98 GMC hard start

I have a 1998 GMC two wheel drive pickup with the 4.3 L engine. Every morning when I first start the truck it starts right up fine. No hesitation. I drive about 2 miles to work, park it for 4 hours, and when i get on my lunch break the truck starts really hard. The spark plugs, wires, distributor and button have all been changed about 4 thousand miles ago and never really changed the problem any. The check engine light has been off and on a few times and every time I check it, the code has something to do with the system running lean and one of the O2 sensors shows no activity. Im not sure if this has anything to do with it but I think it probably does. I have no other explanation for it. Does anyone else have this same feeling?

What’s the exact code that is being logged?

Can you describe what you mean by “starting hard”? Does it take a really long time of cranking before it fires up, or is it spitting and sputtering at first, or something else?

when I say starting hard I mean it takes a lot of cranking time before it fires up. It can sometimes take 10 to 15 seconds before firing up. Another thing i noticed is that the oil pressure stays down to zero until just a couple of seconds before it starts. I can watch the gauge go up slowly to the normal range and then it will fire up. I think this is normal but not sure.

The problem might be with the fuel pump/oil pressure switch.

This is GM’s safety feature that turns the fuel pump off in the event of an accident. So for example, if the vehicle is rolled over the oil falls away from the oil pump pickup. No oil pressure, fuel pump shuts off. Or in a frontal collision that stalls the engine. No oil pressure, fuel pump shuts off.

So either the switch/sender is defective, or there’s actually low oil pressure when you go to start the engine.