Engine dies suddenly when low oil level light comes on.

1994 Buick Roadmaster wagon, 199,650 miles, only engine mods are Home Depot CAI, 160 deg. thermostat, TB by pass. 4,000 miles ago I replaced

the Opti, ign. wires, water pump, coil, and a bunch of old dried out vacuum lines.

This afternoon I was driving down the road at about 60 mph and the low oil level light (not the oil light) came on and the engine shut off and wouldn't

restart, no other lights came on. Pulled over and parked it, everything still looks plugged in, no unusual smells, leaks, noises, and the oil level is about a

1/4 of a quart down, still ok. Went back home got a few tools, and came back to the car with my father-in-law. The car started for a few seconds and

then shut off again when the low oil level light came on. I disconnected the battery for a few minutes while I hooked up the fuel pressure gauge,

reconnected the batt., but would not restart, fuel pressure was at 40 psi., but the timing light was not flashing when hooked up trying to restart so I guess

no spark. So We towed it home, about a mile away.

Got it in the driveway, still cranks, but no start. I let it sit for about 15 min. and tried it again, It started and ran for about 20 seconds then died again.

Would not restart. There is oil flowing at the top of the engine, and the fuel pressure has not dropped below 41 psi when cranking. After I let the car sit

again for about 40 min. the car started again, ran for about 30-40 sec., and even reved it up a little, low oil level light came on and it died again.

That's my story, anyone have some ideas? I can see in the FSM that the oil light/ oil pressure sending unit is connected to the fuel pump, but it doesn't

look like the low oil level light/sending unit is connected to anything that would shut the engine down. Is that right, or am I blind?

Thanks, Mike

I BELIEVE there is a fuse for the oil pump. If that goes out, the PCM shuts off the engine to save it. Explains the run for 20 seconds then shuts off.....

All fuses, under hood, and in drivers side dash are good.

This may sound stupid but are you sure that the low oil level light isnt coming on as the engine stumbles and then stalls?Years ago I had a Monte Carlo that did the same thing and I got lucky and diagnosed a clogged fuel filter which cured the problem completely.It was dumn luck that I ignored the oil light and started looking into the fuel system.It would also start and run for a few seconds then stumble,oil light comes on and then it stalls.Just my 2 cents.Please let us know what it is just in case I get to gloat a little.
Take Care
Flasheroo

Yeah, I'm sure, just the low oil lev light comes on a second before she takes a nap. It does not stumble and die, it just dies like flipping a switch. The fuel filter was also replaced about 4,000 miles ago.

Further info: Temp outside was low 50s, no rain, dry roads.

Yea, I don't knkow much, but I'm also not sold on the light being an indicator of cause, as opposed to it being a side effect.

Hopefully it's easy and somebody will hook you up.

I'd have to dig through my shop manuals, but I thought the engine was set to shut off if you lost oil PRESSURE, but not due to low oil level.

Let me do some digging. If so, bad sensor?

Yeah, your right Mike, that's why I'm kinda baffled. May be Bewbers on the right track.

A failed fuel pump relay for one.

Even knowing what was going on, it took awhile to confirm what you were seeing in the manual. Both the '94 & '96 FSM's were unclear on the setup, it was a spare Haynes manual that confirmed something was amiss with the factory wiring diagram.

The combination "fuel pump switch & engine oil pressure sensor" is called out in the instrument panel diagram, but not even shown in the fuel system wiring schematic. The entire switch, wires and splices are missing. Strange as usually the GM stuff is usually right there on the electrical circuits.

Anyway this is how it works:

Most, if not all, GM's of this era are wired so that an oil pressure switch backs up the fuel pump relay. If the fuel pump relay should fail, once oil presure builds, the relay is bypassed by the oil pressure switch to permit the car to start anyway. This is probably what you've had going on for awhile, an indication is a longer than expected crank time, waiting as the oil pressure builds to energize the fuel pump. While we're here, the oil level indicator is illuminated through the PCM, but has no control circuits associated with it.

You have two problems though, the more serious is the oil pressure taking a nose dive. The FSM calls out a 4 PSI setpoint on the switch, if that is correct - and the oil level light coming on indicates that it is something in the lubrication system - you'll really want to get to the bottom of that one soon.

- J

I think I figured it out , ICM. Bewber was right, light was a side effect and not a
symptom. I've never seen that light on my car before. I'll know for sure tomorrow
night when I put the new one on after work.

I appreciate all the help guys, and Thanks J for the time you put in looking all that up.

I forgot the KISS rule, Keep It Simple Stupid. I tried to over think the problem.

I'll update tomorrow night, good or bad.

Mike

Well I put the new ICM on, but the car won't even turn over now . Batt. good, but the pass key light is on now when I turn the key to start, and the starter starts to tuns a little bit when I wiggle the steering wheel, so I have to put in a new lock cyl. tonight.

Ding dang, strike 2, lock cyl. didn't fix the no crank, but I found a broken ground under the, uh, Coil/ICM mount, wonder how that happened?

So back to the engine stalling thing, I barrowed a scan tool and it read, DTC 16 No low res.pulse, or something like that. So I went through the FSMs flow chart for DTC 16 and said to replace the distributor. I just did that last June and only put 6,800 miles on it. I checked the vent hose, that's ok so I ordered a new opti from thepartsladi on ebay. The opti I got last year was $89.00 plus shipping on ebay from chandlermotorsports. Bewber was right, the low oil level light meant nothing.

Lessons learned, don't buy cheap optis, and check your work, carefully.

200OZ wrote:

This afternoon I was driving down the road at about 60 mph and the low oil level light (not the oil light) came on and the engine shut off

engine shut off at 60 mph,. whoa!!,.

auxilliary bat post??

Nick

I have a new opti and wiring harness coming, is there an updated vent harness available?

The aux. batt. post is the brass one.

i,ve never seen an opti just fail like that,.. oh wait i have,.the rotor screws came off on one onetime,..i could shake it and it rattled,. just put two screws back in with locktite and i was good to go,..

Nick

Well, it doesn't rattle when I shake it, but I only paid $90.00 for a new in the box unit from eBay , could that have been the problem?

sorry, but the crystal ball is kinda cloudy,.. maybe hold it closer to the screen??

nick

I got the new opti in last night, problem fixed and the car run great.