Oil Pressure Sending Unit--TBI V-8 dash gauge

[Schurkey]

The oil pressure sending unit that supplies signal for the 0--60 psi gauge on the dashboard of the TBI-era V-8 engines is a known "common-failure" part.

I had a spraying-oil type of failure which put the final nail in the coffin of my sending unit, which has been reading considerably higher pressure than it had any right to for a couple of years now. (The previous sending unit was replaced because it indicated too-low oil pressure)

My usual supplier is NAPA; and the sending unit which had just failed was a NAPA purchase back in about 2003 or so. When I tried to buy another replacement oil sending unit at NAPA, I discovered that the part they're currently selling does not fit my '88 K1500 5.7L. The diameter of the sending unit is so huge that the heat-shield has to be forced into place; but even worse is that the sender hits the engine block before it can be screwed-into the pipe-and-80-degree elbow arrangement that GM provides.

The original sender and heat-shield on left, and the too-large sender and NAPA part-numbered box on right:


Original sender and OEM eighty-degree pipe/elbow on left, too-large sender and 90-degree elbow/pipe that I tried to make work. (Failure--if it's far enough out from the block, it runs into the exhaust.)


Far as I can tell, NAPA (p/n OP6649) and O'Reiley's both catalog the wrong part number, and they don't fit. CarQuest catalogs a different part number (p/n 57013), and those fit reasonably well. I returned the NAPA sending unit, and installed the CarQuest sending unit.

(Edited: See post #3 for current part numbers)

[thzpcs]

I actually found an OE supply for them here. I haven't personally used one from them as I haven't had the oil pressure sending unit fail. Yet... But, I've ordered plenty of stuff from them and they've done a great job so far.

[Schurkey]

Three-and-a-half years later, and my sending unit failed...again.

These things are pure junk. Yesterday it indicated "zero" oil pressure when restarted after mailing a package at the Post Office. No lifter clatter, no rod knock...I drove it 10 or 15 miles to get the thing home.

I went to NAPA, Advance, and O'Reillys on the way home. None of them even show a part number for the sending unit on their computer. They list the wiring connectors, and the oil pressure switch that drives the fuel pump, but not the sending unit for the gauge. It's as if whoever compiles the list of parts to display on "the computer" forgot about that application. Very strange. The guy at Advance went to the paper catalog, found Advance # S6649, but this is the big gold/copper colored one that doesn't actually fit. It's made by BWD--or at least it is packaged in a BWD box.

So I pull the connector off the top of the sending unit, and the gauge goes to the high end of the scale. Gauge works. I rip the sender off the engine, connect an OTC pressure gauge...and I have my typical 50 psi. CONFIRMED: Not an oil pressure problem at all--it's a sending unit problem.

Doing some more on-line research, BWD S4320 seems to be the correct one. It has a silver case, and green paint around the end with the electrical connector.

http://weblink.carquest.com/acl/?mfg...rtNumber=S4320

The NAPA / Echlin crossover from that number is OP6729. AutoZone sells it as PS150. Autozone is by far the most expensive, at $36. The other brands are less than $21.

NAPA warranty is 3 years, 36K miles.
Advance says "Limited Lifetime warranty"
O'Reillys warranty is "Limited Lifetime"
AutoZone warranty is "Limited Lifetime"

Advance took over the local CarQuest, we'll see if they'll honor the warranty on the failed sending unit.

None of these stores locally actually stock the part, so I won't have one to verify and install for a few days.

[j cAT]

get one from scrap yard .. OEM .. these are china crap.

[TiVoPrince]

Rats I already bought the RockAuto Advantech branded 4G7. It is labled to substitute to PS150, S4049, PS-269 and 1S6577. Good on me its a 3Y-36K warranty. Good on me that it matches the silver one pictured but without green stuff visible. Bad for me is that I now want that heat shield that was missing because previous owner never put anything he deemed unnecessary back on the truck. So far I still count myself lucky any time I find more than 66% of the bolts or screws pesent. Looks like I will be crawling under every GM small block at the auto dismantle until I find that prize. Then I will make the change, mine is mostly intermittent and reads 60 until thoroughly heated up and then reports 45-50 until it cools off again. I will probably delay fussing with this until next oil change puts me in the vicinity with tools in hand. If anyone can help me narrow my search by identifying potential donor vehicles I would appreciate it...

[rhandwor]

Originally Posted by Schurkey

The oil pressure sending unit that supplies signal for the 0--60 psi gauge on the dashboard of the TBI-era V-8 engines is a known "common-failure" part.

I had a spraying-oil type of failure which put the final nail in the coffin of my sending unit, which has been reading considerably higher pressure than it had any right to for a couple of years now. (The previous sending unit was replaced because it indicated too-low oil pressure)

My usual supplier is NAPA; and the sending unit which had just failed was a NAPA purchase back in about 2003 or so. When I tried to buy another replacement oil sending unit at NAPA, I discovered that the part they're currently selling does not fit my '88 K1500 5.7L. The diameter of the sending unit is so huge that the heat-shield has to be forced into place; but even worse is that the sender hits the engine block before it can be screwed-into the pipe-and-80-degree elbow arrangement that GM provides.

The original sender and heat-shield on left, and the too-large sender and NAPA part-numbered box on right:


Original sender and OEM eighty-degree pipe/elbow on left, too-large sender and 90-degree elbow/pipe that I tried to make work. (Failure--if it's far enough out from the block, it runs into the exhaust.)


Far as I can tell, NAPA (p/n OP6649) and O'Reiley's both catalog the wrong part number, and they don't fit. CarQuest catalogs a different part number (p/n 57013), and those fit reasonably well. I returned the NAPA sending unit, and installed the CarQuest sending unit.

(Edited: See post #3 for current part numbers)

They do make 45 degree elbows if you search.
http://www.ebay.com/itm/201639129949/

[Schurkey]

Originally Posted by TiVoPrince

I now want that heat shield that was missing because previous owner never put anything he deemed unnecessary back on the truck.

Digging around the CarQuest web site, I stumbled upon an aftermarket version of the heat shield.

CarQuest doesn't have a photo, but the description sounds good. P/N S4049S.

That number crosses to O'Reillys (Standard) P/N PS381. The O'Reillys photo shows it's very similar to the GM item except for the spring clips at the bottom (big end) that hold it in place. There's three friction tabs on the replacement shield, rather than bigger, more-involved spring clips like the OEM.

https://www.oreillyauto.com/detail/c...?q=PS381&pos=0

[maxwedge]

My wife is giving me a t shirt that says "does anyone know what they are doing?". Lol