Marcb,

Since you just changed the engine, make sure all the fuel line connections are tight.

It unlikely that the injection timing would change so rapicly unless the timing chain jumped. You might pull the valve cover and check the cam timing. If the chain jumped, the reading on the balancer on the crankshaft will be way off the TDC mark when cam timing marks are aligned .

This is one time that I would tell you to check the fuel filters. Too bad the 603 engine (NOT MOTOR) doesn't have a manual fuel pump because this pump makes checking the filters much easier.
Take off the fuel line from the secondary fuel pump to the injection pump, crank the engine with the starter and see if any furl comes out. If no fuel comes out, its filters, fuel pump, or a hole or loose connection in the fuel line that is letting in air. There is also a fuel strainer in the fuel tank thet could be plugged.

P E H