RIP CM2250, 2013, 800,000km 20,000 hrs
05-14-2022, (Subject: RIP CM2250, 2013, 800,000km 20,000 hrs ) 
Post: #73
RE: RIP CM2250, 2013, 800,000km 20,000 hrs
(05-14-2022 )Hermjeji Wrote:  
(05-06-2022 )Rawze Wrote:  maybe monitor the commanded vs measured pressures and see if there are pressure spikes?.

See the test below, It looks like once it reaches peak command, it does spike up and down. The last spike was at key off. This is just at 700 idle with the leakdown test. It's obvious it fails the leakdown test. However, on the other 3 ISX's i have not seen this when doing the leakdown test, it fluctuates, but not this much. Even the old rail leakdown tests, they stayed at 28500-29000 psi, not jumping up to 30k and down like this.



I want to hook up to it when it's loaded and pulling to see how it data logs then (but that won't be till Tuesday/Wednesday).

So far, it does not look that unusual besides failing a leak test. It is normal for the pressure to fluctuate about 200~ish bar or so. The fuel system pressure regulation works like any other hydraulic bypass-charging system, so the up/down fluctuations are normal within that range. 300 bar (if memory serves me right), maybe is max before setting off alarms.

Just for FYI purposes:
- Unlike a low pressure hydraulic system with a spring regulator...,. a hydraulic bypass-charging pressure regulation works by closing a valve so that the pump can make/build up the pressure. Once the pressure is reached, then the valve opens again, putting the pump into 'neutral' .. not allowing it to supply anything until the pressure has fallen off again by a certain amount. .,. then the valve shuts again to top it off whenever it is needed only. - this makes the pressure go up and down constantly by a few % as the fluid gets consumed, does work, etc. and the valve opens and closes due to pressure drops.

It is the equivalent of a truck going down the road and the driver shifting it in and out of gear, back into neutral once it gets up to speed... and then going back into gear after it slows down a bit, so that the average speed can be kept up ... unlike one that may have the the cruise control set and remaining in gear all the time, keeping a very steady speed,,. always in gear, wearing things out.


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