3800 starts, dies immediately

[HaroldnMike]

Greetings from NC, first post. I have searched the board quite a while (thanks everyone for some great info!) and can't quite find my exact symptom. My son Mike and I purchased a 94 Lumina Van fixerupper with 120k on the clock. Also picked up a vandalized 95 that runs out great but is unrepairable for parts. Previous owner says it starts and dies, may need a ign module and/or computer. WE swapped them both out. The engine fires at once and runs smoothly for 1 to 2 seconds and dies. It does exactly this every time. From our searches we are thinking crank angle sensor but we wanted to get you folks opinion. Any and all suggestions greatly appreciated!

Harold

[Reatta Man]

Harold,

There are two sensors that will kill the engine almost immediately if they are not working properly.

One is the sensor that reads the oil pressure for the ECM. It is probably different from the sensor that sends a signal to the light or gauge on the dash. If it is not working or gets a no-pressure reading, it will kill the fuel pump in order to "save" the engine. The other one is an oil level switch that sends a signal to the ECM. I think this is the one that is giving you the problem because it takes about 2 seconds to "read" the oil level and send the signal to the ECM. Like the other one, if it is not working or reads a low level signal, the ECM kills the signal to the ignition module. This is why the engine wouldn't run after you replaced the ignition module.

On many 3.8 engines, the sensors are located near the oil filter mount. You should either get a paper factory service manual or go to www.alldata.com and subscribe to the electronic factory service manual in order to be sure. You can try one of those $10 manuals they sell in parts stores, but I'm not sure if they are detailed enough to let you know where all the sensors are located.

On an older engine, I would replace both of them just to help ensure dependability.

Good luck.

Joe

[HaroldnMike]

Brilliant idea, thank you. I have Mitchell On-Demand. According to it the fuel pump relay energizes for start then 12+ goes thru the oil pressure switch and runs the fuel pump. When I read your post I took a quick look for the switch and could not immediately find it. So if I just apply 12+ to the fuel pump at the relay that should be a good test of the switch. Paying more attention, the car actually runs for maybe a second at most. I hope to try this afternoon.

Thanks again,

Harold

[HaroldnMike]

Before starting the jumper deal I listened for the fuel pump (duh) it was running like it should. Gauge indicated 1/8 tank so I added a couple gallons of gas. Car starts and runs with much difficulty, lots of gas pedal stomping, spitting, sputtering, stalling but it runs. I'm thinking bad gas, fuel filter, plus the computer has to re-learn. Check engine or service soon (don't remember now) came on so I need to check the codes.

Thanks,

Harold and Mike

[Edward Lee]

I've just finished working on a 2001 buick lesabre with the 3.8L v6. Kept starting then immediately cut off. I replaced camshaft position sensor, crankshaft position sensor, ignition control module, and fuel pump, still did the same thing after each replacement part.  Got ready to pull the BCM and PCM and guess what I found?  A number of wires bitten into either by squirrels or rats in the wiring harness running to the PCM!  I used a few bad name calling because I lost time changing all those other parts.  At least the car is starting up faster than it ever had in the past.