Serious question

Bob NH

Bob NH

Well-known member
When I first bought this car it always showed 50 lb. oil pressure at startup and after warmup would come down to around 25-30 constant. I just noticed on a short drive the other AM pressure dropped to O and would only come back up a few lbs. and back down again. I do not dare to start it till I find out what happened. I checked today wondering if the sending unit had a loose wire and it was OK. Is there a way to test a pressure sending unit on the block ? A former owner spent "gazillions" of dollars on the rebuild including everything in the engine . I dread pulling the pan to see what has happened, I don't bend so good at my age anymore ! Ideas anyone where to start ?
 
Bob,

I would wager that the sender has had a diaphragm failure internally.
I would get down to your local auto parts store and purchase a cheapo mechanical guage and install to verify you have oil pressure.
 
IMO remove the sender and check it first.The same thing happened to a friend of mine.The sender was the problem.If you pull the sender try somehow to connect a mechanical gauge directly to the block and see what the reading is.After we had that problem I always keep an old mech oil pressure gauge for this purpose.
Big Foot answered while I was typing.
 
Big-Foot said:
Bob,

I would wager that the sender has had a diaphragm failure internally.
I would get down to your local auto parts store and purchase a cheapo mechanical guage and install to verify you have oil pressure.
Click to expand...

X2-Test it with a mechanical gauge before you tear anything apart.
 
Bob
If you find that the sender is actually OK, then
the relief spring in the oil pump may have failed.
Other than the PITA of removing the pan, an easy
fix.
 
You will probably have to pull the floor board to get a wrench on the square nut that forms the base of the sender. I bought a 4" copper nipple and brass coupler of the same thread size at the hardware store and installed it as an upward extension, so I can get to the oil pressure sender from the engine compartment. Much less bending!
 
Good to hear so many thoughts, I like the idea of extending the gauge with a nipple ext. Scary to think you might blow up a 5-6 thousand dollar engine from pump failure. Thanks everyone, appreciate it
 
Bob, if you remember my 39 P/U from the Bonney eagle show, I have a gauge in the engine compartment you could make. I have this arrangement off the top tap on the sender port and a mechanical psi gauge off the side tap, hope the picture helps you out.
 
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Klinker, looks like you have one already, what are ya trying to do, corner the "Market" ? Haha You would not want this rag, it was a national winner way back in 1980 and a V8 club Dearborn winner at some point in time. Just a beater these days !
 
Bob in NH--that is the best kind of beater I can think of. I have one myself! How's the fishing on Newfound?
 

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WOW ! Termite and carpenter Ant delight ? Beautiful and the covered bridge isn't too shabby either. Have never fished Newfound. Even though I do have a lifetime hunting and fishing NH license I never find time to go.
 
I gave up on the accuracy of the stock oil pressure gauge a long time ago. If you want to keep the "looks" you can "T" below the sender and run a mechanical gauge that you can hide in the glove compartment.
Don't panic, check as advised and please keep us posted.
 
Do like Old Henry put a set of gauges in the glove compartment, I did that om my 56 merc after engine rebuild I have to much money in her to count on dash gauges
 
I know this is kind of a stupid answer, but have you checked the oil level in the pan ? Symptom sounds similar to a very low oil level.

Sal
 
Another simple indication for an actual loss of oil pressure is the engine will become noisy--clattering where there was non previously .
 
One other thing about electric senders I've found over the years ---
The sender itself requires a good ground.
The only way to get a good ground to your engine is to NOT put any thread tape or sealant on the bottom 2/3 threads of the sender. That means the first threads that go into the block or adapter must be clean. This will give you a good connection. The sealant on the threads above that point will take care of any thread tolerance issues and seal them up.
The same holds true on any adapter fittings that your sender might be threaded into.
 
Did check oil level, looking very clean and at top of fill mark. Be a few days till I dig in to see whats up, trying to rework some 1946 CJ2A front fenders for a neighbor/friend and tearing my remaining hair out on these. BTW, different question. I have a Lincoln SP100 wire feed welder and pretty sure when I first got it after I shut off the tank valve, I could pull the trigger and gauge pressure would drop to zero. For some reason now I have to loosen the hose connection to release the gauge pressure ? I unhooked all lines right up to brass block and they are all clear. What now ? Thank you guys
 
Never did before plus a huge waste of wire when pulling trigger with power on as it continues to feed.
 
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