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Old 06-14-2020, 10:24 PM   #1
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HEUI pump – internal resistance

With thanks to those that have posted thus far

To those with functioning HEUI pumps , those who undertake their own maintenance , those who are mechanically minded and those who just like to 'play'

As I continue to troubleshoot my warm starting issue –

it is looking increasing likely that the pump may well be the culprit, but I would like to learn 'why' –

others have suggested that the electrical coil inside the pump may be failing when hot

Caterpillar instructions when trouble shooting the HEUI pump is to observe the resistance of the solenoid within the pump WHEN COLD

A resistance of 8 ohms ± 2 ohms is considered acceptable

Caterpillar advise against checking the ohms readings whilst HOT as “a hot engine will show incorrect readings”


Finnings / Caterpillar are unable to assist, advising only to “check resistance when cold” !!

(With engine coolant temperature around 190 degrees F) - does anybody know what resistance a hot 'working' HEUI pump will display ??

(With all the usual legal liability 'not recommended', 'own risk', 'protective equipment', 'risk assessment' etc, etc stipulations )
when next in their engine bay, if easily accessible, would anybody like to 'put' a multimeter on their warm (operating temperature) pump, and post the resistance observed please ??

(My cold to hot resistance is a differential approaching 40% ?? - my reading / basic understanding of 'electrical resistance increase with temperature' suggests this is well outside normal / expected parameters ….......
but I do not know / cannot ascertain what is 'normal' for a hot functioning HEUI pump – hence my question

Thanks in anticipation for your continued assistance with this frustrating pursuit

Ian S.
2004 Cat C9 400bhp (9DG02935)
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Old 06-15-2020, 09:20 PM   #2
Cat
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Posts: 1,346
Red face

Quote:
Originally Posted by IanSmith-UK View Post
With thanks to those that have posted thus far

To those with functioning HEUI pumps , those who undertake their own maintenance , those who are mechanically minded and those who just like to 'play'

As I continue to troubleshoot my warm starting issue –

it is looking increasing likely that the pump may well be the culprit, but I would like to learn 'why' –

others have suggested that the electrical coil inside the pump may be failing when hot

Caterpillar instructions when trouble shooting the HEUI pump is to observe the resistance of the solenoid within the pump WHEN COLD

A resistance of 8 ohms ± 2 ohms is considered acceptable

Caterpillar advise against checking the ohms readings whilst HOT as “a hot engine will show incorrect readings”


Finnings / Caterpillar are unable to assist, advising only to “check resistance when cold” !!

(With engine coolant temperature around 190 degrees F) - does anybody know what resistance a hot 'working' HEUI pump will display ??

(With all the usual legal liability 'not recommended', 'own risk', 'protective equipment', 'risk assessment' etc, etc stipulations )
when next in their engine bay, if easily accessible, would anybody like to 'put' a multimeter on their warm (operating temperature) pump, and post the resistance observed please ??

(My cold to hot resistance is a differential approaching 40% ?? - my reading / basic understanding of 'electrical resistance increase with temperature' suggests this is well outside normal / expected parameters ….......
but I do not know / cannot ascertain what is 'normal' for a hot functioning HEUI pump – hence my question

Thanks in anticipation for your continued assistance with this frustrating pursuit

Ian S.
2004 Cat C9 400bhp (9DG02935)
No clue. But ECM will set a diagnostic code if outside of expected.
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Old 06-15-2020, 11:23 PM   #3
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HEUI pump - internal resistance

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Originally Posted by Cat View Post
No clue. But ECM will set a diagnostic code if outside of expected.
Cat,
This is the frustrating part -
we are not getting any codes - saves those we introduce when trouble shooting

Still trying to get into Finnings to get your PWM data

Be good, if you get an engine in and are able take a reading, for interest

Thanks
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Old 06-16-2020, 09:45 AM   #4
Cat
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They Finning needs to run a actuation pressure test. This a test in ET for testing the relation ship between Desired actuation pressure-actual actuation pressure, and the actuation solenoid current. This is a standard test for HEUI pressure problems.
The technician starts the test and manual raises the current going to the solenoid as they do this you should see the current change- Desired change then the actual pressure increase. This should happen every time the current is stepped up.
If you have the current at for example 30% and the Desired pressure is 2000psi but actual is lower than the 2000psi and the current starts stepping up by its self, this indicates a bad HEUI pump or a leak. In this scenario the ECM is increasing the current to obtain the desired pressure but there is a problem pump/leak so it cannot so it continues to increase the current trying to get the actual pressure up to the desired pressure. The Desired is a ECM generated expected number at a certain actuation current. I hope this helps.
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Old 06-16-2020, 08:39 PM   #5
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Ian,
Youtube PID function. This is what the system attempts to do.
SP (ECM Command setpoint)-PV (IAP Sensor process variable) (+,-) = error (+,-).
Cheers,
George
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Old 06-18-2020, 11:38 AM   #6
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Quote:
Originally Posted by Cat View Post
They Finning needs to run a actuation pressure test. This a test in ET for testing the relation ship between Desired actuation pressure-actual actuation pressure, and the actuation solenoid current. This is a standard test for HEUI pressure problems.
.................................................. The Desired is a ECM generated expected number at a certain actuation current. I hope this helps.

Finnings 'slot' now allocated for Tuesday next week

Will get suggested tests run - more later

Ian S.
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Old 06-28-2020, 12:48 AM   #7
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HEUI pump - internal resistance

All,

To close this thread

One of my CAT techs has been in touch with CAT technical

There is NO data on the resistance of the pump when warm - hence their instructions to check pump resistance when cold (for increased resistance due to additional metal on solenoid)

Thanks to those who contributed / offered to help

(The failure of the pump - prompting the question - has been tracked down to a temperature related failure of the electronics within the pump - understood to have been addressed when multiple improvements made to pumps (long after ours was manufactured) - a new pump and time will tell !! )

Ian S.
Exeter UK
2005 CC #31231
Cat C9 #9DG02935
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