rail pressure

[MZuba]

Hi can anyone tell me what the correct rail pressure should be on my 03,during crankingit over to start. I have a starting issue, with long crank times, I replaced the rail pressure sensor and it is better. I am trying to find out if the cp3 pump is weak. Also where is a good place to get a gauge to measure the rail pressure?

Thanks

 

[DBraswell]

I am having the same problem. I replaced the rail sensor and fca, seems to start ok when it is cold but after the motor is warm its hard to crank. but when it is runing it is fine. I know suspect a injector.

 

[TCDiesel]

Cranking, 1300-1700 minimum for injector pulse.

 

[TCDiesel]

Hi can anyone tell me what the correct rail pressure should be on my 03,during crankingit over to start. I have a starting issue, with long crank times, I replaced the rail pressure sensor and it is better. I am trying to find out if the cp3 pump is weak. Also where is a good place to get a gauge to measure the rail pressure?

Thanks

You will need a digital gage for cranking Pressure or adequate scan tool.

 

[cerberusiam]

Minimum cranking psi at the rial should be 3000 psi or better. If it can't make that it usually means hard starts. You will need a guage like Isspro makes to read rail pressure, or, a scan tool that is capable of reading the ECU outputs thru the data port.

 

[TCDiesel]

It will pulse way before 3000 psi. If you want to remove the injector relay(s) it will crank up and beyond 3k.

 

[TCDiesel]

The unknown Question,What PSI will good injectors pop off at.

 

[cerberusiam]

It will pulse way before 3000 psi. If you want to remove the injector relay(s) it will crank up and beyond 3k.

I have no idea what you are talking about, there is no way to effectively measure and injector pulse pressure so it doesn't compute. Unless the rail develops at least 3000 psi with the starter the engine simply won't fire. Not sure if its because the ECU simply doesn't fire them or without thta much pressure the injectors do not fire an adequate pattern to ignite. With the lack of white smoke on most of these no starts its a good indication the injectors are simply no firing and are just bleeding pressure which is maybe what you are referencing.



If you remove the injector relays the injector doesn't fire.



How about unplug the FCA and allow full fuel to the high pressure circuit of the CP3?

The unknown Question,What PSI will good injectors pop off at.

Since CR injectors don't really "pop", maybe a better question is what rail pressure is adequate to effectively fire the injector?



By effectively fire the injector I mean adequate pressure to lift the pintle off the seat fast enough and long enough for required duration to inject enough enough fuel for combustion.

 

[TCDiesel]

I guess a video demonstration needs to be arranged, to show What I mean,I will see if I can download the video to our site and post the Link. I am just to tired to to it tonight, Maybe tomorrow evening!!!

 

[Prairie Dog]

Cool, that will give me time to make popcorn

 

[cerberusiam]

Cool, that will give me time to make popcorn

:-laf:-laf

 

[EDankievitch]

Any one know how to convert KPA to Psi ????? My scann tool only reads in KPA at start up it's around 45,000 and up and running it's 28,000 KPA under full load... .

 

[cerberusiam]

1 Kpa (Kilopascal) = 0. 145037738 Psi (Pound Per Square Inch)

 

[EDankievitch]

Thanks, I knew I should have stayed awake in math class

 

[CSkal]

Just a thought, does it crank faster when cold and slower when it is hot?

 

[MZuba]

CSkal, to tell you the truth, I don't really notice a difference in cranking from cold to hot, what are you contemplating, on that? a starter problem, or something else?
Thanks, Mike

 

[MZuba]

To tell you the truth, I haven't noticed if it cranks better either way, do you have any idea of something?

 

[SWithrow]

Minimum cranking psi at the rial should be 3000 psi or better. If it can't make that it usually means hard starts. You will need a guage like Isspro makes to read rail pressure, or, a scan tool that is capable of reading the ECU outputs thru the data port.

I had the same question back in the fall due to hard starts. I was quoted the minumum of 3k. My stock CP3 on crank was around 1500psi. I replaced the CP3 with a Stage1 and new sticks and still get between 1500-1700psi and the truck fires up everytime and have no issues. Where does it state that you need a minumum of 3k?

 

[cerberusiam]

I had the same question back in the fall due to hard starts. I was quoted the minumum of 3k. My stock CP3 on crank was around 1500psi.

Would it start at that psi?

I replaced the CP3 with a Stage1 and new sticks and still get between 1500-1700psi and the truck fires up everytime and have no issues.

Throw out all the numbers for minimum pressure as it applies to your truck. You negated all that with the upgraded parts.





IIRC, the 3000 psi is out of the Bosch manuals on the HPCR system. Will it start at less? Probably but there is no good way to tell what that is. The hard\no starts I have seen were all under 2000 psi, 1500-1700 psi. Once you get 2800-3000 psi they seem to start fine.



MZuba, you need a peek at the cranking rail pressure to see what it is doing. If it is low there are multiple sources. Like I said, unplug the FCA and see if that makes a difference and go from there.

 

[SWithrow]

Would it start at that psi?

Yes, everytime.

Throw out all the numbers for minimum pressure as it applies to your truck. You negated all that with the upgraded parts.

Still gets between 1500-1700 on crank and 6000 at idle, same numbers as before.