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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

 

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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 by fjh
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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 by fjh
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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.

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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 by fjh
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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 by fjh
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