6.9 Fuel question
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Super Moderator
Joined: Jul 2004
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From: Ohio
6.9 Fuel question
Here we go.......
Guy I work with has a 6.9 and figures I know all Ford diesels.......
He replaced the injection pump, injectors and the truck runs the same as it did before. Okay....
So does the 6.9 have a lift pump in the tank? Is a valve between the engine mounted fuel pump and the injection available?
What PSI is needed for the fuel pump and injection pump, he says 40 and 90.
My advice was to get the facts, not replace parts. Everything he described seems to be starvation of fuel.
Guy I work with has a 6.9 and figures I know all Ford diesels.......
He replaced the injection pump, injectors and the truck runs the same as it did before. Okay....
So does the 6.9 have a lift pump in the tank? Is a valve between the engine mounted fuel pump and the injection available?
What PSI is needed for the fuel pump and injection pump, he says 40 and 90.
My advice was to get the facts, not replace parts. Everything he described seems to be starvation of fuel.
Posting Guru
Joined: Sep 2002
Posts: 1,897
Likes: 0
From: Northeastern Pa - USA
the 6.9l engine has, as original equipment, a lift pump just like a gas engine. It is mounted onthe right side of the engine and is driven off the cam shaft.
He may be suffering from a broken or cracked pickup tube in the tank. That pump will develope about 7 psi of pressure at the fuel filter (just ahead of the injection pump). He may also be suffering from air intrusion at the original water separator, mounted near the brake booster, from the water drain not seating properly. After those checks, he may want to check the fuel lines from the tanks, the selector valve, or fuel return system for air leaks. IF someone has installed an electric fuel pump, that may also be causing fuel delivery problems. There is my nickel.
He may be suffering from a broken or cracked pickup tube in the tank. That pump will develope about 7 psi of pressure at the fuel filter (just ahead of the injection pump). He may also be suffering from air intrusion at the original water separator, mounted near the brake booster, from the water drain not seating properly. After those checks, he may want to check the fuel lines from the tanks, the selector valve, or fuel return system for air leaks. IF someone has installed an electric fuel pump, that may also be causing fuel delivery problems. There is my nickel.
Posting Guru
Joined: Sep 2002
Posts: 1,897
Likes: 0
From: Northeastern Pa - USA
the 6.9l engine has, as original equipment, a lift pump just like a gas engine. It is mounted onthe right side of the engine and is driven off the cam shaft.
He may be suffering from a broken or cracked pickup tube in the tank. That pump will develope about 7 psi of pressure at the fuel filter (just ahead of the injection pump). He may also be suffering from air intrusion at the original water separator, mounted near the brake booster, from the water drain not seating properly. After those checks, he may want to check the fuel lines from the tanks, the selector valve, or fuel return system for air leaks. IF someone has installed an electric fuel pump, that may also be causing fuel delivery problems. OR a partially plugged fuel filter. There is my nickel.
He may be suffering from a broken or cracked pickup tube in the tank. That pump will develope about 7 psi of pressure at the fuel filter (just ahead of the injection pump). He may also be suffering from air intrusion at the original water separator, mounted near the brake booster, from the water drain not seating properly. After those checks, he may want to check the fuel lines from the tanks, the selector valve, or fuel return system for air leaks. IF someone has installed an electric fuel pump, that may also be causing fuel delivery problems. OR a partially plugged fuel filter. There is my nickel.
Thread Starter
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Super Moderator
Joined: Jul 2004
Posts: 21,113
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From: Ohio
Just what I figured.....wonder what book he was reading. Sooo I need to get some pressure readings and check a few things. He ought to really like the part of dropping the tank....
He may also be suffering from air intrusion at the original water separator
Whats the fix for this particular problem, we may have something here.
He may also be suffering from air intrusion at the original water separator
Whats the fix for this particular problem, we may have something here.
Post Fiend
Joined: Nov 2004
Posts: 5,638
Likes: 1
From: Manitoba
Water separator on the firewall fix ....shove a suitable bolt in the drain hose and it stops air intrusion.
Dont need fittings for fuel pressure test............
Do a pressure and flow test of the fuel pump at the Schrader valve on the filter header (FSS- fuel shutoff solenoid disconnected on IP). Remove the tire valve core and hook a hose and pressure guage on it should see 4-6 psi when cranking. Then do a fuel quantity test same place, should see 1/3 pint in 10 seconds of engine cranking, route fuel to a suitable container with a hose.
If there is a problem with the lift pump and you are changing it, ensure the new pump comes with instructions as to correct installation procedure if it is the newer model pump with the almost straight arm.
When was the filter last changed.........
Tell buddy to get a Haynes diesel engine repair manual and use it as a guide.
Dont need fittings for fuel pressure test............
Do a pressure and flow test of the fuel pump at the Schrader valve on the filter header (FSS- fuel shutoff solenoid disconnected on IP). Remove the tire valve core and hook a hose and pressure guage on it should see 4-6 psi when cranking. Then do a fuel quantity test same place, should see 1/3 pint in 10 seconds of engine cranking, route fuel to a suitable container with a hose.
If there is a problem with the lift pump and you are changing it, ensure the new pump comes with instructions as to correct installation procedure if it is the newer model pump with the almost straight arm.
When was the filter last changed.........
Tell buddy to get a Haynes diesel engine repair manual and use it as a guide.
Thread Starter
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Super Moderator
Joined: Jul 2004
Posts: 21,113
Likes: 3,939
From: Ohio
Gotta love FTE.....truck runs fine on a full tank of fuel. Pulling the tanks this weekend.....
Thanks for the info guys.
Thanks for the info guys.
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