1990 Chevrolet Corsica

Engine Performance problem
1990 Chevy Corsica 6 cyl Front Wheel Drive Automatic 147000 miles

The original problem was that the rear main seal was leaking along with some minor coolant leaks. Then one day the 20 amp fuse blew for the fuel pump. The fuse was replaced and the fuel pressure was measured at just 36 psi.
Fuel pump - pressure now about 45 psi.
Fuel lines and filter are new from pump to engine.
Oil pressure switch (twice) and connector are new.
Fuel pump relay replaced.
Rear main seal and intake gaskets.
Plastigaged crank and rod bearings to make sure they were within tolerances.
Oil pump.
Switch to 20W - 40W oil.
Engine starts when cold and runs approx. 5 minutes and dies. When cranked - no immediate fuel pressure, however it rises slowly to normal after a 5 - 10 seconds but still no start UNTIL several hours pass.
August 3, 2010.

When it dies have you checked for spark at the plugs? Has check engine light come on? Have checked for codes?
Let me know
Thanks for donate

Aug 3, 2010.
Actually - no codes. Started it this morning - easy start. Ran about 1 minute and died. Fuel pressure about 44 and plenty of spark. Test all three wires on front of engine with a spare spark plug. All three showed bright white spark and the fuel pressure stayed above 40 psi.

Pretty wierd - don't you think!

Aug 5, 2010.
Need to check Crankshaft sensor to locate see diagram

Check connector for any moisture ie. from coolant leak. if good with OHM meter measure resistence across terminals 900-1200 OHMS. Next set meter on 2 V AC scale leads on terminals to sensor crank must be.1 volt or higher. if either fail replace sensor. If have NOID light think you can get to # 6 INJ. hook up see if it flashes when it dies.

Aug 5, 2010.
Okay - will check ohms and voltage at crank sensor.

Messed with it this morning some. Have an Actron scan tool. Saw something I never saw before. When I put the tool in field test - the ecm flashes a 12 and the surpirise was that the cooling fan runs.

Also managed to keep it running a bit and noticed that the coolant temperature hits 230 and the cooling fan does not kick on - but the engine refused to run after that.

Aug 5, 2010.
In my case the crank sensor is between the engine and the transmission. With the car on jack stands I have extremely limited access to the unit and cannot line up my Fluke probes to get an ohm reading. I did punch into the wires and with the ignition on the voltage reads 0.035.

I appreciate your help very much.

Aug 5, 2010.
Follow sensor wire up to connector unplug make readings there. Also sensor needs to be unpluged and engine cranking to make voltage reading.
As for temp OHM check coolant sensor near Thermostat housing engine cold 3400 ohms engine at 210-185 ohms

Aug 6, 2010.
Its time to get you up to date.

Crank sensor was cracked - replaced.
Finally got a code! 33 then after a reset a 34. So, being totally confused - I replaced the MAP. Still came back with a 34.

Engine now will not run at all but a cylinder occassionally fies.

Checked crank manifold pressure - no vacuum unless a cyclinder occasionally fires.

Replaced fuel pressure regulator.

Tried noid light on #6 - no light. I guess maybe some of the injectors are not firing!

Tried uncoupling the exhaust pipe to rulle out plugged Cat Conv.

Even though the ECM is new - still using orig Prom - I guess I will pull ECM and have it reprogrammed early in the AM.

Further checking reveal a worn through wire to #4 injector - repaired - still no start.

It tries to start when the engine is first cranked but fails. Further cranking is futile!

Can you think of anything else?

Aug 15, 2010.
Seems to be going down hill now won't run at all? Was there power to injector? Still have spark? All this started when rear main was replaced?

Aug 16, 2010.
Oddly - it started right up yesterday AM. It ran nice for 30 seconds and quit - then refired and ran for another 30 seconds - then quit and hasn" t started since.

Dealer only on ECM reprogramming - probably something I can't afford.

Replaced coolant sensor near thermostat - no change.

Only 4 things and sensors left: knock sensor (local major parts supplier has sold 3 in the last 5 years - sounds like a very long shot!), O2 sensor, purge control for cannister, Camshaft Position Sensor? And a sensor I can't identify on rear head near the throttle body (doesn't show up in wiring diagrams either) with a light green wire and a green wire with a black stripe the seems to go into just 1 wire at the connector.

Aug 17, 2010.
ECM reflashed - no issues. 4 other mechanics have 8 - 10 hours in it without results. They even disconnected the entire A/C system to eliminate that.

Please re-think this and see if you can come up with something.

Aug 23, 2010.