Ok fellas I've done everything I can think of to get fuel pressure on my d4. New gaskets on filter housing plates. Tried bleeding it several times.  Pulled a large plug next to the fuel inlet tube on the bottom. It only had a long spring in there. Filter housing is full but no pressure coming out. Any ideas what I can look for or check? 

In theory the fuel flows from the tank to the transfer pump which gives the pressure to the filter housing. Could be a faulty gauge or the transfer pump is shot. Do you have your manuals yet?
If you changed fuel filters and bled the system the problem is probably the transfer pump. Usually Not to tough to fix. If you crank the engine and don't get spurts out of the opened vent at the top of the fuel tower, probably no pressure from a faulty transfer pump. If you get fuel spurting out it is a faulty gauge.

Hi,
scan below shows the bypass or relief valve and spring on a D4 but the D2 is virtually the same.
Early valves were hard plastic and tend wear grouves across their seats and sometimes rust or grouved housing faces can cause leaks and low pressure, later valves are alloy with a rubber face.
The light springs collapse in time and a gentle stretch works wonders--the coils can also weaken due to rusting from water laden fuel.
Fuel blockages between the tank tap and the transfer pump are a factor too. Dirt and rust can build up at the transfer pump inlet and low points in the supply tube from the tank.
Rust flakes and foreign objects can clog the tank outlet before the tank tap also.

Normal fuel pressure on these is around 15 to 20 psi. see below.
FYI. at the Dealer we did a test on the Part Numbered gauge as described to establish the gauge graduations vs. pressure readings.
Cheers,
Eddie B.

Have a service mans which does t even go into injection. Just found and ordered a parts manual. I'm not real sure the check valve is in place under the spring.  Pulled it and nothing came out with the spring.  May have to mirror in there and see what there is. Either a hole or valve. I must have a fairly early machine serial 7J102. Finding only one manual available for sale going that low. 

there is a seperate book for the main engine i assume there is for all of them. i have a book for the d315.

So I did find a metal plunger deal in the relief plug. Tapped on the housing with a hammer and it finally dropped out. There was no rubber or plastic on the end of it.
I’m assuming the transfer pump is the 2 gears behind a plate on the bottom end of the filter housing ?

Hey Neil yes it seems to be. It has to be compressed to start threading the plug in. Here are some pics of what I'm working with.