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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / April 2006Chev Cavalier 91-V6 FI, Engine stopped suddenly and wouldn't start, please help.
Chev Cavalier 1991 V6 MFI, engine suddenly stopped while driving and wouldn't start again. Checked: plenty of sparks, fuel pump working, has fuel upto the Schrader valve on the fuel rail assebmly, the engine rotate while trying to start but wouldn't start. > Chev Cavalier 1991 V6 MFI, engine suddenly stopped while driving and > wouldn't start again. > > Checked: plenty of sparks, fuel pump working, has fuel upto the > Schrader valve on the fuel rail assebmly, the engine rotate while > trying to start but wouldn't start. Does the engine sound different than before when it turns over? No, it sounds normal. > No, it sounds normal. What if you tried using starter fluid or gas in the throttle body. I didn't try that yet. I kindof feel that it has got something to do with those injectors, the fuel rail assembly is full of fuel, but not reaching the cylinders. It is likely that the injectors were not activated to pass the fuel from the rail to the intake manifold. Having said that, I have not been able to locate the wiring diagram of the injectors, according to the manual, the injectors are controlled by the ECM, but I'm not sure where the wires and relays (if there is one) are. Another thing I would like to know is how to chech if the injection signal (from ECM?) has been passed on to the various injectors while the engine is turned over, there is nothing can be found on the manual I have. Thanks very much for you response. I have just check the code, only code "34" is set. On the manual for this model, there are two possibilities, either Mass Air Flow sensor or circuit, or Manifold Absolute Pressure sensor circuit. I guess I got to check these two sensors tomorrow? You have either a Mass Air Flow sensor or a Manifold Absolute Pressure sensor, not both. My 1992 3.1 has a Manifold Absolute Pressure sensor. If I recall correctly this engine will run with a bad Manifold Absolute Pressure sensor. You might have a bad computer. > I have just check the code, only code "34" is set. On the manual for > this model, there are two possibilities, either Mass Air Flow sensor or > circuit, or Manifold Absolute Pressure sensor circuit. I guess I got to > check these two sensors tomorrow?  SignatureMike Walsh West Palm Beach, Florida, U.S.A. I have checked the Manifold Absolute Pressure sensor according to the procedure in the manual and it appears that the sensor is at fault. The procedure is ".... Unplug the electrical connector from the sensor and, using jumper wires, connect terminals A and C (the two outside terminals) to their corresponding terminals in the electrical connector. Connect the positive lead of the voltmeter to terminal B (the center terminal) of the sensor and the negative lead to ground. With the ignition on (engine not running) the voltage reading should be about 4.5 to 5 volts. Start the engine and let it warm up. The reading should now be different from the original reading, and should fluctuate with changes in engine rpm. If it doesn't, check the vacuum hose for breaks or blockage. If the hose is OK, the sensor is probably bad........." My reading was "0" volts from the center terminal in the electrical connector while the ignition On, I couldn't see if it fluctuate since my engine couldn't be started. One thing, how could the sensor has 4.5 to 5 volts when the electrical connector is not connected? Does the manual mean the center terminal in the electrical connector? I have also checked the center terminal in the electrical connector and the reading is also "0" volts. I agree that the engine should run with a bad Manifold Absolute Pressure sensor, however, it may depends on how bad is the sensor. It seems that my Manifold Absolute Pressure sensor is dead, so it should not be ruled out that the Manifold Absolute Pressure sensor is the root cause of not starting. In article <1144508704.470617.269590@z34g2000cwc.googlegroups.com>, > One thing, how could the sensor has 4.5 to 5 volts when the electrical > connector is not connected? That's what the "using jumpers" part is for. (IOWs, it's not disconnected) Yes, I redid the test and the voltage is 4.75V, within the specification. It seems that the next possible suspect is the computer module, Mike, if you are still following this thread, may I ask what happened to the 1992 3.1 engine, did you have to change the computer module, or something to that effect. Thanks again for all the response above. I haven't had any similar problems with my Beretta, but most engines since about 1990 use a manifold absolute pressure sensor, throttle position sensor and crankshaft sensor (for engine speed) to control fuel flow. It is possible for the engine to run reasonable well with any two of these sensors. I don't recall if the GM engine is able to run with one of the sensors bad, and I am not home so I can't look in my manual. The fact that you have ignition indicates that the crankshaft sensor is working. Check the throttle position sensor if you have the specs for it. Pull a couple of spark plugs and see if they are wet with gasoline. If they are dry the injectors are not working. If the throttle position sensor and MAP sensor are good and the injectors still don't work you probably have either a bad computer or a bad connection somewhere. If any of the sensors are bad you should get a failure code from it, but is best to check them with a meter if you can. You can check the voltage on the fuel injectors, but the pulses are so short when cranking that you will probably need an oscilloscope to see them. > Yes, I redid the test and the voltage is 4.75V, within the > specification. [quoted text clipped - 5 lines] > > Thanks again for all the response above. SignatureMike Walsh West Palm Beach, Florida, U.S.A. Thank Mike, It finally comes down to the simplest: the timing chain broke! I opened the front volve cover and turned the engine over, nothing moves, all the six volves are not moving at all. So it seems that when I'm turning the engine over, the only thing rotate is the crankshaft, the camshaft don't move at all. I'm going to remove the timing assembly, and probably replace all the related parts. Thanks again Mike, for all the helps. > Thank Mike, > [quoted text clipped - 8 lines] > > Thanks again Mike, for all the helps. Interesting. Earlier you said it did not sound different turning over. When my 2.2 cam chain went, it could tell right away something was different. The sound was different and it spun faster. Bob It did sound no different to me, as well as to an old mechanic who has over 40 years of backyard mechanic experiences. I guess this may be dependent on the position of the volves when the chain went? Another possibility is that, due to the fact electronic components break down very often now days, people tends to develop a tunnel vision that first thing to look is the electronic component when something went wrong. I should have suggested a compression check. I saw a Chevy V6, which I think was a 2.8/3.1 engine, with a broken chain and the difference was obvious because it was an interference engine and the valves were bent. The owner however did not noticed any difference. Even with a non-interference engine there should be some difference because some cylinders will have valves closed and other have valves open. > It did sound no different to me, as well as to an old mechanic who has > over 40 years of backyard mechanic experiences. I guess this may be [quoted text clipped - 4 lines] > that first thing to look is the electronic component when something > went wrong. SignatureMike Walsh West Palm Beach, Florida, U.S.A. Thanks again Mike, I should do that. > Thank Mike, > [quoted text clipped - 8 lines] > > Thanks again Mike, for all the helps. When the timing belt on my old dirty dodge broke the engine made kind of a different hollow sound when I tried to start it. Like a different kind of a whine. |
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