cov Posted May 27, 2016 Share Posted May 27, 2016 i have an 06 Mack and i was wondering why i have lost all fuel prime. i put a gauge on it and it doesn't move. whenever you try to start the truck it will not start. but if i prime the pump while someone else is turning the key i may get lucky and it may fire up. as soon as you shut it down, you cannot start it back up. my real question is. do i have to pull the front of the engine to replace this pump? also which lines move the fuel from the tank to the fuel rail and which move fuel back to the tanks Quote Link to comment https://www.bigmacktrucks.com/topic/45400-fuel-pump/ Share on other sites More sharing options...
fjh Posted May 27, 2016 Share Posted May 27, 2016 (edited) Is this A Grey engine? Model of truck will help too! The fuel pump is bolted on from the back side of the front cover on a grey engine with 2 13 mm / 1/2 inch headed bolts! the big line to the pump is the suction line make sure you got no leaks on this line IE: racor type filter with a plastic bowl on the bottom! also the fitting in the middle of the block just above the compressor is a check valve it may be malfunctioning ITS cheaper than a pump if your going to grasp at straws start at these items first! Edited May 27, 2016 by fjh Quote Link to comment https://www.bigmacktrucks.com/topic/45400-fuel-pump/#findComment-334690 Share on other sites More sharing options...
cov Posted May 27, 2016 Author Share Posted May 27, 2016 yes sir it is the grey engine. chn613. the line that goes above the compressor is dryrotted. is that my suction line if so i believe i should start with that correct? Quote Link to comment https://www.bigmacktrucks.com/topic/45400-fuel-pump/#findComment-334693 Share on other sites More sharing options...
fjh Posted May 27, 2016 Share Posted May 27, 2016 (edited) That is the return line ! The fitting at the block is a check valve that first! If the line is not leaking its not an issue for this problem If you look closely at the Green filter (If Mack) on the front of the engine theer is a number -8 or 10 line that will be the line to chase down for suction leaks If that is the one you put your gauge on that is why you saw no preasure cause there is none ! the preasure should run at or between 60 to 100 psi on the preasure side Edited May 27, 2016 by fjh Quote Link to comment https://www.bigmacktrucks.com/topic/45400-fuel-pump/#findComment-334694 Share on other sites More sharing options...
cov Posted May 27, 2016 Author Share Posted May 27, 2016 the line on the front of the engine is where i put my gauge and it never moved. i removed the return line and primed my hand pump and check valve had pressure on it. so i know i need to replace the return line. Quote Link to comment https://www.bigmacktrucks.com/topic/45400-fuel-pump/#findComment-334695 Share on other sites More sharing options...
fjh Posted May 27, 2016 Share Posted May 27, 2016 (edited) But is that check valve holding? the return line it may need replacing But will not be the cause of your issue , your either sucking air via a line or primary filter or the pump seal! restricted fuel line on the primary side ! Edited May 27, 2016 by fjh Quote Link to comment https://www.bigmacktrucks.com/topic/45400-fuel-pump/#findComment-334696 Share on other sites More sharing options...
fjh Posted May 27, 2016 Share Posted May 27, 2016 (edited) Any big restriction on the primary side could cause the pump to suck are around the pump seal! However the pump failing is not out of the question they do fail but they aint cheap! Edited May 27, 2016 by fjh Quote Link to comment https://www.bigmacktrucks.com/topic/45400-fuel-pump/#findComment-334697 Share on other sites More sharing options...
cov Posted May 27, 2016 Author Share Posted May 27, 2016 no sir the check valve is allowing fuel to slowly bleed down out of the valve. i will check the primary side now. Quote Link to comment https://www.bigmacktrucks.com/topic/45400-fuel-pump/#findComment-334699 Share on other sites More sharing options...
cov Posted May 27, 2016 Author Share Posted May 27, 2016 i found no restrictions. except for that check valve being bad. what all do i need to take off to get the old pump off? Quote Link to comment https://www.bigmacktrucks.com/topic/45400-fuel-pump/#findComment-334700 Share on other sites More sharing options...
fjh Posted May 28, 2016 Share Posted May 28, 2016 The filter two lines two bolts! Quote Link to comment https://www.bigmacktrucks.com/topic/45400-fuel-pump/#findComment-334768 Share on other sites More sharing options...
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