CRD fuel return test - Page 2 -
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post #16 of 17 Old 11-03-2019, 11:48 AM
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Thanks for posting an update! I had given up on mine but in rereading this thread, I got inspired again as we're experiencing the exact same thing. I feel like when one of us figures it out, it'll fix both of our Jeeps

I grabbed a fresh set of data during today's hard start. I wanted to get a good capture of engine RPM vs fuel rail pressure, but I forgot to enable actual data logging, leaving me with just graphs. Since I've got to wait a few hours for the engine to return to cold again, I'll post what I've got. It's probably not too helpful, but I figure if we'll get something useful between our sets of data.

I hadn't noticed until now, but the rail pressure was steady at ~6K PSI on the first start attempt, then ~4K PSI on subsequent starting attempts and when idling. It seems that 4K PSI is normal - I wonder if 6K PSI is over-pressured...

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post #17 of 17 Old 11-04-2019, 02:02 PM Thread Starter
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Location: Spokane
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If I recall correctly my key on engine off rail pressure hovers around 60psi. Engine cranking rail pressure around 300psi, and idling rail pressure just above 4000psi. I don't recall where I read it, but these pressures are about normal. Not sure if 6000 idling is too high but something to consider.

Mine hasn't yet timed out due to excessive cranking. It sometimes cranks for uncomfortably long though. There is a definite correlation to plugging in the block heater with almost perfect starts. That's what got me thinking about the glow plug system.

At the same time I feel like I also have an intermittent fuel pressure issue. After noticing the slight momentary drop in rail pressure just as the engine revs past 1100rpm I poked around some more. The momentary drop exactly coincides with an light squeak/rattle from somewhere in the rotating assembly at the front of the motor. The sound is like a dry shaft/bushing quiet until hitting 1100rpm. Makes me wonder if the gerotor in the high pressure fuel pump is worn. If I graph the rail pressure right after a cold start it drops about 300 to 400 psi for a split second as it revs up past 1100rpm with the corresponding noise up front and the slight engine stumble. Almost seems like I'm answering my own questions as I analyze my findings. However, I still want to hear from others who may be familiar.

All stock 08 GC Laredo CRD except for swirl motor resistor mod
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