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    Renault Clio 1.5 DCi K9K 2002 - Hard start when hot - Fixed # Archived Message

    Posted by Dave Hill on September 10, 2009, 9:44 pm

    This one is a frustrating one to crack. After doing the rounds before arriving at my place (with only three days to fix it apparently ) I have a very intermittent hard start fault on a Clio (year 2002) 1.5 Dci (Delphi System). This will start perfectly from cold & only struggles after it has been switched off for a few minutes when hot. The idle is a little erratic too & it hunts slightly. Other than that, once it is running, it is faultless. It occasionally logs the following DTC when it struggles to start....

    DF137 (2DEF) Rail pressure regulation function = > maximum limit.

    I have scoped this to death & I am struggling to capture it when it falters. I have also run it on an independent fuel supply & eliminated any air ingress or fuel quality issues. The one thing that stands out to me when studying the following waveform, is that the rail pressure signal, from the moment of cranking rises very sharply (actually its instant). Instead of the usual smooth increase from zero pressure.




    In this capture I am concentrating specifically on the rail pressure sensor. Scoping the feed, signal & ground....



    I am confused by the increase in the 5 volt sensor feed at this point. ???

    In the next capture, I am performing the Max Pressure test, with all injectors & the Inlet Metering Valve unplugged. Remember that the Inlet Metering Valve defaults to a full flow/pressure state when unplugged (de-energised)



    After studying things, I decided a replacement Inlet Metering Valve was not an unreasonable suggestion, & sure enough, the "hunting" or surging at idle has gone. Unfortunately the hard start fault has re occurred though (in the car park & away from Pico ). I have swapped the Injection relay for a known good one too.

    I am sure I have missed a few things out, as it has been a funny week.

    Thanks for looking (HELP! )

    Dave

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