Ask a Heavy Equipment Repair Mechanic for Answers ASAP
Does your repair shop have Cummins Insite or another electronic tool to monitor the engine parameters.
I think you may have a pressure sensor "stuck in range". This means that the sensor is giving out a valid pressure signal, however it is incorrect.
The other thing that may have happened is a connector or wiring problem giving a bad reading.
When you disconnect the sensor, the engine goes into a default setting and ignores the inputs from the sensors.
I would want to monitor the inlet manifold pressure and temperature, fuel pressure and fuel pressure setpoint and fuel temperature and see if they change.
You could try disconnecting the inlet manifold pressure and temp sensors, one at a time.
The other thing to check is the delivery pressure from the pump, measured at the fitting on the side of the CAPS pump, this should be 150 PSI
Hope this helps
Hi trucks 113,
3 PSI of gear pump pressure is way too low, should be 150 PSI.
Check for a fuel restriction, lift pump has a valve behind it that opens under vacuum, once the lift pump stops running after 45 seconds, this may be sticking.
There is a relief valve in the gear pump, however very unlikely for this to fail in two pumps, like you say something on the chassis.
Check fuel tank breather and all pipework and fittings.
OK, let me know how you get on
checked fuel pressure at the pump with mechanical gauge, strong 160psi. printed out at idle monitered parameters accel interlock switch-locked
accumulator pressure 3779.3
accum pressure sensor voltage 1.3v
accum press setpoint 2000
ambient air pressure 28.9
battery voltage 13.8
calibration software phase 070402e5
clutch switch released
coolant temp sensor voltage 2.2
cps state valid sync
cruise set/resume switch neutral
cruise/pto switch on
diagnostic switch on
engine brake switch level 0%
engine harness supply voltage 0.50v
engine oil pressure 70.6
engine oil pressure signal voltage 3.2v
engine speed 726
engine speed sensor supply voltage 5.0v
engine torque limit switch off
fan clutch status on
fuel economy 0.000mpg
fuel pressure deviation 90.8 psi
fuel temp 69.7
gear ratio 16.0
idle increment switch none
injection control valve circuit status fault
injector control valvedelay time 2.648ms
injector control valve open time0.058ms
intake air heater #1 off
intake heater#2 off
intake man pressure 0.8inhg
intake man pressure sensor signal voltage 0.5v
intake man temp 67.6
intake manifold temp signal voltage 3.5v
j1939 engine control source none
j1939 engine control status inactive
j1939 retarder control source none
j1939 retarder control status inactive
key offs 6943
key switch on
manual fan switch on
max expected vca 27.8 deg
oem harness supply voltage 5.0v
percent fuel 0.00%
percent throttle 0%
powertrain protection torque limit 0ft*lb
pto additional switch off
pto set/resume switch neutral
pto status inactive
rear axle ratio switch low
remote pto switch off
service brake switch released
throttle signal voltage 0.5v
throttle signal (idle validation) on idle
throttle supply voltage 4.2v
total ecmtime (key on time) 16987:39:56 hh:mm:ss
transmission gear ratio 16.00
user fueling state low speed gov state
vca 32.4 deg
vehicle speed 0
water in fuel no
Two things stands out, accumulator pressure is 3779PSI, when accumulator pressure setpoint is 2000PSI,the maximum expected VCA, (valve close angle, how long your pumping control valves remain closed to produce the required fuel pressure) is 27.8 degrees, however your actual VCA is 32 degrees.
you would need to see a datalog to know if this was an issue, although it fits in with your problem.
Was a complete CAPS pump fitted, or was it a modular repair?
Was the engine surging when this snapshot was taken?
Engine speed is 726RPM, yet user fueling state is low speed governer, what is your normal idle speed?
Are you able to get a datalog done and post it here for me to check?
Has the workshop carried out the CAPS pump tests, the main one I am thinking of is the pumping control valve cutout test to ensure both pumping elements are functioning correctly.
Just checking, are the symptoms the same as before the pump was changed
One thing you mention, a noticeable difference from all actuating testing performed,
when doing the pumping control valve test, you should not have a noticeable difference, there will be a dip when changing from both to one, what you are looking for is the VCA, there should not be more than 13 degrees difference from front to rear.
Does the engine still surge when the tests are being carried out.
There is a J1939 cutout test, has this been tried to isolate the dashboard and ABS commands.
The first thing I would do was to run the engine from a container of clean fuel, straight into the gear pump inlet on the side of the pump, also the return back into the bucket, that will tell you if it is a pump/sensor issue or a fuel supply/return issue, the length of pipe used will need to be prefilled with fuel.
OK thanks, XXXXX XXXXX keep on about it, just making sure in my own mind.
If you can get a datalog of the engine and fuel pump sensors as well would be good, a couple of minutes of surging would be enough.