I have a 1996 Chevy C1500 5.0L Vortec V8. I lost oil pressure and found water in the oil. Replaced oil and filter so we could start the engine again. Regained oil pressure, no noise, ran smooth, no bubbles in coolant, no water/steam from exhaust. I think I've ruled out a head or head gasket problem. My theory is intake gasket leaking into lifter valley in to the oil pan. Looking for opinions.

https://www.gmtruckclub.com/threads/96-chevy-5-7-fuel-pressure-issue.1479391/

This thread has a few ideas on what to look for.

Question edited for a fraction more clarity, but 1996 is the year, 350 is the CC, and Vortec (after I Edited from 'vertic') is the engine buzz word for a dozen engines in the Ford range.

All questions on Fixya need 'year make model' as first 3 words.

The radiator cap is not relevant in this scenario, and also you mention 'sensor', the vehicle probably has 20!

The milky white mayonnaise is only visible after a run. After the engine cools, it separates back out. You need some professional diagnostic pressure testing, but on a 1996, it is probably going to be bad news.

Thats a tough one, the computer problems are huge on swapping the v8 in.. If it was me I would use an older motor that's not running a computer..or a crate motor ...

The 1990's chevy trucks(all of them) had fuel pump and grounding problems:

1. Check the fuel pump ground strap next to the gas tank as it could be broken from the connector or just loose.

2. Have a fuel pressure test done on the fuel lines at the engine top. (Note: if there isn't enough fuel pressure, replace the fuel pump.)

If the engine is turning over than none of the things you replaced will make the engine"start". You will need to check for fuel pressure and spark first.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

My Guess would be Pump bad...loosing line pressure when warm and fluid is thinner. possible sticky valve, I would try SEAFOAM TRANS TUNE in it, it frees up sticking vavles, Its great stuff and for $8.00 it's worth a try, otherwise..hate to say it but you might be looking at pulling trans and doing a pump change .

Could be the fuel pump is not providing the proper fuel pressure !
Fuel psi less than 50 psi no start GM CPI Vortec

Check for fuel presser bleed down, does the fuel presser hold after you shut it off? or does it fall off? if so check for bad pulsar valve or bad injector ect.

when carb is wide open ????? No carb ,fuel injection ???? Are the injectors being controlled by the PCM / ECM ??? Have replaced fuel pump, fuel filter and fuel pump relay.???? Did you test first ?

The freeze plug you replaced was due to rust or was it pushed out by freezing temperature? These plugs are not designed to protect the engine block from cracking during freezing temperatures, they are there to remove the sand from the block after casting it. I would drain your system completely and flush out the radiator thouroughly and fill with plain water, then run the engine and see if oil gets in the water, if it does and the plug was out due to freeze, then your block is probably cracked, although you could just have a head gasket leak. Oil pressure (40psi) is higher then water pressure (17psi), so getting oil in the water is always more prominent than the other way around. Flush out the system and let me know if oil returns to the water, hope this helps