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Discussion Starter · #1 ·
This morning i was thinking how my wagon needs an oil change, just about due, nest thing you know, 'low oil light' comes on briefly, while oil pressure goes to 0 and engine dies. Tried changing sending unit, to no avail. Engine turns over fine, but won't start. I'm sure the pcm has a safety feature for cutting the engine with no oil pressure. So i've started taking it apart to remove the engine and install a new pump. Any other ideas i should try before i get too far...oh wait too late. :0
 

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Mine did that when i had a vacuum leak at the TB. Any kind of stumbling before it died??

Mine low oil light always comes on when my car stalls and dies btw.....
 

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Did you check the oil pressure switch? They're known to go out far more often than the pump. Could also be a larger electrical issue, since you say the low oil light came on as well. This light and the pressure switch are unrelated.
 

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I once broke an oil pump driveshaft retainer ring... the end of the shaft where it meets the pump then broke and the shaft fell in the pan. No oil pressure.

"check gauges" lit up in the dash but the engine never cut... the oil pressure needle was at 0. I drove it 1/4 mile further down the street to where I work and replaced the oil pump and driveshaft (once that doesnt have a plastic retainer bushing).

The engine ran great for 2 years after that and even saw a few 11 second passes with nitrous. :D
 

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I'll check that as soon as i find the switch :)

It's at the top rear of the block, just a bit to the driver's side behind the intake manifold. The switch is designed to ground out the fuel pump circuit, and shut down the car. I believe the layout of this curcuit varies from '94-'96, but the end result is the same. If you unplug the switch, and it is the culprit, the car SHOULD start.
 

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My dad just had a similar problem in his '95 DCM. Any time you jumped on it, as the rpm's got just about to the shift point, the motor would cut out and stumble and the check gauge light would come on (and sometimes the low oil light, too). As it turns out, the pickup came off the oil pump. Replaced the pump/pickup (welded the pickup this time), problem solved. I'd definitely try the switch first, though, as it is MUCH easier to replace--good or bad--and it's cheap.
 

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Discussion Starter · #9 ·
Disreguard the oil pressure sensor, i was wondering what the switch was, same thing. Already replaced that, didn't to the trick, been working on pulling the engine. We shall see what the deal is. Motor only has 114,000 miles on it, but then again it IS 15 yrs. old.
 

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You verified spark and fuel pump operation first, right???
 

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If you have no oil pressure your car should still run for at least 5 seconds before the PCM shuts the motor down. Did you check your oil level?
 

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Discussion Starter · #13 ·
Might get the motor pulled tomorrow evening, so well all find out soon what it is. I happen to have a high volume oil pump on a shelf, and may be picking up a few 'goodies' as well to add in while the motor is out. Like an LT4 hotcam, ported/polished corvette heads/manifold...etc..
 

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Discussion Starter · #14 ·
Well, here's the scoop... nylon drivesahft ring is intact, but a crack all the way through it. Also the plastic cover on the inside of the pan for the oil level sensor is broken off. So i'll be replacing those two parts, also install my high volume oil pump sitting on the shelf. Then i might just put it back in the car and leave the rest alone. Going to put on my stock manifolds and all, so i have Hooker headers for sale. I can get another motor with ported/polished corvette heads and intake, almost brand new, and it also has new valvetrain and LT4 hotcam for next to nothing. Thinking about passing it up..im short on cash, but it IS tempting. I need to leave well enough alone but it's just so hard sometimes.
 

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make sure you install the oil pump driveshaft that does NOT use a plastic bushing, and weld the pick-up tube to the pump... they almost always fall off.
 

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Discussion Starter · #16 ·
^ Affirmative, was planning on doing both :) Might have a complete 114k LT1 for sale that works flawlessly shortly. Waiting to hear back on other LT1/LT4 Corvette motor.
 

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Dan I am proud of you....you have not touched that motor since you owned it....new record?
 

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Discussion Starter · #18 ·
It's been 3.5 yrs., put everything back together, ran it for about 10 mins last night before it started acting up and quit running again, it then started this morning. I bought another pcm today, that's next on my list.
 

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Sorry, so much bad info here.

On a 94 , the PCM knows nothing about oil pressure and will not shut of the engine.

When you turn on the ignition, the PCM grounds the fuel pump relay running the pump for a short period as soon as it sees ign power.

If it sees a signal from the Optispark that the engine is turning, it continues to keep the fuel pump relay grounded, powering the fuel pump.

If not it opens the relay , stopping the fuel pump.

The oil pressure switch is redundant, once there is oil pressure it closes taking the load off the relay.

If the pressure drops, the pump continues to run because of the relay

If the relay dies the car still runs but has extended cranking times.

Yes, if the relay was already dead , the engine would die if the oil pressure dropped to the point the fuel pump shut off but that is not the purpose of the system.

The oil pressure switch has three terminals.
Two to bridge the fuel pump relay as mentioned above.
The third is switched to ground (or variable resistance to ground in SEO cars) to run the gauge. NO interconnection to the PCM at all.

FYI, in 96 they dropped the redundant pressure switch and simply used it for the gauge or light.
Gerry
 

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Discussion Starter · #20 ·
Tried a pcm for the hell of it (before i saw post^), and it is NOT starting. Cranking but not starting. Fuel system is good, i didn't thnk the opti could be bad, but i suppose, reason being is i just put in a Summit opti last year. Maybe they are junk. So i'm still without the car. Almost to the point of junking it if the car continues to give me problems.
 
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