Fuel Rail Pressure low - Chevy and GMC Duramax Diesel Forum
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Old 07-30-2013, 01:49 PM   eBay Motors  #1 (permalink)
 
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Fuel Rail Pressure low

Hoping someone can give me some a solution. I have an 03 duramax that was running fine until one hesitant start, 5 seconds of cranking and it started, drove 5 mi home, checked wot to see if filter may be clogging, but no problem. Turned off engine ...5 hours later no start...cranks fine, scan tool says FRP 43...I get 2, check filter, no air, filter was clean. Air pressure in tank bled half a gallon at the filter in 30 seconds...Is their some electrical component that could suddenly fail that would keep the injectors from opening? Such as the fuel regulator?
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Old 07-31-2013, 04:15 PM   eBay Motors  #2 (permalink)
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Moving to LB7 for more help-!

You need to scan the systen for stored codes. That will help diagnose the problem.
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Old 07-31-2013, 04:18 PM   eBay Motors  #3 (permalink)
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Some more diagnosis should be performed to see if there is enough fuel pressure to fire it up. Any other things going on electrical wise like on the dash or anywhere?
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Old 07-31-2013, 05:38 PM   eBay Motors  #4 (permalink)
 
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I'm new here so still trying to follow along, I have run a scan tool once it gave a low FRP reading I believe it was looking for 43 and it said 2 and it cranks fine but no fuel is getting in the cylinders and no hint of fire. So now I drained the tank and have flushed the remaining fuel from the tank through the filter housing and it ran through with very little air pressure. I have no air leaks or fuel leaks previously and the only thing that seems to be a constant factor is when injector cleaner is introduced into the system it causes problems. I had injectors replaced twice before, hence the reason for draining the tank and starting fresh. Failure to start this time was sudden with no warning. Can the FRPS sensor give a faulty reading that would cancel the electrical signal going to the injectors? Because it was running fine when I shut it off I wouldn't think the relief valve could be stuck open because it worked fine prior to turning off. Is it possible for something in the Cleaner to dislodge sediment in the system after the filter sufficient to clog or hinder the injectors? Thanks for all the answers I can get.-Danny
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Old 07-31-2013, 05:52 PM   eBay Motors  #5 (permalink)
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I'm not sure if your scan tool has the ability to run the tests needed to help pin point the problem. You need to read your rail pressure while cranking the motor to see what it is at. I believe it is supposed to have atleast 5500psi for it to start.
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Old 07-31-2013, 10:58 PM   eBay Motors  #6 (permalink)
 
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Scanner is a snap on, I was told each number is mpa? X 145 so 43 X 145 =6235 psi my reading of 2 would be 290 psi ..that not being in the range of operation needed, the injectors will not get any signal to fire...if I understand correctly. I have searched through tons of threads hoping to find someone who has encountered the same or close so I don't throw parts at it unnecessarily but every case has a different twist and I have yet to find any place that can bench test parts as I live 60-70 mi from service. Oh and electrical ..nothing except my dash panel goes out after running for a while but only after I shut it off, then restart, they don't come back on for a while if everything is good and warmed up...one time drove about 60 mi before they came on. Never had them go out while driving.

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Old 08-01-2013, 08:50 AM   eBay Motors  #7 (permalink)
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Quote:
Originally Posted by redneck6821 View Post
I'm not sure if your scan tool has the ability to run the tests needed to help pin point the problem. You need to read your rail pressure while cranking the motor to see what it is at. I believe it is supposed to have atleast 5500psi for it to start.

ECM/FICM needs to see at least 10 MPa (1,450 psi) in order to fire the injectors.


Quote:
Originally Posted by dmtech View Post
Scanner is a snap on, I was told each number is mpa? X 145 so 43 X 145 =6235 psi my reading of 2 would be 290 psi ..that not being in the range of operation needed, the injectors will not get any signal to fire...if I understand correctly. I have searched through tons of threads hoping to find someone who has encountered the same or close so I don't throw parts at it unnecessarily but every case has a different twist and I have yet to find any place that can bench test parts as I live 60-70 mi from service. Oh and electrical ..nothing except my dash panel goes out after running for a while but only after I shut it off, then restart, they don't come back on for a while if everything is good and warmed up...one time drove about 60 mi before they came on. Never had them go out while driving.
Demand at startup should be around 43 MPa but if you're making only 2 then something is definitely not right.

Possibilities
1) Fuel supply issue (run a temp clear vinyl line between filter head and FICM, then look for air bubbles)
2) Injector returning too much fuel (check your fuel return line while cranking, if fuel is gushing out you have an issue)
3) Bad FPR (need to replace to verify issue)
4) CP3 pump toast (you can have it tested but I would suggest to just replace since it will include a new FPR as well)
5) Bad rail pressure sensor
6) FPRV not holding pressure
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Old 08-01-2013, 12:05 PM   eBay Motors  #8 (permalink)
 
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Originally Posted by MTL_Dmax View Post
ECM/FICM needs to see at least 10 MPa (1,450 psi) in order to fire the injectors.




Demand at startup should be around 43 MPa but if you're making only 2 then something is definitely not right.

Possibilities
1) Fuel supply issue (run a temp clear vinyl line between filter head and FICM, then look for air bubbles)
2) Injector returning too much fuel (check your fuel return line while cranking, if fuel is gushing out you have an issue)
3) Bad FPR (need to replace to verify issue)
4) CP3 pump toast (you can have it tested but I would suggest to just replace since it will include a new FPR as well)
5) Bad rail pressure sensor
#2 Could one injector be responsible or would it need to be several for the pressure to drop that much? #4 My Cp3 pump was replaced 30k ago and shouldn't dump on a key off/key on situation should it? I'm leaning towards #3 or #5....Thanks
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Old 08-01-2013, 12:54 PM   eBay Motors  #9 (permalink)
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Originally Posted by dmtech View Post
#2 Could one injector be responsible or would it need to be several for the pressure to drop that much? #4 My Cp3 pump was replaced 30k ago and shouldn't dump on a key off/key on situation should it? I'm leaning towards #3 or #5....Thanks

It is possible for multiple injectors to drop the rail pressure way down especially if you got a load of bad fuel. I also added a #6 FPRV because that may be stuck open and draining your rail pressure off as fast as you can make it. Assuming the fuel supply side is good, I would first check your fuel return while cranking and see how much fuel is coming out......if it's a lot, then you'll need to track down where it came from (injector, CP3 or FPRV). Otherwise it's probably either your FPR, CP3 or the rail pressure sensor.
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