Join Date: Apr 2012
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sounds like an injector allowing combustion gases to backfeed through the fuel system.
copied from FTE:
COMBUSTION GAS ENTERING THE FUEL SYSTEM (Balloon Test):
Inert combustion gas(ie exhaust) in an injector can cause a random misfire in one or many cylinders. Combustion gas may leak past the injector's needle and seat, or the copper combustion seal. Once the combustion gas enters the fuel rail in the cylinder head, it then distributes to other injectors, typically on the same bank. To diagnose for combustion gas entering the fuel system:
1) Remove outlet fuel lines from the fuel filter housing on top of engine.
2) Install a balloon over each fuel line with a zip tie.
3) Disable the fuel pump and fuel injection control module (FICM) relays.
4) Crank engine and watch for compression pulses in the balloon.
5) For each line where compression pulses are evident, remove all but one (1) of the glow plugs from the affected cylinder head(s).
6) Crank engine and watch again for compression pulses.
7) Remove the glow plug and transfer it to the next cylinder in the head and repeat Step 6.
8) For each cylinder where compression pulses are evident remove injector(s) and inspect copper gasket and lower O-ring, replace if necessary. If gasket(s) and O-ring(s) are OK replace injector(s).
the richest ones are not those who have the most, but those who need the least