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 Post subject: Crank no start when warm
PostPosted: Sat Jan 21, 2023 6:26 pm 
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Hi all,
I got an 05 kj 2.8 crd about 7 months ago as a cheap run about/farm hack. Was not expecting much from it as it's cheap old rusty got 260,000 ish Km done but it's not actually too bad to drive. My biggest complaint would be how badly it tow's a heavy trailer.
It has always been slow to start takes a while to prime but has never failed to start from cold, just recently some times it will not restart after a short journey. IE you jump in from cold get it going drive 3-4 miles switch off and it will crank but not start, left sitting for 3-4 hours it will start, once running from cold it will keep going until turned off. Usually no codes 1 or 2 times I have had P0093 but it is rare, live data is telling me low fuel rail pressure while cranking anywhere from a couple of hundred to 700 psi. My fuel rail pressure sensor was wet seemed to be leaking diesel so I have swapped that for a higher rated Bosch that didn't solve the problem.
Next I loosened the feed from the high pressure pump to the rail to make sure I had fuel that far, I had fuel there.
Next move was to pull the return hose off that back of the rail to see if the pressure regulator solenoid was closing, now what seems wrong to me I have diesel, a good flow coming out of the end of the fuel rail while the rail pressure is low.
Who knows for sure if the regulator is controlled by the rail pressure sensor and ECU only IE no other sensor inputs?
Sould there be any flow out the rail bypass at low pressure and cranking rpm?
I have read in the wsm that if you take the pressure regulator out of the rail it must be renewed true or false? I am assuming something crushes/deforms to form a seal wsm doesn't go into detail, my thought being it's a whole secondhand rail or a new regulator.
Many thanks in advance.
James.


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 Post subject: Re: Crank no start when warm
PostPosted: Sat Jan 21, 2023 8:45 pm 
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This list will give you some items to get started on checking out or ruling out!

Some items that can cause a no start condition:
    1. **Air in fuel**, leak on suction supply to CP3, stopped up fuel filter, etc...(Inadequate fuel supply to CP3 will prevent injection pump from supplying proper fuel pressure to fuel rail)
    2. Weak battery, low voltage. (voltage level dropping below minimum required voltage for ECM to function properly. ~8 volts or less at ECM)
    3. Crankshaft Position Sensor faulty (loss of signal) (If no CPS signal is present, the ECM will not allow engine to start/run)
    4. Camshaft Position Sensor faulty (loss of signal)
    5. Fuel Quantity Solenoid (on back of CP3) The Fuel Control Actuator solenoid valve is a pulse-width modulated valve that controls the amount of fuel sent or delayed to the high-pressure pump elements inside the high-pressure pump.
    6. Cascade/Overflow Valve (on top of CP3) Regulates lubrication to internal parts of the injection pump and regulates the fuel pressure to the fuel quantity solenoid valve on the back of CP3 injection pump. Also, controls the amount of fuel being returned to the fuel tank via the fuel return line.
    7. Fuel Pressure Solenoid (on end of fuel rail) aka: Fuel Rail Pressure Control Valve (The fuel pressure solenoid controls and maintains the rail pressure constant along with a control current provided by the engine control module (ECM))
    8. Fuel Rail Pressure Sensor (on side of fuel rail)
    9. Fuel Injector (leaking by not allowing fuel rail pressure to build up to required operating pressure)
**No. 1 cause of a No Start Condition!

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 Post subject: Re: Crank no start when warm
PostPosted: Sat Jan 21, 2023 10:11 pm 
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Thanks for the reply W W Diesel. I reckon I have ruled a fair bit of that list out but I am open to suggestions.
Air in fuel, it would have been running fine seconds before the fail to start/low rail pressure.
Battery low, only after loads of cranking still won't start on a boost till it decides it's ready.
CPS, I am showing rpm on live data.
5&6 Valves on HP pump, doubt it as I am getting fuel up to the rail seconds before and during the fail to start.
Fuel pressure solenoid possibly yes that's why I posted the question, I am not 100% sure what controls it or how it should behave I find it strange that it is dumping fuel while the rail needs more pressure
Rail pressure sensor is new
Injectors I will pull the returns off and check tomorrow.


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 Post subject: Re: Crank no start when warm
PostPosted: Mon Jan 23, 2023 1:28 pm 
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Fordelocks wrote:
Thanks for the reply W W Diesel. I reckon I have ruled a fair bit of that list out but I am open to suggestions.
Air in fuel, it would have been running fine seconds before the fail to start/low rail pressure.
Battery low, only after loads of cranking still won't start on a boost till it decides it's ready.
CPS, I am showing rpm on live data.
5&6 Valves on HP pump, doubt it as I am getting fuel up to the rail seconds before and during the fail to start.
Fuel pressure solenoid possibly yes that's why I posted the question, I am not 100% sure what controls it or how it should behave I find it strange that it is dumping fuel while the rail needs more pressure
Rail pressure sensor is new
Injectors I will pull the returns off and check tomorrow.

There should be almost no fuel dumping out of the Fuel Pressure Regulator on the end of the fuel rail during engine startup.
Maybe these descriptive and diagnostic documents can be of help for your understanding of the Fuel Pressure Regulator operation?
I have included a document for the Cascade Overflow Valve and Fuel Quantity Solenoid Operation also.

Fuel-Pressure-Solenoid-on-End-of-Fuel-Rail
Image

Quote:
Cascade Overflow Valve and Fuel Quantity Solenoid Operation

OPERATION
The COV has a spring-loaded center spool-piece that has a drilled channel with three passages: one for initial low-pressure lubrication, one for lubrication at housing-pressure , and one for overflow. The valve is operated in three stages based on the level of pressure at the inlet.

Stage 1
When the fuel pressure entering the tip of the COV is between 0 and 3 bar (43psi), pressure is too low to overcome regulator spring tension and fuel flows through the center channel, only . This passage always allows fuel flow through to the pump center-ring and lubricates the pump bearings and internal moving parts. This circuit also allows air to bleed during initial cranking and returns the air to the fuel tank.
The COV is in Stage 1 during cranking, only.

Stage 2
When the fuel entering the COV exceeds 5bar (73psi), but is less than 12.4bar (180psi), the spool-piece moves against spring tension aligning a second passage for lubrication purposes.
Stage 2 can be reached during cranking and initial start up.

Stage 3
When fuel pressure exceeds 12.4bar (180psi), the spool-piece aligns with the overflow passage. This stage relieves the pressure into an overflow circuit that sends the fuel back to the inlet side of the gearotor pump, thus limiting maximum fuel pressure to 12.4bar (180psi).
Lubrication fuel continues to flow through all channeled passages during this stage.
Excess fuel is sent back to the fuel tank through the fuel-return circuit
Stage 3 is reached at over-pressure

FUEL QUANTITY SOLENOID
AKA FUEL CONTROL ACTUATOR

DESCRIPTION
The Fuel Quantity Solenoid valve is located on the back of the front cover of the high-pressure pump. The solenoid is pulse-width modulated by the ECM and meters the amount of fuel that flows into the high-pressure elements inside the high-pressure pump.
The solenoid is inactive up to 30 seconds after Ignition switch is initially keyed to ON position to allow maximum fuel pressure to the fuel rail during cranking and start up. ECM assumes FQS valve control when CPS signal and rail pressure are within acceptable limits

OPERATION
The Fuel Quantity Solenoid valve is a pulse-width modulated valve that controls the amount of fuel sent or delayed to the high-pressure pump elements inside the high-pressure pump. The ECM determines the fuel pressure set point based on engine sensor and rail-pressure inputs. If the actual fuel-rail pressure is too low, the ECM commands the solenoid to allow more fuel to flow to the high-pressure pump. This minimizes the difference between the actual fuel-rail pressure reading and the set point. The ECM will also operate the solenoid to delay fuel, reducing flow-rate, if the fuel-rail pressure becomes too high.
The FQS valve is commanded open by the ECM to allow the high-pressure pump to build maximum pressure (1600bar, 23,206psia), or closed to decrease pressure.
Thus, rail fuel-pressure can be increased or decreased independent of engine speed

The valve also has a fuel tank heat-protection function* that meters the exact amount of low-pressure fuel to the high-pressure pump to prevent excessive injector-heated fuel from returning to the fuel tank.
Temperature of fuel from the fuel tank is measured at the fuel inlet in fuel manager head via a temperature probe in the inlet side of the fuel-heater module.


Fuel System Diagnostic Flow Chart
Image

_________________
Supporting Vendor and Moderator of LOST
05 Jeep Liberty CRD Limited :JEEPIN:
Ironman Springs/Bilstein/Shocks
Yeti StgIV Hot Tune
Week's BatteryTray
No FCV/EGR
Samcos/ProVent
SunCoast/Transgo
Carter Intank-pmp
2mic.Sec.Fuel Filter
Flowmaster/NO CAT
V6Airbox/noVH
GM11 Bld.fan/HDClutch
IronrockArms/wwdieselMount

98 Dodge Cummins 24 Valve


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 Post subject: Re: Crank no start when warm
PostPosted: Mon Jan 23, 2023 2:45 pm 
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Joined: Sat Jan 21, 2023 5:10 pm
Posts: 5
Thanks for the info, I have I think, determined by sticking a wet finger in the air that I have enough diesel spilling off the rail to actually run the Jeep. I fired the parts cannon today and ordered a new solenoid valve ( only €221.40 ) and should have that fitted tomorrow night, I will post the results.


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