GM-GMC: Stalling, oil pressure switch, gmc diesel

Question
I have a 1998 GMC Diesel pickup. It has started stalling on me, sometimes it starts right up again and other times it won't start again for a couple of hours. We had a EGA Valve put in and it did not help, it still does the same thing.
               Albert

Answer
There are two main problem areas to check on.

One is the fuel supply to the injector pump.  GM uses an electric pump to transfer fuel from the tank to the injection pump.  The pump gets its power through a set of contacts in the oil pressure switch (OPS).  The switch cannot handle the current flowing to the pump and the contacts fail.  The transfer pump is also known to fail.  You should be able to hear or feel the pump running when the engine is on.  The pump is under the body an along the fuel line from the tank.

The second problem is the pump mounted driver (PMD) also called the fuel solenoid driver (FSD).  It is a black plastic housing, full of electronics, mounted on the passenger side of the injection pump.  It fails from getting too hot.  The cure is to buy another part and an extension cable to mount it away from the engine.

One other thing to check is the fuel filter.  It can cause the engine to stall if it is restricted or plugged.