max rail pressure at idle...2003 with all new parts

Out Back 4x4

Out Back 4x4

New member
Joined
May 12, 2011
Messages
242
Hey guys,

I have an 03 that has been at 3 shops over the past 3 and a half years getting repaired, modified, and repaired. My culprit at the moment is max rail pressure at idle. New fca (multiple), new dual cp3 controller, new cp3, one with 30k miles that was on the truck before modifying, new fca pigtail, all wiring has been tested/checked, injectors are brand new, fuel returning fine.

The shop it is at now and another technician from a dodge dealer have said they believe it might be the ecm. What are your thoughts before I throw more money at this dang truck. By the way, I am going to sell when fixed...just trying to figure this crap out after this long and lots of parts/money wasted.

Thanks
Jake
 
I had the same problem on a stock truck and it turned out to be the fca pigtail. There was no discoloration or anything, the pigtail appeared to be fine but it was junk.
 
Wires have been chased and continuity tested the mechanic said, he also changed out pigtail. Dealer tech says a driver might be bad in the ecm?
 
I had the same problem got to bad fca's in a row was mine but I found a diagnostic tip that if u unhooked the fca plug and put two pieces of down in the plug then connect a test light in the circuit an turn the key on and in 20 seconds after key is on the ECM will do a check an the test light will flash. That's how I check my ECM and wire's. Hope this helps.


Sent from my iPhone using Tapatalk
 
Cummins6.7trip said:
I had the same problem got to bad fca's in a row was mine but I found a diagnostic tip that if u unhooked the fca plug and put two pieces of down in the plug then connect a test light in the circuit an turn the key on and in 20 seconds after key is on the ECM will do a check an the test light will flash. That's how I check my ECM and wire's. Hope this helps.


Sent from my iPhone using Tapatalk
Click to expand...
Test lights are for non modulating 12v circuits.
Out Back 4x4 said:
Wires have been chased and continuity tested the mechanic said, he also changed out pigtail. Dealer tech says a driver might be bad in the ecm?
Click to expand...
Check voltage at the plug. If its 5v while idling then its not the ECM or the harness. If no voltage then probe wire at the ECM and check it there. If still no voltage then it is a bad ECM pin connection or the ECM itself. If you have voltage then the harness is the issue.
 
When the fca is unplugged, there is 5 volts, when you plug the fca in, there are 0.
 
Have you tried removing the belt. Then unplug the dual cp3 controler. Plug in just the stock cp3 only to eliminate the duals as the issue? 5v when plugged in would be the fca closed. 0v would be wide open explaining your high RP issue.
 
Which FCA? I would do as davem3261 said and eliminate the dual cp3 all together. The truck will run without belt and pump still plumbed up. If all is well then its obviously your controller/controller harness or a bad dual pump FCA. If all is not well then it sounds like you have got a bad bottom fca.
 
Mechanic just messaged me, he said he has taken the belt off and unplugged controller, same issue
 
Bottom FCA or pigtail. Its not unheard of to get a bad new FCA. I would switch the FCA on the pumps and leave the belt off the top pump. Then try it. Likelihood of having 2 bad FCA are slim. If it still does it then I need to know what was going on when this problem started. Random, were you working on the truck, driving or what?
 
Has the rail pressure sensor been checked or changed? Do you have an aftermarket rail pressure gauge?
 
I had the same issue on my 06 a while back, it was the FCA pigtail, new one from Jeff fixed me right up.
 
Sorry I am just getting back to this. I have an auto meter rail pressure gauge, I sent my pumps, injectors, controller and all sensors to be checked out and they all checked out fine. Truck started doing this after all the aftermarket work was finished, ran fine but the lift pump wasn't pushing more than 7 psi, so swapped lift pumps, running between 15 and 17 now and that's when problem started. Found out the previous guy plumbed the returns wrong and it wasn't returning enough fuel. Now that it's returning fine with no restrictions, the problem still persists. If I remember correctly my mechanic said that on the scanner it was calling for correct amount of rail pressure but it maxes out after a split second and then we shut the truck off.
 
UN hook the rail pressure gauge and try it. I have seen them go haywire several times. Also like Ben said above, what's rail key on engine off?
 
If you have 5 volts unplugged and then 0 plugged in, you're dropping voltage. Try unhooking the harness from the ecm and fca, then load test the wires. You may have a damaged wire that can show 5 volts on a scope but it can't carry a load.
 
Mechanic said he tested the wires. Rail pressure gauge has been unplugged for a while. Just monitoring with scanner. Ecm is out now. Don't know if I should order one or not...nightmare of a mess.
 
You must log in or register to reply here.
Back
Top