Spratic rail pressure and loss of power

[basilry]

For the past few weeks Iv been getting intermitten power loss. The power comes and goes, one time driving the truck Ill hit 40psi with out trying and the next time I cant get over 18 and the truck wont get out of its own way. Iv replaced the CP3 regulator, and the Pressure relief valve and nothing has changed. I also added a Quadzilla rail pressure valve. One time driving Ill have pressure in the teens and the next time it wont get over 9000. Iv also had it as low as 1000 and had the truck kill coming up to a stop light. It always comes and goes but the last few days it has been getting worse. The truck idles at at 6000 pretty normally. What should I try next? Im going to swap out the rail sensor with a buddies tomorrow. Any suggestions we have a big snow storm comming and I need the truck to plow!!

 

[steved]

Doesn't the FCA also control the amount of fuel to the rail??

 

[Erik@LCD]

yup, post up the codes. The sensor seems likely to be the cause. Let us know what you find!

 

[basilry]

I swapped out the sensor and no difference. Im using my edge to read the codes and no codes are showing up. I just installed the quadzilla gage to help me try and solve the problem. So the problem existed before the gage when it. This morning when I got up to plow snow the truck fired and idled fine with no problems while it was warming up. I drove about 4 miles and the pressure was no higher than 9,000. As I slowed down for a stop light the pressure dropped to 1,000 and died. I got it started again as I was rolling after about 15 sec of cranking, Ran for another 1/2 mile and same thing, Killed. Once I was on the freeway the pressure stayed about 7000-8000 nothing higher. I ran around plowing and didnt get over 10,000 all day. Swapped out the sensor late in the day and ran it to the gas station. I got 18,000 out of it right away without trying and all the way to the J pressure stayed in the teens. I thought my problem was solved, let it idle at the J while fueling up and on the way back home, I didnt get over 8000. Any thoughts?

 

[steved]

Plugged filter?? If you can't supply the fuel to the CP3, it will starve.

If you replaced the FCA and the sensor, could it be the Edge itself???

 

[Erik@LCD]

could be the pressure relief valve. Try plugging it with a bolt.

 

[basilry]

I have 15 pounds of pressure at the cp3 pump so Im getting plenty of fuel to the pump. I also replaced the relief valve with a brand new one. I have a bolt but have not tryed to cap it yet.

 

[basilry]

Ohh, no matter what setting the edge is on it does the same thing.

 

[BMeier]

I have an '03 with similar issues, I am currently troubleshooting the problem. My rail pressure will be at 5500 psi when I first start it up in the morning. After a few miles the pressure will drop down to 6000 psi and back up to 10,000 going down interstate. When I stop at a light it will drop down to 2000 and back up to 5500 psi and had died once. I have a low fuel pressure light and a CAT fuel filter after the factory filter. The light would flicker so I hooked up a 0-25 psi pressure gauge and checked actual pressure, the lift pump pressure would be at 8 psi and drop to 0 psi and back up again. Well while troubleshooting the lift pump failed all together. I ordered another lift pump, will be here at the end of the week, we'll see if this fixes my rail pressure issue.

 

[basilry]

Just an update, I unplugged my edge system thinking that maybe that had something to do with my problem. Nothing changed, at first it was back to normal with pressure in the teens and then it dropped again to below 10,000. Anyone else experience this?

 

[basilry]

Another update, still have the edge unplugged and replaced the cam sensor because of a tac issue, maybe they are related at this point who knows. The new cam sensor didnt seem to change anything tho. I also replaced my fuel filter and water seperator on the fass pump. Still no change, works fine for a few minutes and then back to not working. The truck stalled on me 5 times this morning when i was on my way to go plowing. It seemed that if I didnt go on the freeway the truck would run ok just no power. It also started to "drive itself" every so ofter when the tc locked up and I would get off the pedal. I had to take and throw the truck in neutral to get it to stop. It is also taking longer and longer to get the truck to fire, at least 10 seconds of straight crainking until it fires and then the rail pressure gage gets maxed out and droppes to about 600 ish. Any other thoughts?? In the mean time Im waiting on a guy to scan the truck, I dont trust any of the area dealers and the truck is to new for the local cummins to read it. Thanks again

 

[Erik@LCD]

man, that is weird. I would suspect the FCA again. If you have another one to check it with, that might be a good idea. The issue with it driving itself concerns me. When that is happening, is the rail pressure spiking? If not, I would suspect that maybe there is an issue in the trans (converter or front pump).