on mine, if i start cranking as soon as the light goes out, thats what i get, and my engine only has about 60k on the rebuild. however, if i wait 2-3 seconds after the light goes out, it lights off almost instantly.

 

i shall try that next time, i cranked as soon as light went off.

 

On my 1986, I give 8-10 seconds with Beru ZD1-A glow plugs (87 and up should be ZD9 glow plugs).

Firing all at once after two seconds of cranking sounds like a lack of heat at the glow plugs. 5 seconds is generally not quite enough for an ideal coldstart unless its very hot outside. But it also means you have good compression and injection.

What year is the truck? Is it 1987 and newer, or 1986 and older?

You may have some imperfect connections in the glow plug wiring that is eating up some of the current. The newer solid state (87 and up) glow plug controller uses closed loop risistance feedback in the circuit to time the glow plugs. Like most electric devices, glow plugs have higher resistance when they heat up.

So any extra resistance in the wiring from loose or damaged connections will fool the controller into thinking the glow plugs are hotter than they really are. This causes it to cut power sooner in order to keep from damaging them.

The 1986 and older system (WW2 vintage bimetal switch) should theoretically be capable of timing dynamically as well, but mine always gave 10 seconds or nothing at all.

Which is why I have a manual over ride switch in addition to the factory controller.

 

a little off topic, but would blowing the injectors out on an injector tester help em out? Or does the pintle and or nozzle simply wear out and cause improper fuel dispersion? i swear i got an injector knocking.

 

why would "blowing them out" on a tester do anything different than functioning on the truck. Think about it.

the discs sometimes leak internally, lower pressure, collapsed springs, carbon build up.

that's about all that can go wrong.