Help with 1st start of AZZ/pump problems

[81 vw pu]

When I converted my 81 caddy from gas to diesel, I removed the complete fuel pump assembly from the truck, and ran my fuel lines straight from the tank to the filter I mounted on the shock tower.
Had to make an adapter to connect the supply line to the tank as they are different size. Never did see a check valve, unless they are in the gas fuel pump assembly. I prime my injection pump by removing the hose on the outlet banjo fitting on the injection pump and hook up a handheld vacumn pump with a short length of clear hose, pump till fuel appears in clear line, install return line and start.

[fatmobile]

 No check valve on the MK1,
 the MK2s had the water seperators underneath, the check valved worked with that.

 Good to hear it runs when bottle fed,.. but can't drive around like that.
 I don't know the history on this truck's fuel tank.
 Did it sit for a long time with gasoline in it. Dried-up gas will leave a buch of screen-clogging crap in the tank.

 When you pressureise the filler hole, you are pressurising the fuel leaving the pump too. Shoving fuel into the pump from both ends.
 It's not like feeding the pump.

 Good to hear you can pull fuel through the filter, from the tank, by sucking on the filter output,
 It's usually a good indicator of how hard the fuel is to pull from the tank.
 But sometimes you can't suck much before there is fuel at your mouth.
 A clear fuel line before the filter will help you see if air is coming from the tank, or the filter.

 A primer bulb before the pump would help prime the pump, shove air all the way out the top of the pump and back to the tank.

[Toby]

Your problem is an air leak between tank and pump. Most likely at the pump end of things. Banjo fittings have to be absolutely clean or they may leak when a piece of grit gets under the washer. The fuel filter could be loose, missing its gasket, or the gasket could be out of its groove. If its got a drain on the filter, make sure that it is closed tightly. I had one with a pin hole in it, once. It did not leak because it always had a vacuum on it when the car was running and the fuel drained back into the tank when you shut it off. If the bubble  forms at the pump and quickly it has to be close to the pump, I suspect. If the banjo fittings have ever been off of the plastic line, that will cause an air leak. Safety wire will usually cure that however.

[regcheeseman]

Had exactly this fault on a caddy 2 weeks ago.

It ran fine with the NA engine fitted but with a TD in it had exactly this fault.

We knew it was a supply problem but took a while to find.

In the end, the supply line from filter to pump was at fault

It had a black rubber section at each end and a clear section in the middle where you could see air, the factory crimp connection between black and clear pipe was allowing a lot of air to be pulled and little diesel.

[Digital K]

solved w/ mk2 fuel filter.