rail pressure

[cerberusiam]

Yes, everytime.

Then why did you think you had a hard\no start problem?

 

[SWithrow]

Then why did you think you had a hard\no start problem?

This was a problem that slowly got worse over time and in December I would have to loosen and tighten the fuel line (on the rail or at the CP3) and the truck would fire up so I didn't think I was having a hard start issue I was having a hard start issue. My question is why with 160k on my truck & since new it has only produced 1500-1700psi during cranking it and it starts up with no problem. You have stated that it must have a min of 3000psi to rail.

 

[TCDiesel]

Ok Hrere"s the link YouTube - ‪railstart‬‎ If you watch closely and use the POP out for Motion 0. 2psi @ 32rpms /1. 5psi @ 32rpms/ 1. 5 @152 rpms (NO way starter is going to crank engine 152 rpms so its started) then it jumps to 4. 7psi @ 390rpms / then 7. 4psi @ 619rpms. then drops to 5. 3psi @747rpms in less then 1. 5 seconds.

 

[CSkal]

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

FWIW it was just a wild thought from the standpoint of cranking speed being more of an issue with diesel than gas due to higher compression with the CI vs spark. Had a no start on my tractor that related directly to cranking speed.

 

[cerberusiam]

NO way starter is going to crank engine 152 rpms so its started)

Are you sure about that? Most diesel engines require at LEAST 200 rpm's to even think about starting. I thought cranking speed on these engines was 250-280 rpms which sounds about right.



If you extrapolate the pressures and rpms assuming a consistent rise it puts start between 250-300 rpms and pressure. This is as granular as I can capture frames but that is because the data logger is not granular enough I think.



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[TCDiesel]

I can turn off the 3 banks and crank to check the RPMs, but this is not the only QI that I have seen the RPMS when Cranking W/ No-start,they are all MAX out at around 60 RPMs. My Logger shows the same, the data cannot be move to PC for some reason I cannot figure out, Maybe it don't like my 64bit-7. I always thought that it took More PSI and crank to start. . My experience tells Me they Don't need the Pressure or the high crank RPMs. I should disclose that these readings are from the aftermarket sensors. but I don't think it will change the readings on crank Pressure. It may take 3k to start in some engine(s), this one just does not require it. CRs are like women..... !!!!!!!!!!!!!!!!

 

[cerberusiam]

Be interesting to see what the cranking rpm's max out at.



Are you reading directly from these sensors to log the data or reading what the ECU is outputting?



Anyway to track what\if injectors are firing across the cranking range?

 

[MZuba]

I had time to play around with it a bit tonight, I borrowed a Snap on modis scan tool from a friend. I was reading about 1500psi when it would start, and about that pressure every time it started, but it still cranks longer than what it should. I read the codes in the ecm with this scanner, and it listed 3, 2 of them really have nothing to do with starting, but one of them, #P0251, reads" VP44 fuel valve feedback circuit" I am asuming it is some type of drain back or over pressure valve on the pump, any one have any ideas on this. A very reputable diesel mechanic in the area was suggesting to me before I found this code that the problem may be the pump, his suggestion was to replace the pump, feeling it is not building pressure fast enough and causing the long crank times. What do u guys think? And thanks again I appreciate the input from everyone!

 

[TCDiesel]

MZuba,You are the OP and Please feel Free to contact Me Todd Via Phone, I Just do not have the Time to answer every Question(s) By keystrokes I am much More Helpful By Phone.

 

[cerberusiam]

P0251 CP3 Pump Regulator Control



Thats a code for the FCA and it can cause hard starts if it is malfunctioning.

 

[MZuba]

To Cerberusiam, I unplugged the FCA and tried it, It does start the same way, then after it starts, it runs rough, and the pump sounds like its got rocks banging around in it, is that what you were looking for?

 

[cerberusiam]

Yeah, it went to max rail pressure with the FCA unplugged. Be interesting to see what your rail pressure is at that point to see if it maxing out where it should.



The code is for an FCA malfunction that could be effecting your start condition. Even thouhg it starts and maxes out it could still be sticking on the lower end of the pressure range and causing a hard start.



The code could also be a reaction to the CP-3 just not generating pressure like it should. That whole system is a bit of a black box when it comes to really testing out what is bad.



Could also be the COV is bypassing too much fuel on cranking. Frequently, the only wat to tell is swap parts.