Problems with 94 s10 blazer not starting

I have a 94 s10 blazer (4.3 W engine, 4 door, 4WD) not starting all the time. The fuel pump does not always kick on by itself, I'm using a wire and the #13 pin on the data link connector to start it when it doesn't kick on. I already replaced the relay, and that didn't do any good. I don't know if there is a connection bad under the dash since someone before had tried to install an alarm and failed, but nothing *looks* wrong.

I basically have three things happen when I go to start it:

It starts up without any intervention
I use a wire to start it, and can remove the wire
I use a wire, and I have to leave it in, otherwise it dies

Now, I seem to have power to the relay, even when it won't start, could the oil pressure switch be flaky enough to cause this problem, or is this possibly something worse? From what I understand the oil pressure switch is also what controls the oil pressure gauge on the dash. I don't think it hardly moves at all, even when it is shut off, is this correct?

If you have any more questions, I'll be glad to respond, I just don't want to have to use a wire to start it (I am already enough of a redneck as it is!)

I was wrong about using the G pin to start it - My friend was helping me, and I thought he had run the wire from the G pin wire to start it, but it is actually from the wire running back to the fuel pump itself. ( I just was looking at the wire coming from under the dash and assumed it was from the pin)

I got the wiring diagram, and checked all of the wiring to the relay, which all checks out, I have power to it constantly for the power, and I have ground, I also have power coming in for 2 seconds from the computer when the key is turned on, and power going out for 2 seconds when the key is turned on.

I have continuity (minus a little resistance) from the relay out to the pump feed, but I never get any power to the pump feed (That has me stumped!)

I am rather curious why I am not getting anything at the data connector. I don't even have continuity there to the pump line, which I thought I should.

I also noticed under the hood, right behind the trans fill was a wire that has a single flat female plug that has continuity to the relay out. On the wiring diagram, the only things that should have continuity are the relay out are the fuel pump, the fuel pump in on the pcm, fuel pump prime connection, and the oil pressure switch. Should there be a connecter that it is hooked up to that would cause a problem?

Are there any fusible links in line that would cause a problem?

Sorry if I am confusing you, I have about a hundred different trains of thought right now (including it mysteriously catching on fire).

Marker wrote: