oil pressure switch

[caden_cochran]

Hey what exactly does the oil pressure switch do on the 87 tbi 350’s. Im hearing that it goes to the computer some people says it controls the choke. What y’all think?

 

[Redfish]

There are two oil pressure measuring devices on the '87 TBI 350. The one under the engine, right above the oil filter is the sending unit for the pressure gauge. The second, smaller unit is located under and behind the distributor against the firewall. That one is a switch and is part of the fuel pump circuit.

Neither has anything to do with the choke.

 

[gmbellew]

oil pressure switch behind the distributor provides backup power if fuel pump relay fails as long as oil pressure is above a certain amount (3psi I think). that way the engine keeps running if the relay fails. and you can still start, but you will have extended crank time to build pressure.

some think it cuts power below a certain oil pressure as a safety mechanism, but that isn't true.

 

[caden_cochran]

Ah alright thank you. So basically neither could really affect how the motor runs unless the fuel pump relay fails?

 

[gmbellew]

Ah alright thank you. So basically neither could really affect how the motor runs unless the fuel pump relay fails?

unless you have a short to ground in the 440 (orange wire) circuit. that can cause all sorts of havoc. 440 feeds power to ECM, oil pressure switch, and fuel pump relay.

 

[caden_cochran]

you seem to know your away around these tbi’s this is off topic but whenever i crank it up it spits black smoke and misfires real bad almost sounds like i have a big cam. It goes away after a few seconds and runs normal with the exception of misfiring a little and running rich. Dude i’ve replaced just ab every sensor, injectors, everything to do with spark, throttle bodies pretty much rebuilt. it’s a lot to list but do u have any ideas?

 

[CorvairGeek]

unless you have a short to ground in the 440 (orange wire) circuit. that can cause all sorts of havoc. 440 feeds power to ECM, oil pressure switch, and fuel pump relay.

I had one do exactly that earlier in the year. This was a replacement for another (same brand - Warrantied) that leaked and always made the oil pressure light turn on until the engine lost pressure, AFTER the switch was turned off. This replacement did the same thing, until it left me stranded after blowing the fuse.
The new AC Delco works correctly, just like original one.
Aftermarket can't even make a simple oil pressure switch anymore!

 

[Rudy Mienert]

ok, slightly related,...how do I test the oil pressure gauge (91 cluster repinned into my 79 Blazer, LS swapped) ..new ACDelco sender, (I know it doesnt necessarily mean its good),...cluster sender wired directly to sender. Sender connected, stays at 0, unplugged, pins out above 80...HHEELLPP!!!

 

[mike]

Need help figuring out how to remove wire plug from old oil pressure switch 1987 k1o