Thread: LT1 Engine stopped while running

Tweet

My 1994 chevy LT1 engine stopped while running. Testing found no ignition no fuelpump pressure. Does the computer have a shut down ability? I have replaced the ignition module, ignition coil and fuel pump. The fuel pump relay appears to be working. Help

PCM Ingition fuse?

I Checked PCM fuse. It is OK. Is the ignition and fuel pump linked thru the computer?

have you checked your oil pressure. when the oil pressure gets low the engine has a shut off for the fuel.

Check the ignition fuse to.

Originally Posted by jyardgirl

have you checked your oil pressure. when the oil pressure gets low the engine has a shut off for the fuel.

The oil pressure has been quite good on this engine. Where is the "low oil pressure fuel shut off switch"? Is there a test for it? I have a problem with the fact that the ignition and the fuel pump shut down at the same time.

I believe it's in the block back by where a traditional distributor would be. I should know this, I just rebuilt the motor in my wife's 95 Z28. I hope I remembered correctly!


Keith

you are right blwn. it is at the back of the engine.

Thanks for the help. The situation is complicated by the fact that the car stopped 75 miles from home. I have checked everything but the oil pressure switch. I am going to drive the 75 miles to visit my 94 Chevy Caprice station wagon. My concern was the way it stopped while running and both the fuel pump and the ignition are not working. It stopped as if I shut it off. Could that be the problem????????? It happened at night. The headlights remained on. The check engine light came on and I costed to a stop. The engine cranks.

Can I get to the wires comeing from the ignition switch to see if it is functioning? There are 4 wires comeing to the coil. Can I test at this point to see if the ignition switch is working? HELP

When you turn the key to the run position, you should hear the fuel pump come on then go off. Does that happen? Another question is how many miles on the currently installed Opti Spark? The Opti Spark is the distributor located under the waterpump. If the waterpump leaks, say goodby to the Opti! They are notorious for just quitting. How have you checked your ignition? Did you pull off a plug wire and crank or use a timing light? I would think without the luxury of a diagram, even if the oil pressure switch was bad it would at crank, start and then die.

Keith

When I turn the key to run position the fuel pump does NOT come on. The ignition was tested by pulling a plug grounding the plug and cranking the engine. I hope I can get the distributor off without removing the water pump. Thank you for the help.

Like Blwn31 said, not having a wiring diagram makes it hard to diagnose but on my aftermarket system the fuel pump gets it's signal from the ECU (through a relay) and it did the same thing once - running fine until I plugged in a hand held calibrator. It blew the in-line fuse to the ECU, dropping power to my coil, injectors and fuel pump. A new 3A fuse feeding the relay to the ECU brought it all back to life. I now carry a bag of fuses.

try switching relays for the fuel pump---there are 2 or 3 the same in the underhood fuse panel
Also try a differant key as the resistor in the key is matched to the computer and anti theft box

if the ecm doesn't receive a signal from the crankshaft sensor it will not trigger spark or injector pulse or fuel pump power so that's where I would start ......ted

Sounds like the Opti-spark distributor has failed. It is behind the water pump and the pump has to be removed to access. Here is a test...
.1 Check the operation of the optical distributor.

2. Disconnect the distributor 4-wire harness connector, then turn the ignition on. On the Powertrain Control Module (PCM) side, check for a 5-volt reference on both the low resolution (Red/Black) and high resolution (Purple/White) signal wires.

3. Verify that there is battery voltage on the Red wire and a ground on the Pink/Black.

4. Plug the connector back in. Check for good square patterns from both the low and high resolution circuits at idle or while cranking the engine. If a lab scope is not available, check for about 1 volt DC during cranking on the low resolution signal and about 2.5 volts DC during cranking on the high resolution signal.


5. If the signals are erratic or flat line 0 or 5 volts, check for bad, chafed wiring to the distributor. If all OK, replace the distributor

The opti spark distributor is bad about the bearing in the base to fail and actually melt the rotor or damage the module. Either way...it would be best to have it towed to a reputable shop and have it diagnosed and repaired there. Rough cost of the opti spark is 400.00 plus install


Btw...if the oil pressure sending unit fails it wil still have fuel pressure......You probably do not have injector pulse