I have a 305 TBI
I cannot locate the oil sending unit
Year is 1991
Been looking above oil filter but cant see it

Oil gauge is all over the place sometimes dropping to zero at idle
Engine never over heats so I am assuming its the sender
but
I cant find it
Please advise me

Thanks

Greg

 

it is literally screwed in right above the filter. its a few inches long, its like the only thing plugged into something other then the 02 sensor. its a really bug nut on it also.

 

If it's not directly above the oil filter, then it is located right next to the distributor on the driver's side of the back of the block.

Later,
Mike

 

no it cant be right next to the distributor cuz these tbi cars...especially 91...have electronic gauges. its gotta be above the filter. do u see a plug in a hole above the filter? if so then its definately near the filter. also, is there a little plug screwed in behind the intake manifoldnear the distributor? it should be a square shaped fitting. if so, its not near the distributor.

 

The 91 had them above the filter, its long and black... you'll see it.

Your car should have a screw where they're talking about by the distributor, but my friend's 88 T/A 305 TBI has it on the manifold, I didnt know what it was lol!

 

Actually you should have both. The one in the dist area is a sending unit, while the one above the oil filter is an oil pressure fuel cutoff unit. If your guage is all over the place its the unit behind the dist, if its just dead and sitting past 60psi then its more than likely the cutoff switch.

 

dude...our cars didnt have oil pressure cutoff switches. the sender switch is what tells u pressure... that is right above the filter. the one behind the distributor is for vacuum powered gauges i think... i dunno exactly...but on these cars the only 1 u have is right above the filter. i remember when i blew my piston rings and stuff...i was only running like 8 or 9 psi of oil ppressure... it was smoking like craz and was always in the red. this only lasted a couple days though then the motor went to **** so i replaced it. i wish i had a cutoff switch.

 

I have the same car and had the same problem. It's right above the filter like everybody is saying. However, it's been about 6 months since I replaced it and it's starting to leak again, giving me false readings. I say whatever......I know my pressure is fine, so screw it.

 

it probably leaked cuz ur not supposed to twist the barrel part of the switch when installing it. u gotta strictly stay on the nut part. of the black part twists and not the nut, its gonna leak

 

Yer right, CamaroGuy, we don't have a cut-off. We have more of a 'cut-on'... The oil pressure switch above the filter doesn't turn anything off, instead it turns on the fuel pump above a minimum oil pressure as a backup in case the fuel pump relay fails while you're driving (spinning motor + fuel cutoff = bad, fuel cutoff + traffic = worse).
However, should you want to set up a cutoff, just modify the harness at the fuel pump relay and set it up to run off a switch (not direct switched, just switching on the ECM's output lead). Flip it on before you start your car, flip it off once it's running, and you've got a functional cutoff, theoretically. I'll keep paying attention to my gauges, personally. If you'd like to prove to yourself that the oil pressure switch exists/works, go disconnect your fuel pump relay and start your car. It'll take a little bit longer than normal since the engine will have to build enough oil pressure while cranking to activate the fuel pump via the oil switch, but as long as your oil switch isn't faulty, it will start.. eventually.

 

i just had the same problem on my z71. no overheating, pressure gauge all over the place. my friend had check the oil just 3 weeks previous and no problems. i was 3 qts low on oil!!!!. i drove about 30 miles like this assuming it was the gauge.

thought i would share that. dont know where you sending unit is but it sounds like the other guys already told you that.

 

Yeah, that does force me to point out that you can also use the FP Oil pressure switch as a redundancy check to make sure it really isn't your oil pump by just yanking the fuel pump relay and driving around. If your car dies when your gauge zeros out, you've got a real problem. Tow it home. We also assume you HAVE checked you oil, right?