no oil pressure!!!

I have a 1988 chevy r20 3/4 ton with a 350 5.7 & My oil pressure guage reads zero. I put a new factory guage in it & the same thing its still zero wont move. I replaced the sending unit behind the distributor and no help. is there any other oil pressure reading unit on this motor that Im missing. I know the guage is working cause when I installed it i put it on 60 psi manually and when I turned the key over it went straight to zero. could anyone please helpme with this..THANKS Neil

Have you checked your oil preasure with a manuall guage? Or just change from the factory electric guage to an aftermarket electric or mechanical guage.

Have you checked your oil preasure with a manuall guage? Or just change from the factory electric guage to an aftermarket electric or mechanical guage.
Actually I bought a new factory guage identical to the one that was in there hoping maybe the guage was the problem. I have not put a manual guage on it to test it. Could I pick one of those up at the auto parts store. and if so would I test it out of the same hole behind the distributor or is there an easier place. I didn't know if there was another place that the guage read on the block other than the one by the distributor. Let me know what you think and I really appreciate your help with this.. Neil

I have a 1988 chevy r20 3/4 ton with a 350 5.7 & My oil pressure guage reads zero. I put a new factory guage in it & the same thing its still zero wont move. I replaced the sending unit behind the distributor and no help. is there any other oil pressure reading unit on this motor that Im missing. I know the guage is working cause when I installed it i put it on 60 psi manually and when I turned the key over it went straight to zero. could anyone please helpme with this..THANKS Neil

if you truely had no oil pressue you would hear some rather bad sounds.about the only place you can connect a manual guage that I can think of off-hand is the access point near the distributor.

You need to get a manual guage on the truck to verify the issue. I would imagine that you may have extremely low oil pressure or there is some type of malfunction with the electrical setup?

IS the truck running ok ? buring oil? YOu hear any odd noises when the truck is running? If you suspect the truck has very low oil pressue then I would not run it except for just very breif periods to see if you can determine what the problem is. Your oild pump may be screwed or it may be a bearing issue.

I strongly advise you not to run your engine at all, unless your are checking your pressure. If you are still driving it stop, major engine damage will occure if your oil pump is not working properly.

I could be wrong here, but if the pressure sensor was actually registering zero, the fuel pump switch which is integrated into it, would not allow the fuel pump to run. This is a safeguard built into it to protect the engine in case of pump failure, or complete loss of oil pressure.

I could be wrong here, but if the pressure sensor was actually registering zero, the fuel pump switch which is integrated into it, would not allow the fuel pump to run. This is a safeguard built into it to protect the engine in case of pump failure, or complete loss of oil pressure.
The truck run fine and has no problems. The on;y time it smokes is when you first crank it up and I think this is the oil on the valve guides burning off. no really strang noises and it runs fine just curious what the deal may be. when I bought the new sensor from the auto parts store all they had for a 350 for that year was the one for a light. which is the ont that I changed out behind the distributor. theres no other unit or any thing for a guage on the motor.. thanks Neil

I don't know about a 3/4 ton model, but my '88 K1500's 350 (1/2 ton)has the oil pressure switch locate down close to the oil filter. It almost hangs upside down and looks sort of like a cone maybe 2.5 inches across. Mine went bad a few years back and started reading zero when the engine got to temp.

You want to change out the oil pressure sending unit that is next to the oil filter. The one that is behind the distributor is the oil pressure switch that deenergizes the fuel pump when oil pressure goes out

You want to change out the oil pressure sending unit that is next to the oil filter. The one that is behind the distributor is the oil pressure switch that deenergizes the fuel pump when oil pressure goes out
Hey I cahanged the one beside the oil filter and everything works great!!!!! THANKS to all that helped.. Neil

You want to change out the oil pressure sending unit that is next to the oil filter. The one that is behind the distributor is the oil pressure switch that deenergizes the fuel pump when oil pressure goes out

Thats true, I'd foregotten about that. I dont' think all 350's have the sending unit near the oil filter housing. Good call, though.