail pressure as the topic

 

[MegaB]

Yeah , i dont understand the relationship either , but if it gets you going its worth looking at . Ill double check some recent posts and get back to you tonight .

 

[JAMES VASQUEZ]

That would be very helpful

 

[MegaB]

Found it . http://www.cumminsforum.com/forum/3rd-gen-powertrain/535347-help-rail-pressure-hell.html

 

[MegaB]

His symptoms are kind of similar to yours . I find it very odd that the water pump can cause this , but what ever works . Like i said before , its worth looking into if it gets you going . Good luck , Brian .

 

[JAMES VASQUEZ]

yes thank you very much always open to anything

 

[Elsorrell1982]

yes thank you very much always open to anything

I know this is old thread but did you ever figure out a solution?? My truck is doing the exact samething i've replaced fca, pressure sensor, plugged relief, changed filters ect i do occasionally get code p0251 and have changed fca 3 times with no change only time it throws code seems like sitting at a light or drive through line it will stumble like its gonna die and go right back to smooth idle and that may happen once a week the idle pressure is always around 6500 no matter but when it warms up ive had it drop as low as 3900 on highway and gutless but like yours before the water temp gets to 190° it has all the power and rail pressure will run up in the low 20000's no problem. Also some days it will run great all the way to town and then on the way back it will mess up or vice versa but seems to act up more and more but still never before its warmed up the water temp.

 

[rghavana]

I would check/monitor demanded vs actual rail pressure to help rule out ECM /electrical issue.
P0251 should try go thru all diagnostics for code, just throwing parts at issue will not fix it if wiring issue.
When issue happens briefly, unplug FCA should get max RP 24kpsi ++

possible causes for P0251
FUEL PUMP
(K181) FUEL CONTROL ACTUATOR DRIVER OPEN
(K31) RETURN CIRCUIT OPEN FROM FCA TO ECM
(K181) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO EXTERNAL VOLTAGE
(K31) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO EXTERNAL VOLTAGE
(K31) FCA RETURN CIRCUIT SHORTED TO (K181) FCA DRIVER CIRCUIT
(K181) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO GROUND
(K181) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO ANOTHER CIRCUIT
(K31) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO ANOTHER CIRCUIT
INTERMITTENT CONDITION
ECM

 

[Elsorrell1982]

Rghavana,
Awesome thank you i will go through the checks. A buddy just this morning emailed me a copy of the service manual with all the detailed list of where to start ,wire locations/colors ect. So thats a good place to start if i have any troubles ill check back in this evening and let ya know what i figure out!! Thank you