round 2 no fuel pressure on 1997 chevy truck again

After replacing oil preasure switch and having success with starting a running strong for the last week no start today. Back to no fuel pressure again. This time trouble shooting truck will not even start by bypassing the fuel relay contacts to keep fuel pump running. Switched out supposed faulty oil pressure switch with no luck. Oddly plugging new OPS trying to start truck pump was still running after turning ignition off. I could pull on plug to stop pump press to make it go again but cant repeat the situation. Bad plug?
At a lost again. Truck was not driven for a day.

the only way the pump could of kept running after key off is if the contacts in the relay are welded together or the wires are shorted to power somewhere.
most likely place is on the exhaust manifold on the passenger side near the rear of the cylinder head,start checking there to make sure the loom hasnt fell onto the manifold.

if that is okay,turn your ignition switch to on,look at your PRNDSL display on the dash,is the little shift indicator line lit up??
if not,the ignition switch is bad.
if it has been failing for a while you may have noticed that occasionally it wont shift out of first gear.

another place those years of trucks are known for wiring problems is under the truck in the wiring harness especially where clamps hold it next to the frame.
let us know what you find,that is an odd one with the pump staying on after key off.

Say, looks like I might have unpluged something else near the oil pressure plug but I can’t find a plugin for this 3wire flat plug.

Ignition is all good the shift indicator light is good the spark from a grounded spark plug hooked to a plug wire is strong.

I was able to press on the side of the plug for oil pressure switch to get fuel pump to operate again. jiggled wires to create same thing but nothing. Something to do with plug or switch. Tomorrow I’ll put old switch in to see if it does the same thing. Also no wires seeming to be hitting mannifold look closer where goes through sheild protector by manifold. Had cut hole in floor to easily access trany bolt in that corner where shield is when I put new tranny in last year.
Something not letting fuel into the spider. I can’t imagine the new fuel pressure regulator went bad. All vacuum lines are hooked up and look good
Thanks for the help with troubleshooting

that three wire plug doesnt happen to plug into the module coming out of the distributor does it??
if so,that is the trigger wires to the injector circuit but I dont remember it being a flat plug in.
if you are able to pinch the oil pressure switch connector together and make the pump run,that connector is coming apart on the inside,time for a new pigtail if thats the case.

check your plug in at the injector spider,they were notorious for the terminals opening up and losing connection there as well as breaking wires at the individual connectors that serve each poppet.

power is common to all injectors,they are triggered on the ground side.
this wouldnt keep your pump from running or running constantly but would explain why you dont have fuel to the injectors when it does run,that is barring the distributor being unplugged.

keep after it,I know you will find it !

I had the same problem with the same year truck. The wiring for the fuel pump runs along the driver side frame. On my truck the wiring was not protected and rubbed on the frame and shorted out intermittently. Very frustrating for a time. This also can cause it to not shut off. Follow the wiring along the frame rail where it goes thru a hole and see if it shorting.

Still fighting the old beast. Now I burned up a starter because cylinder 7 has an injector stuck open cuasing hydrlock. Checked #7 control lead coming out of pcmm to see if pcm grounded out inside causing injector to stay on but no indecation of that or wire grounding out in harness. Today I’ll take plentum off again and inspect spider wires for grounding issues.turn key on fuel poors in #7 right away. Changed oil easy 2 quarts of gas in with oil, I didnt think it was going to stop draining.

I will also switch #7 injector with another injector to see its still is open from a different outlet.

Man I sure am learning out a lot on how these vehicles operate.
From one spectrum to the other, no fuel pressure to to much causing hydrolock.

Ever thought about taking it to a good shop?

Never occurred to me that was an option.