327Chevy

Hey guys,

I've got my 327 sitting in the car now, but am still hooking up the wiring, hoses, etc. I am trying to use all the stock sensors, wiring harness etc from the 88 Camaro 305 TBI motor.

It appears that there are two oil pressure sensors/switches for the 305 TBI engine. One is at the top of the block near the distributor hole. This has a one wire connection and I think it is for the gage on the dash (not 100% sure). The other is on the side of the block just above the oil filter and has a 2 wire connection. I believe this one goes to the computer (not sure). The thread sizes are different between the two ports (@ dist vs. @ oil filter).

The problem is that 327 block only has the port @ the distributor. So I can hook up the sensor that I think goes to the gage here. The threads fit and this would be just like on the 305. But the 327 has no port @ the oil filter area. What happens if I just don't install that oil pressure switch from the 305?

I guess the two easy options are to leave the connector that would have gone to the oil switch @ the filter disconnected or to jumper it's terminals closed. How unhappy would these easy options make my computer?

I have done some reading on thirdgen but it seems that these sensors & switches are used differently on TPI vs TBI. I need to know specifically for TBI.

Anybody been through this?

RFmaster

'327

Single pole sensor is either gauge or an oil pressure switch used for dash idiot light.
TBI system uses a combination three connector sensor/switch. A switch portion closes once oil pressure exceeds 6 PSI - this is used as a safety back-up for FP relay (contacts) are in parallel with FP relay. The sensor portion is used to drive instrument cluster oil pressure gauge. Put T - I sourced my from HD for less than $5. Photo is a bit out of focus, sorry:









BTW, all SBC have oil pressure galley tap(usually pluged) just above oil filter flange. It's usually plugged and plugs are difficult to remove (I tried, it is not for the weak of heart)!



Good luck

//RF

RFmaster

ECM cycles FP relay during POST test. Having oil pressure bypassed with short will keep FP always on when ignition is in RUN/START. This will cause FP error code to be set as ECM is looking for FP relay cycle.

/?RF

327Chevy

Thanks, RF.

I may end up with a tee like you used. But space back there in the firewall /distributor area is tight.

ALSO my sensors look different, see attached. The can shaped one is what I think drives the gage and was located @ the distributor. It has one terminal. The other one from the oil filter area is longer and narrower and has two terminals.

Any idea why you've got 3 terminals and I've got 2?

It sounds like I can temporarily jumper the 2 connections @ the filter connector and run the car but I will get an error code - but no expected damage. Do I understand this correctly?

I borrowed these images from the websites for the chain parts stores. Credit to Autozone & Advanced.

Thanks again.

Apeiron

You won't get a code at all. If you have a working ECM, you don't want to jumper the 2 connections.

Damon

You don't want to jumper those 2 connections (that provide the alternate fuel pump power feed). It's BATTERY HOT. Found that out when priming the oil system on a new engine. As soon as oil pressure came up the fuel pump kicked on and started spilling out the end of an unconnected fuel line- and the key wasn't even in the ignition!

I notice the picture of the sensor you posted above DOES HAVE 3 TERMINALS. But you're saying your electrical connector only has only 2. Wondering if someone clipped off the 3rd wire and ran it up to that second oil pressure sensor on top of the intake. I don't recall my 92 RS having any oil pressure sender up by the distributor- jsut 3 wires to the one down by the oil filter.

di11avou

iTrader: (1)

Your sensors are set up the same as my car. One by the distributor for the oil pressure gauge and a switch by the oil filter for backup power to the fuel pump.

You shouldn't have any problems leaving the switch by the oil filter disconnected. As the others have said, you do not want to jump them together.

327Chevy

Thanks guys.

OK sounds like the plan is to leave the oil pressure switch that was at the filter off of the car. Insulate the connector with electrical tape & tuck it out of the way.

Right?

So my fuel pump will still feed the engine and everything right?

Hard to believe GM would have bothered to include that sensor if it doesn't have any impact on whether the engine runs and if omiting it doesn't set a code...I guess stranger things have happened.

1ADan

iTrader: (4)

doesn't this sensor also kill the fuel pump if the oil pressure drops to unsafe levels? I thought I heard this rumor before?

RFmaster

NO, the FP relay contacts are in parallel with oil pressure switch. The oil pressure switch acts as a backup to FP relay. If relay fails, you can still have FP (engine) running provided that oil pressure is above 6PSI.

//RF

1ADan

iTrader: (4)

my apologies, I miss-read your previous post.

327Chevy

I can confirm that a 1988 TBI camaro will run without the oil pressure switch connected.

I just started my 327 for the first time & broke in the flat tappet cam.

Sinfulrelations

Not to Jack this thread but my oil pressure switch is above the oil filter on my 92 rs 305, can I move it up by the distributor with no adverse affects, because I can't seem to get my new one in the old location.

Damon

With the proper fittings, yes, you can. The port above the oil filter and the one up on the "China wall" near the distributor are connected to the same galley inside the block. They recieve the same amount of oil pressure (main oil galley, after the filter).

Sinfulrelations

Sweet!!! Thanks a lot!!!