D7F dozer 3306 low fuel pressure

I've had the lines get blocked with debris (rocks, sticks, rust, GUNK) one in the pickup tube in the tank. mostly at tight bends and at connections..
Good luck

There is a screen as part of the shut off valve/line assembly at the tank. Did you check that?
Is the tank vent (part of the cap) clear?

Thanks for the replies. I’m pretty comfortable there is no more rubbish in any of the housing, lines etc.I cleaned them then compressed air through everything. I wondered about a dirty fuel tank cap. So while I was doing all this I took the cap off. I haven’t cleaned any screen at the tank fuel tap no. Makes sense there is one there... might look at it next. What I did do was run the main large fuel line from tank to primary filter into a bucket and checked flow. Running a full line and lots of it. With no engine running the gravity head pressure is quite good. It will push a stream of fuel out of the fuel pressure gauge port.

On the sleeve metering pump there is a bypass valve under the cover (lower bottom RH) that keeps the pressure of the feed in the housing at a maximum of 25-32 psi. Fuel which goes through the bypass valve mixes with the fuel flow from the tank and back to the transfer pump and into the housing. Check to see if this valve is functioning and not held open by trash or malfunction.

Hi, Thank you. I’ve looked at the pump prior everywhere I could. I had read in the manual that my transfer pump didn’t have a check valve and the main pump did. When I had everything off bar the main pump I couldn’t see anywhere this valve could be. Do you have a picture of where this plate is please? Thanks

#4 is the fuel pressure relief valve
#3 is the transfer pump check valve.
 [attachment=65251]Transfer pump check valve and Pressure Relief valve.jpg[/attachment]
 

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Hi RAEME,
you have what is known as a Compact pump on your D7F engine.
I would now check the fuel flow from your tank to the primary fuel filter to rule out any blockage in the tank tap screen if fitted, and the fuel supply lines and fittings down to your primary filter.
If you indeed have a good supply flow by gravity then maybe it is your gauge that is faulty.
The specification for the fuel pressure is in the region of 25 PSI to 32 PSI at high idle.
Cheers,
Eddie B.