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Oscilloscope testing HPOP

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My memory is hazy on this, bit I seem to recall being told that you can scope the HPOP pattern to see if it is failing. This is for a pump that still puts out enough pressure at times to allow engine to run. There should be a very regular pattern of peaks. If every third peak is missing, the pump is bad. The problem is, I can't seem to remember what sensor needs to be hooked to to get this pattern. Am I correct on this or is my fuzzy memory imagining this scenario? Posted Image

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You would read the ICP sensor... The graph on the IDS for ICPV is fast enough to show the peaks you are talking about...

 

On the old style barrel pumps, there are only two pumping chambers... So if every other peak is low or missing, then one chamber is failing or failed.

 

I thought there were only two chambers on the newer STC style pumps, too...

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The original 6.0L HPOP was a 7 piston swashplate style pump. In late 2004 the HPOP was changed to a V-4 style pump for the 2005 model year.Like Greg said, you would use the ICP voltage pid and make a recording. During playback you can fiddle with the view to examine the signal close up. I had one early style pump with a cracked rotating cylinder that had low ICP while cranking at operating temperature. The signal was quite clear... see attached screenshot.

 

Bad HPOP Screenshot

 

plungerbody-small

41-pooched-pump.jpg

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