Oil leak/ engine oil pressure indicator switch

[502Silverado]

I have an 87 R10 TBI 5.7L Silverado.  There is an oil leak at the top of the engine that has coated the back of the block on the driver's side.  I believe it is coming from what Summit Racing is calling an 'engine oil pressure indicator switch' which is in the brass fitting by the distributor.  I have an oil pressure gauge in the dash that starts low and then goes to zero.  I have no lights on the dash that light up indicating low oil or pressure.  I'm aware of the sending unit that is down by the oil filter and that will be replaced.  I've read that the switch is for either for a truck without a gauge and/or also used for a truck with a choke.  I'm aware that my truck does not have a choke.  Would a faulty switch be the cause of an oil leak at that location or should I be looking at the brass fitting it screws in to?  The switch and wire connected to the switch are covered/coated in oil.  Also, does anyone have a part number for the switch?  I would like to stay with AC Delco if possible but am open to other brands if need be.  Any help is appreciated.

[Chevygold]

If you originally had an automatic choke which has been removed, new carb or whatever then this switch can be simply removed and a plug fitted in its place it'll be either 1/8" NPT or 1/4" NPT, make sure the wires removed are made safe and ideally disconnect at the fusebox. Not sure about the sender for your gauge as mine has the old fashioned mechanical pressure gauge but shouldn't be too difficult to source.
I'm still a newbie on these trucks but I've just fitted an auutomatic choke so this bit is still fresh!
Graham

[MIKE S]

On that model the switch in back of the manifold is a fuel pump override switch in case of fuel pump relay failure. You will need to do a good cleaning in that area to determine what is actually leaking. Common points back there include the switch and fitting along with the distributor gasket and rear sealing area of the intake manifold were it meets the block. The large sending unit down by the filter is common to fail. If that doesn’t fix your pressure gauge problem the gauge itself is Very common for the resistor on the back to fail and best to replace the gauge itself. It is readily available from most of the common suppliers. I replaced my gauge with one 2 years ago and has worked just fine. For peace of mind I would temporarily install a manual gauge at the sender port and see what oil pressure actually is.
 

[502Silverado]

I appreciate the help.  The truck is all original as far as I know so I don't believe anything has been replaced or removed.  I'll check the other places mentioned for leaks.

[bd]

I agree with MIKE S. 

• The fuel pump oil pressure switch (OPS) next to the distributor is Standard Motor Products PS-262 (ACDelco/GM 10068563 is discontinued).
  
  
• The fuel pump OPS wiring connector pigtail is ACDelco PT1951.
  
  
• The instrument cluster gauge OPS (60 PSI) is ACDelco D8032 (GM 19244932).
  

If (when) changing the OPS next to the distributor be sure to support the elbow fitting that protrudes from the block using a proper size wrench.  The fitting is thin and can snap off with very little side pressure.  Use Permatex 57535 Seal+Lock Thread Compound on the fitting threads during reassembly.

[502Silverado]

Thanks, bd.  I found Standard Motor Products PS-221 off of a popular car parts website that says it will fit my vehicle.  I could be wrong but the PS-262 is showing that it doesn't fit.  I know the old one I removed looks different than the PS-262 and more like the 221.  I figure I can try both and see which one fits better.  I'm planning to replace the sender and the switch and spraying everything down with some brake cleaner or degreaser and go from there.  Thanks again for the help.

[bd]

Good catch.  The PS-262 that I posted is for a later application requiring three terminals.  However, I hesitate that the PT-221 that you found also is incorrect; used to control a dash oil pressure idiot light.  The descriptions of the various OPS's found using website search engines are ambiguous.  Look into the PS-221T and NAPA Echlin OP6671, as well.  Unless the OEM and aftermarket discontinued it, the fuel pump OPS shouldn't be this difficult to find.

[502Silverado]

What is the difference between the PS221 and the PS221T?

[Shifty]

What is the difference between the PS221 and the PS221T?

Premium and economy versions.  (T is the economy)

[bd]

Further research suggests that the OEM P/N of the fuel pump OPS was 25036938 (GM Parts Groups 1.800 and 3.910), which crosses directly to Standard PS-221/PS-221T as well as NAPA Echlin OP6671.  The difference between the two Standard part numbers appears to be company internal branding as Shifty stated.  The physical appearances of the PS-221(T) and OP6671 are correct, right down to the internal broaching for the keyed shape of the OEM connector and the number and positions of the terminal pins.

[Shifty]

Standard Motor Products owns Echlin (and Borg-Warner), FWIW.

[502Silverado]

Alright, I picked up the PS221 and PS269 (sending unit), changed the oil and filter and got everything installed and put back together.  I did notice that when putting the switch in that the brass fitting turned where it screwed into the block.  I tightened it slightly so it was snug and went to start the engine.  Engine started and no oil pressure.  I then realized that I didn't refill the truck with oil (only ran for about 15-20 seconds).  Shut off the truck, filled with oil and restarted.  Bingo!  My gauge is now working.  I didn't get a chance to clean all the gunk off the engine yet, I plan on doing that tomorrow.  I fully expect to have to fiddle with the brass fitting back by the distributor but hopefully I've fixed at least one of the leaks.  Thank you to all who responded and helped me out.  I hope I can do the same for you all sometime.

[Shifty]

Glad to see it going again....Oh, BTW, by not putting oil in first, you must have been "purging" the engine of contamination first. 

[502Silverado]

Absolutely!