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Rail pressure bouncing
Lately it takes longer for truck to turn over. No smoke, idles fine runs great. I noticed today that if I hold the fuel pedal down 1/4 the way the truck fires right up. At Idle when cold fuel rail pressure is bouncing from around 5.6 kpsi up 6.4 and as low as 4.4. When warm starts the same but rail pressure sits around 5.3 up to 5.6 down to 4.8 kpsi. Any ideas on this:confused013:. Thanks for the help.
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Please try searching next time there's tons of threads on this. Try taking you FCA. Fuel control actuator off and shaking it. If u can hear the check ball moving its good if no sound I'm willing to bet you FCA is toast. Its mounted on your cp3 pump with one electrical connection
First thank you for the help. I was thinking lp or fca. 2nd I have searched for days . Nothing with the same symptoms and didnt want to apply the wrong symptoms from some one else's post and possibly be sent in the wrong direction.. I learned the search first ask later when I first joined and caught crap for asking a question. Thank you again.
FCA would be the place to start with the bounce.
Could also be the RP sensor but they are expensive.
Might also be lift pump but that is not as likely if it starts good and runs good.
Could also be the RP sensor but they are expensive.
Might also be lift pump but that is not as likely if it starts good and runs good.
sorry didnt mean to come off as an a** lol but i would start there. Good luck on your findings.
@cerb it is taking about 3 or 4xs longer to start then use it did a couple months ago and seems to start a little better if I hold the pedal down 1/4 but idles and runs really good once started. the rail pressure today when I started it at idle jumped around from 5.8 up to 7.4 and down to 4.3 when cold then when warm mellowed out around 5.0kpsi +-.3.
@ matt No worries. I pulled the fca I cant hear the ball rattle but if I shake the crap out of it I hear a very light noise but cant tell if its the fca or my old wrist popping lmao. How obvious is the noise from the ball???
@ matt No worries. I pulled the fca I cant hear the ball rattle but if I shake the crap out of it I hear a very light noise but cant tell if its the fca or my old wrist popping lmao. How obvious is the noise from the ball???
Shaking the FCA to tell if is good is not a good test. They will rattle and still not work, not rattle and work, not rattle and not work. All that tells you is the little 3 sided check valve is moving, not if the solenoid is responding correctly to the PWM signal.
Holding down the throttle on these drive by wire trucks really does nothing for starting if the APPS is set correctly. The start circuit is preset and it will not fuel anymore than is needed to start. Once it gets a CPS signal over 200 rpms or so it goes into a different mode.
That said, if the APPS is dopping below preset values at rest or possibly shorting out it may cause it roll over more times until it goes to default mode. In a correctly functioning system depressing the throttle does not make it start faster or slower.
Since you have a manual the APPS is a lot harder to and more expensive to replace so before going that route exhaust several others. I would replace the FCA and make sure you have good fuel pressure to the CP-3, then, see if you can get a scanner to read APPS position from the ECU. The problem could be a bad battery, a bad cable connection, or a bad harness connection starting to show also.
The fans are a typical source of problems along with the AC clutch wire scuffing itself and throwing garbage into the system. Last but not least, injectors issues are still a potential problem area.
Holding down the throttle on these drive by wire trucks really does nothing for starting if the APPS is set correctly. The start circuit is preset and it will not fuel anymore than is needed to start. Once it gets a CPS signal over 200 rpms or so it goes into a different mode.
That said, if the APPS is dopping below preset values at rest or possibly shorting out it may cause it roll over more times until it goes to default mode. In a correctly functioning system depressing the throttle does not make it start faster or slower.
Since you have a manual the APPS is a lot harder to and more expensive to replace so before going that route exhaust several others. I would replace the FCA and make sure you have good fuel pressure to the CP-3, then, see if you can get a scanner to read APPS position from the ECU. The problem could be a bad battery, a bad cable connection, or a bad harness connection starting to show also.
The fans are a typical source of problems along with the AC clutch wire scuffing itself and throwing garbage into the system. Last but not least, injectors issues are still a potential problem area.
Thanks cerb. By pressure to cp3 you talking from lift pump correct? I re installed the fca and it has cooled off here so now the grid heater is kicking on . Still took long to turn over and while the grid heater was cycleling the frp bounced all over after it stopped cycling it sat at 5.0kpsi and would bounce up to 5.1 at idle. After I would rev it a little it would bounce around for a second when I let off then settle back at the 5.0 to .1. Would a bad prv cause the long cranking and is the test of pulling the banjo bolt out , drying out the bung and turning engine over if it fill with fuel a good test to go by?
PRV will cause a hard start and maybe some bouncing rail pressure.
Pull the banjo off the top and bag it or route it away from the PRV, it will have fuel coming back from the injectors out of it. Dry the PRV well out and to idle. If it gets wet ANY little bit it is bad. If it doesn't, unplug the FCA to max the rail pressure, if it leaks it is bad.
Pull the banjo off the top and bag it or route it away from the PRV, it will have fuel coming back from the injectors out of it. Dry the PRV well out and to idle. If it gets wet ANY little bit it is bad. If it doesn't, unplug the FCA to max the rail pressure, if it leaks it is bad.
PRV is bad filled with fuel immediately
That is going to cause some rail pressure issues if that is happening at an idle. Looks like replacement time. Check TCDiesel for a much more reasonably priced PRV.PRV is bad filled with fuel immediately
Would I be better off buying the prv from TC or the whole rail from genos?
While the whole rail gives u a pressure sender. And the relief valve IIRC. Little more money it is up to you. Personally I would just get the prvWould I be better off buying the prv from TC or the whole rail from genos?
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Thanks Rpadar
prv stands for pressure relief valve. if you get a spike in rail pressure, it opens to avoid damage. it can sometimes become worn out and lead to other issues as far as not maintaining and or making correct rail pressure.watt is the prv
No.watt is the prv
A watt is a measure of electrical energy transfer.
A PRV is is mechanical device to limit pressure.
They are not equal or comparable.
I really thought he meant "what" instead of "watt"No.
A watt is a measure of electrical energy transfer.
A PRV is is mechanical device to limit pressure.
They are not equal or comparable.
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