Not enough oil pressure to start vehicle

C

c4 Travis

Member
Out of nowhere, my 85 C4 became a no-start. I tinkered for a while before I ran across a grumpyvette post from another forum that led me to the oil pressure switch.

I jumped the connector and the car started right up. Satisfied that I had isolated my problem, I happily purchased a new oil pressure switch. The new oil pressure switch would not start the fuel pump and I am still jumping the connector to operate the vehicle. Suspecting an obstruction, I removed the switch, gauge, and the tree that held them. I cleaned and inspected everything and reassembled. The car actually started 4 times afterward with some extensive cranking. It didn't last though and I am jumping the connector and bypassing the oil switch again. The readout on my dash during cranking reads 0-3 psi and I believe 4 is required.

Any thoughts on why my pressure is so low and how I can increase it?
 
first step Id suggest is changing the current oil and oil filter out for a decent 10w40 oil (6 quarts,)and a WIX or PUREOILATOR oil filter and then testing your oil pressure with a separate oil pressure gauge, as it sounds like its a oil pressure gauge, fuel pump relay pressure sensor issue or oil pump issue at this point.
now I have seen a couple times where the oil pump pick-up came loose from the pump or vibrated down so it rested on the oil pan floor and that in those cases dropped oil pressure to near zero, so obviously pulling the oil pan and installing a high volume oil pump and welded on pick -up is an option here
you don,t want to assume anything, but you do want to test a few parts and carefully inspect the car looking over every potential detail that might relate to your problem,, simply replacing the oil and filter and testing with a separate oil pressure gauge is a good start, but I,d also suspect the oil pump pick-up might be loose,
an inspection tool like the one linked below, while the old oild been drained, will allow a casual inspection of the lower engine internally without pulling the oil pan if used thru the oil pan drain plug hole, this is also a great way to easily locate and verify you have a 4 bolt vs two bolt main cap engine, without pulling the oil pan, or inspect for a loose oil pump pick-up.


http://www.toolrage.com/prodView.asp?sku=SLI-PV618

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viewtopic.php?f=62&t=881&p=8362&hilit=leak+down#p8362

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IVE CHANGED SEVERAL OIL PUMPS IN C4 CORVETTES with the engine still in the car , this thread should help
viewtopic.php?f=32&t=459

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Thank you for the quick response!! I will definitely change to the suggested oil and filter. Once the car is running I'm reading anywhere from 12-30(at idle) to 20-40 (during acceleration) but there is no rhyme or reason to how these numbers vary. Is this normal?
 
if your engines clearances are larger than normal due to wear issues oil pressure will be low, but in most cases its the oil pump thats come loose or the oil pump pick-up thats clogged or loose or defective gauges or sensors, personally Id have pulled the oil pan, and installed a new oil pump as a precaution by now and pulled a few main caps and rod caps and inspected the bearing condition, as dropping the oil pans just not that difficult or time consuming, even if your working on jack stands and have little experience and a new oil pump and gaskets is well under $100, if you were local I,d suggest you drop over and we could replace the oil pump and check out the sensors and connections.


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http://www.summitracing.com/parts/slp-224-4143
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Thanks! It's my first Vette, so I'm getting to know her quirks. I love her but she sure does keep me busy!

I will get to work on this now. Thanks again for sharing your knowledge with us!

Trav
 
I agree with Grumpy.
I would pull the oil pan down. Inspect.
Sure sounds like its oil pickup screen related issue.
A tell tale visual sign is a dent or large crease in the lower oil pan sump by drainplug.
Takes only one hard blow to the oil pan to knock the stock pickup tube loose.
I always MIG Weld tack a new pickup screen to the pump.
At least 2 places.
If your experienced welder you can weld fully around pickup tube to to the oil pump.
Did that last in June on my Suburban when I replaced the crankshaft with a Scat crankshaft.
 
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