FUEL PUMP 6.9 DIESEL

check 12 volts reaches the fuel pump
relay or fuse
or replace fuel pump

pump pressure is too low
should be around the 22,000 psi mark needed to crack the injectors
indicates that the there is a fuel supply problem to the pump or pressure regulation from the pump

normally cause by air in the fuel pump. Check for fuel leaks on shafts.at filters, Check for proper tank ventilation. have the fuel pump checked for internal governor pressure.

White smoke for a diesel means air in the fuel system. You will have to start at the engine, I start at the line going to the fuel pump. Get some fuel in a can, remove the line to the supply side of the pump and put another line from the can to the pump. If it starts and doesn't smoke , then you have to work your way back to the tank and find the spot that is sucking air. If it doesn't start the I would replace the filter first, check again. There is a possibility that the injector pump is bad, but these don't usually throw white smoke. They just make the engine have very little power or no start.

Hi.

If fuel pressure is low and you have already replaced the fuel pump, then the problem is usually the fuel pressure regulator. The pressure regulator is in same assembly with fuel filter. The assembly is located to the fuel tank, bolted to the truck's frame. The pressure is tested connecting a gauge like this : Set Sealey VSE952 to the port on the fuel rail. The pressure on Grand Cherokee must be around 49 psi plus or minus 5 psi. If engine runs but pressure is below 44.2 psi , check for a blockage in fuel supply line between fuel rail and fuel pump module (e.g.kinked line). If the line is not blocked, replace fuel pressure regulator and filter. Test pressure with and without fuel cap on.

Another test to be done is reading pressure, then shutting the engine off with the gauge connected. If pressure goes down too quick, then the regulator is defective. After 5 minutes the pressure should not go below 24 psi. If it does replace the regulator.

If regulator is OK check for leaks at the injectors that can cause fuel pressure drops.To check for injectors leakage clamp off the rubber hose of the pressure gauge tool between fuel rail and the port. If pressure staysr above 24 psi and before was dropping, then a fuel injector or the fuel rail is leaking.

Below a diagram representing the fuel rail and test port. The engines from same years like your six cylinder have the port and rail in the same position.






Regards.

Ginko

SOUND LIKE IDLE SPEED TOO LOW HAVE IDLE SPEED CHECKED. REPLACE FUEL FILTER IF IT HAS BEEN A LONG WHILE A FAULTY TRANSFER PUMP OR FUEL INJECTION PUMP WILL CAUSE STALLING PROBLEMS

YOU HAVE AIR IN THE SUCTION LINE.OR YOUR ELECTRIC FUEL PUMP FUSE IS BLOWED OR PUMP IS FAULTY IF YOU CANT GET NO FUEL TO FLOW.

Gas or diesel having same problem, I'd start there to confirm fuel pressure . It may be pump running partially when cool, but when it heats up (the pump) it may be cutting out pressure wise. Not uncommon for a fuel pump to pump good when cold, then die once pump heats up from running. Still makes noise, but isn't supplying any or enough pressure.

tighten all fuel connections from filter to injector pump to injectors because if air is allowed in (between pressure pulses) then power loss will occur.