Downhillnz wrote:I've played with the spring in the compensator.
Would having a lift pump to get the diesel to the pump without it having to vacuum it help?
I would say yes, pumping the fuel to the injector pump from the tank helps to keep air out of the fuel system, most fuel lines suck some air from the connections/filter fittings/priming plunger. The pump should be mounted as close to the tank as possible.
The injection advance mechanism inside the injection pump is activated by the dynamic fuel pressure . When running at full throttle the pump pressure can drop if sufficient fuel isn't always available at the pump inlet ( in addition to any entrained air bubbles), which can retard the injection timing a tad just when you need it the most.
The injection pumps fuel pressure regulator valve works against the interior pump pressure along with a coil spring (not atmospheric pressure), so if you pressurize the fuel pump supply the fuel pressure regulator valve gets tricked into supplying a higher pressure into the plunger feed orifice, and the higher fuel pressure will also advance the injection timing. Obviously any added on fuel pump should only operate when the engine is running in case of an accident. The o-ring seal on the throttle shaft (among other seals) can leak when the pump pressure is increased if the seals are past their use by date, luckily most of them are cheap to buy so some can be replaced by the confident home mechanic.
Have you rotated the diaphram in the boost compensator?