It has been brought to my attention that there is a condition with the OPS relay mod I posted that can cause ECMB fuse to blow when cranking because of a backfeed to the glow plugs.

To remedy this here is a new diagram showing the factory relay and the mod relay with a diode installed to stop this condition.

Without the diode you could have a no start caused by the previous mod if installed as posted originally.

 

Note: this is for 95 and older trucks with electric lift pump.
example of a useable but overkill diode:
http://www.ebay.com/itm/GE-20-Amp-50-Volt-Stud-Mounted-Diode-Wind-and-Solar-Blocking-Diode-50V-20A-/271277867361?pt=LH_DefaultDomain_0&hash=item3f296bc161