rayrancho Posted June 13, 2018 Share Posted June 13, 2018 I have a fleet of concrete trucks. A driver complained of harsh vibrations in truck and further diagnosis showed that said truck idles at 500 rpm, while the others are at 625-650 rpm smoothly. When idled up to 625-650 truck is smooth. Where to look? Driver states truck does not run poorly or have any other symptoms when driving other than slightly sluggish on take off... if low fuel pressure was the cause, wouldnt the computer pick up the issue and make necessary adjustments to put idle at desired range? idle does not fluctuate with a/c on or off...I haven't found any information on fuel pressure specifications from fuel pump. I appreciate any help/ leads. I do not have a scan tool for this truck. Quote Link to comment https://www.bigmacktrucks.com/topic/53563-06-mack-granite-cv713-idle-issue/ Share on other sites More sharing options...
RobM626 Posted June 13, 2018 Share Posted June 13, 2018 47 minutes ago, rayrancho said: I have a fleet of concrete trucks. A driver complained of harsh vibrations in truck and further diagnosis showed that said truck idles at 500 rpm, while the others are at 625-650 rpm smoothly. When idled up to 625-650 truck is smooth. Where to look? Driver states truck does not run poorly or have any other symptoms when driving other than slightly sluggish on take off... if low fuel pressure was the cause, wouldnt the computer pick up the issue and make necessary adjustments to put idle at desired range? idle does not fluctuate with a/c on or off...I haven't found any information on fuel pressure specifications from fuel pump. I appreciate any help/ leads. I do not have a scan tool for this truck. Auto or manual? Quote Link to comment https://www.bigmacktrucks.com/topic/53563-06-mack-granite-cv713-idle-issue/#findComment-400480 Share on other sites More sharing options...
rayrancho Posted June 13, 2018 Author Share Posted June 13, 2018 manual Quote Link to comment https://www.bigmacktrucks.com/topic/53563-06-mack-granite-cv713-idle-issue/#findComment-400481 Share on other sites More sharing options...
RobM626 Posted June 13, 2018 Share Posted June 13, 2018 Turn cruise control on/off 3 times quickly . Set the rpm you want then press the clutch pedal to set new rpm Quote Link to comment https://www.bigmacktrucks.com/topic/53563-06-mack-granite-cv713-idle-issue/#findComment-400482 Share on other sites More sharing options...
RobM626 Posted June 13, 2018 Share Posted June 13, 2018 If you have an electronic fault I don’t think it will work so clear the faults if you have the lamp lit Quote Link to comment https://www.bigmacktrucks.com/topic/53563-06-mack-granite-cv713-idle-issue/#findComment-400483 Share on other sites More sharing options...
rayrancho Posted June 13, 2018 Author Share Posted June 13, 2018 ill try this and let you know the outcome. thanks for the tip. Quote Link to comment https://www.bigmacktrucks.com/topic/53563-06-mack-granite-cv713-idle-issue/#findComment-400488 Share on other sites More sharing options...
solog1977 Posted June 28, 2018 Share Posted June 28, 2018 After you press the on/off switch 3 times, do you set the idle speed via pedal or the accel/dec switch followed by pressing clutch? Quote Link to comment https://www.bigmacktrucks.com/topic/53563-06-mack-granite-cv713-idle-issue/#findComment-401484 Share on other sites More sharing options...
fjh Posted June 28, 2018 Share Posted June 28, 2018 with set resume the switches! Quote Link to comment https://www.bigmacktrucks.com/topic/53563-06-mack-granite-cv713-idle-issue/#findComment-401492 Share on other sites More sharing options...
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