Isuzu Repair: Isuzu repair, fuel pressure gauge, isuzu pickup

Question
It's a 1992 Isuzu Pickup with fuel injection with low low miles

Often its hard to start. It turns over but does not make any attempt to fire. At
the initial turn of the
key it starts and runs like a champ or just turns over and makes no attempt to
fire. It seems that
with the initial turn of the key it runs or does not fire.

Usually it's a starting problem but now it stops while your diving and then is
hard to start. There's
only a 50/50 chance your going to make it where your going without
stopping.

I'm driving the truck and the engine goes dead. I noticed the the tachometer
drops to zero right
away even though the engine is still turning. I popped the clutch just to see
what would happen
and the tach did not move even though the engine speed increased as I was
coasting. Not sure
what this tells me except that it's not fuel because if the fuel injectors had
stopped working I
think you should still have spark and the distributor is still turning sending a
signal to the tach.

I hooked up a fuel pressure gauge and a timing light which I can see from the
drivers seat. When
you turn it over and it doesn't start, the timing light does not light indicating
no spark or maybe
not enough spark. After you try a few times and the engine does fire up the
light goes on right
away.

I noticed today that if you just turn the key to "on" without the engine turning
the timing light will
pulse erratically. Also, in the "on" position the tach pulses a bit even though
the engine is not
turning. How can this be.

In addition to this when you turn the key to "on" the fuel pump is supposed to
come on and then
shut off after a few seconds when it sees that the engine is not turning. This
is a safety feature.
I've tested this several times and the fuel pressure does not come up when
you turn the key to on,
only when the motor is turning.

Any thoughts? 

Answer
Well Isuzu's are known for rearing their ugly electrical problems Chris. The buzzing of the fuel pump is actually the fuel pump priming solenoid sending fuel from the tank to the engine.  I would check the voltage of your fuel pump from the tank at the two/three connections to the engine. Have yuo had your main wiring harness ground checked? A loose ground somehwere can cause al kinds of fun problems. Any thoughts let me know okay??