Rail Pressure ?s
06-21-2007, 09:20 PM
#1
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Rail Pressure ?s
Ive been trying to figure out a long crank issue with my truck Ive tryed several things and nothing is making it any better my question is how low should my rail pressure go after the truck is shut off it goes to 0 in almost no time I would think it should hold some pressure. If anyone has any suggestions please let me know. Thanks
06-21-2007, 09:30 PM
#2
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Well mine and I suspect most are electric. If the gauge is powered with key on power then it should drop to 0 or is not reading when key is in off position.
I can always be wrong though.
AS I STATED I COULD BE AND WAS WRONG!
Both my Autometer electric fuel pressure gauge and my Diprocol Rail pressure gauge freeze at the last reading when the key is turned off. They stay at that reading until power is applied when turning the key on. Then they drop to 0 and will come up to actual pressure reading after a few seconds of the truck starting.
I can always be wrong though.
AS I STATED I COULD BE AND WAS WRONG!
Both my Autometer electric fuel pressure gauge and my Diprocol Rail pressure gauge freeze at the last reading when the key is turned off. They stay at that reading until power is applied when turning the key on. Then they drop to 0 and will come up to actual pressure reading after a few seconds of the truck starting.
06-21-2007, 09:42 PM
#4
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See my corrected post above. I don't know about the DRBIII reading, but I would think unless the rail pressure sensor has power that it is not going to read valid numbers. Does the DRBIII have rail pressure test that you are performing when off??
06-21-2007, 10:58 PM
#5
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As soon as you cut the key off, the rail sensor is losing its 5v feed and there is no way to get an accurate reading from it unless you are reading it with key on/engine off. It could be the rail relief valve or an injector leaking if it isn't holding any pressure. I'll try mine tomorrow with my DRBIII and get an idea of what it is doing. I am thinking it should hold some pressure too.
06-21-2007, 11:06 PM
#6
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According to the FSM ith should read lower than 870 psi or it can set a code. I haven't been able to find out what it should actually read though. Will find out what mine reads in the AM.
06-22-2007, 05:11 AM
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This is with the engine off ignititon on and I dont use a relief valve I have a dual feed line. I dont think it is an injector I have run an injector return flow and it is way under the maximum for return and it doesnt smoke white at all or run rough so I wouldnt think it is bleeding out into the cylinders. Sometimes it will crank for 10 or 15 seconds before it will fire.
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06-22-2007, 11:45 AM
#8
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The rail is a self bleeding system....meaning when you shut the truck off, it is supposed too bleed the pressure off.
Your long crank however sounds like you could have a cracked nozzle(s).
Your long crank however sounds like you could have a cracked nozzle(s).
06-22-2007, 04:53 PM
#9
DTR's 'Go to Guy'
FWIW
Mine has no driveability problems or long cranks and key on engine off reads 0. Shutting key of and back on real quick ( engine off) shows rail bleeding down to 0 within about 3 seconds.
Mine has no driveability problems or long cranks and key on engine off reads 0. Shutting key of and back on real quick ( engine off) shows rail bleeding down to 0 within about 3 seconds.
06-22-2007, 11:30 PM
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Maybe it has the 06 G56 long crank bug....
Just out of curiosity, what happens when you dont crank for that long, instead just try a couple of 3 sec bursts or so. Does it fire up, or do you have to crank it for that long regardless?
Just out of curiosity, what happens when you dont crank for that long, instead just try a couple of 3 sec bursts or so. Does it fire up, or do you have to crank it for that long regardless?
06-22-2007, 11:38 PM
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It has always had a somewhat of a long crank longer than most trucks anyway but every since I put the II stage 2 pump with the dual feed line it is worse sometimes it starts fine and some times it cranks for 10 to 15 seconds or more.
06-22-2007, 11:41 PM
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Can you tell me how long it takes for your rail pressure to come up when mine does the super long crank it takes forever to build up pressure.
06-23-2007, 01:26 PM
#13
DTR's 'Go to Guy'
Cranking went from 0-9 psi in under 3 seconds on the feed guage- Commander- and at the rail pressure went from 0 to about 3900 when it started. Again , all in about 3 seconds. Immediately after starting the rail went to 5500 psi at idle. Same readings on the DRB and the Commander.
06-23-2007, 07:22 PM
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Well I checked rail pressure again today and it was holding 1400 psi and it also wouldnt start at all for 3 times of 20 seconds of cranking once and set 2 map sensor codes in the process.
06-24-2007, 12:24 AM
#15
DTR's 'Go to Guy'
Sounds like it could be a poor connection at the Van Aken or something to do with the map sensor.. It also shouldn't read 1400 psi. Does the Van Aken hook up to the rail sensor too? Might be your problem!