D4 7U Fuel Injector????

You are on to it!

If you still have no gauge pressure look at the fuel bypass valve on the bottom of the fuel filter housing where the fuel line comes in. Should be held on with 2 bolts and if you remove the bolts, fuel from the tank should flow out in a good stream if the tank valve is still open. there's a spring in there that can rust away and break, and a button on top of it that can get crud on it and prevent it building good pressure. fortunately it will still run well if that is the only reason for the low gauge pressure. In other words there's plenty of fuel available, it just isn't at the normal pressure. If the filters are stopped up, the pressure is low, AND there's a shortage of fuel delivered so performance suffers.

NZ, pick up a calibrated gauge of not more than 40 lbs. & hook it temporary into the system even where the gauge is now & see what pressure you have. The original gauges only have run position etc. so with the calibrated gauge you should get maybe 15 lbs. idle & maybe as much as 25 lbs. more or less at high idle when things are normal with the system. CC gave you some useful info. to follow too.

Doug you are right on with the way you do a bleed job & filter change so if all would follow this procedure it will work out best.

I agree with your basic idea, except filling the housing with fuel. It should be filled from the fuel tank of the tractor, hopefully filled before trying to bleed the system. Not a good idea to pour fuel out of a can into the fuel filter housing or in later models into the fuel filter itself. We can do it, but we take a chance of introducing small buggers into the system past the filters. I used to precharge filter housings, but I don't anymore. Pony motor will turn the main engine enough to build pressure in the fuel filter housing. Bleed air off the top at the bleed screw then work your way along the injector lines at the injectors. As mentioned, it helps a lot if the fuel tank is full. Our Cat pre cup engines start much easier with a mix of Power Service in the fuel. In cold weather the main engine will start with 20 seconds of preheat with Power Service, it takes more than 3 minutes without PS and the engine misses and smokes white. This is around 15 degrees F.

Dave if you fill the filter base before hand the fuel anyway has to go through the elements before it goes to the pump housing so the danger of getting unfiltered fuel to the system is about "O" so I can,t see where there is any worry about dirt getting in unless the cover etc. is not cleaned up before it,s put back together.We always did it this way at the dealer & the many years I did engines & others there too never saw one engine that ever caused a problem if it was done in a proper clean manner.

If the tractor has been sitting for this long, check to see if you have algae growing in your fuel from moisture. My 7U had some get started before I bought. I treated it to kill it and a glob of black snot plugged the fuel line coming from the tank to the transfer pump. It took a while to find that. Good luck.

You are on to it!

If you still have no gauge pressure look at the fuel bypass valve on the bottom of the fuel filter housing where the fuel line comes in. Should be held on with 2 bolts and if you remove the bolts, fuel from the tank should flow out in a good stream if the tank valve is still open. there's a spring in there that can rust away and break, and a button on top of it that can get crud on it and prevent it building good pressure. fortunately it will still run well if that is the only reason for the low gauge pressure. In other words there's plenty of fuel available, it just isn't at the normal pressure. If the filters are stopped up, the pressure is low, AND there's a shortage of fuel delivered so performance suffers.