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Not sure '91?? my issue is that I have near zero oil pressure and the fuel pump don't run.....I had the intake off and just dumped the oil down the valve train, forgetting to fill the damn filter, I would think cranking it a bit without firing up would fill the filter very quickly....NO??
Well it may take a few seconds but not long, I agree.
The oil pressure sender on the L98s is at the back of the block, near left rear corner of the intake-manifold-to-head junction. Photo here.
Notice in this picture there are two units; one is a sender for the oil pressure gauge and the other is the oil pressure switch that works as a backup to the fuel pump relay. When you said "oil pressure switch that will kill the fuel pump if oil pressure is lost" - it's actually the reverse of that. That oil pressure switch will keep the fuel pump running if the engine has oil pressure and the fuel pump relay has failed. It's essentially a backup for the fuel pump relay.
The reason I ask your year is because these switches / senders changed somewhat over the years. Your car may have one combined switch / sender like mine (late production '89) or it may have two separate switch / sender units like this picture, which is supposedly from a 1991 engine. Check your situation to be sure.
It is the reverse of what you say, the switch keeps you running, it is a backup for the FP relay.
The sender, right beside it, sends pressure information to the dash.
If you have FP issues, apply 12V to the ALDL connector terminal "G" and see if the pump runs. Also check the fuse. If it doesn't run then, its the pump or the wiring AT the pump, either or both can fail.
OK, wiring diagram sez there is an oil pressure switch that will kill the fuel pump if oil pressure is lost.....what is the location for the switch???
The wiring diagram says no such thing. This is one of the many falsehoods about the C4 that simply refuse to die. Mainly because people insist on claiming it is so.
Arbee is right. I used to think the same as OP because of an old (wrong) online article which I read years ago and it stuck with me.
But when Arbee pointed out the error I went into the FSM wiring charts and verified that he's exactly right. The Oil Pressure Switch is a backup for the FP relay.
oil pressure switch
