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Fuel leak on 2008 duramax. Fuel is filling valley but bus starts, runs, has not lost power so I'm thinking return side. I can barely see the back of the pump from inside dog box, looks like wet around plug in back of pump, but thought if plug was leaking truck would show signs of loss of power, or no start. I have taken apart the whole front of motor down to pump and still see no return line leaking nor a sensor. Just wanted to know if anyone has come across this before and has an educated idea on a fix or idea on what could be leaking? 6.6l lmm

Posted by Anonymous on


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Posted on Jan 02, 2017

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SOURCE: 99 olds alero 2.4

I'm sure you have installed a fuel pressure gauge and monitored the fuel pressure while the problem is occurring?Another diagnostic tool which is easy to do,is while the problem is occurring,unplug one sensor at a time beginning with the Mass Air Flow first,.if it uses one.Many times,not always,depending on the sensor,if the sensor is taken out of the picture as far as what the PCM is seeing,like unplugging the MAF,the PCM will substitute the missing sensor output with a generic value that will allow the engine to at least run,and if unplugging for example the MAF,the engine idle speed returns to normal,you know you're onto the problem.You didn't mention if the engine ran ok other than the idle problem.As far as checking for vacuum leaks,i use something like brake cleaner or WD 40,more of a liquid,and it does sound like a vacuum leak.Plastic intake manifolds do develop nearly invisible cracks that open up more with heat.Revsisit the possibility.And as for the PCM,it is possible,but more likely a mechanical problem.Lastly,remove an O2 sensor or two before the catalytic convertor,run the engine and see if anything changes.Cheap way to verify the catalytic convertor is flowing and not restricting engine airflow,as i have seen bad cats cause misfire codes and strange problems.Good luck.

Posted on Dec 04, 2008


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