This car is possessed!
53bruce
08-22-2004, 09:27 PM
Help Friends!
This story seems to be just too common...
I have a 91 olds, 3.1 Multiport FI and it wont start. in kinda ran in the past, then it just quit about 5 miles from home and hasnt started since. I think I have tried just about everything, but like a previous post, it wont fire unless I squirt some gas into the air intake. Its been quite a journey getting this far, when it quit, the injectors seemed to be injecting fuel, but no spark.
After 2 ignition modules, I finally got a module that works. The spark is nice and bright now, but now, to my intense dismay, now the fuel injectors arent injecting. I checked the resistance on each injecter ( about 12 ohms each) rang the cabling back to the computer, in fact, I rang back all the sensors back to the computer and all wires seem to be OK. Then I checked the resistance of each sensor back at the computer and they appeared to be OK. The fuel rail has plenty of pressure ( about 35psi) and I have 12 volts present at the injectors when the ignition is ON. BUT, when the engine cranks, the computer isnt pulling one side of the injectors down to o volts so they wont activate.( I put a 12 volt lamp on 1 of the injectors and it wont light either) If I put 12 volts manually across the injectors, they will open and put fuel in the engine ( and then it will start and run for a bit.)
So,
The questions that I have,
1. I rang back the crankshaft sensor and it shows about 290 ohms, is this normal? It seems to be enough to fire the spark plugs, but not sure if its too low to fire the injectors.
2. the obvious, the possibility that the computer is defective and injector control circuitry is blown
3. any other insignificant device that will shut down the fuel delivery?
4. The coolant temperature sensor, often mentioned in other posts, appears to meet spec at 75 degrees its about 2800 ohms
This seems to be the last thing to correct and the car may resume a happy life. otherwise, the next trip this car takes may be to the junkyard!
Thanks for all suggestions...
This story seems to be just too common...
I have a 91 olds, 3.1 Multiport FI and it wont start. in kinda ran in the past, then it just quit about 5 miles from home and hasnt started since. I think I have tried just about everything, but like a previous post, it wont fire unless I squirt some gas into the air intake. Its been quite a journey getting this far, when it quit, the injectors seemed to be injecting fuel, but no spark.
After 2 ignition modules, I finally got a module that works. The spark is nice and bright now, but now, to my intense dismay, now the fuel injectors arent injecting. I checked the resistance on each injecter ( about 12 ohms each) rang the cabling back to the computer, in fact, I rang back all the sensors back to the computer and all wires seem to be OK. Then I checked the resistance of each sensor back at the computer and they appeared to be OK. The fuel rail has plenty of pressure ( about 35psi) and I have 12 volts present at the injectors when the ignition is ON. BUT, when the engine cranks, the computer isnt pulling one side of the injectors down to o volts so they wont activate.( I put a 12 volt lamp on 1 of the injectors and it wont light either) If I put 12 volts manually across the injectors, they will open and put fuel in the engine ( and then it will start and run for a bit.)
So,
The questions that I have,
1. I rang back the crankshaft sensor and it shows about 290 ohms, is this normal? It seems to be enough to fire the spark plugs, but not sure if its too low to fire the injectors.
2. the obvious, the possibility that the computer is defective and injector control circuitry is blown
3. any other insignificant device that will shut down the fuel delivery?
4. The coolant temperature sensor, often mentioned in other posts, appears to meet spec at 75 degrees its about 2800 ohms
This seems to be the last thing to correct and the car may resume a happy life. otherwise, the next trip this car takes may be to the junkyard!
Thanks for all suggestions...
53bruce
09-09-2004, 10:42 PM
OK, I think I finally got to the bottom of this!
Here is what I found:
First, I replaced the crank sensor as the original reading seemed too low at 290 ohms. the new sensor reads 900 ohms, a considerabile difference. but the car still would not start. I compared with some junked cars, they also were at 900 ohms on the sensor, so the sensor replacement was problably needed anyway
I had meticulusly checked each and every wire in the engine on all sensors and components to the computer from pin to pin, but the engine still would not work at all!( but everything still seemed to be right)
Then, by a stoke of luck I saw on the schematic the the engine computer picks up the ground on the 6 pin connector of the ignition module, so I rang out the path through the module back to the battery and SURPRIZE, it was open. Better, when I moved the 6 pin connection back and forth, I could see the connection making and breaking. So I squeezed each and every pin of the ignition module cable connectors and now THE ENGINE WORKS! :-)
Happy Happy Joy Joy
This is how you can fix this issue:
First, disconnect the battery negative lead, ( so nothing will get damaged)
then, unplug the 3 connectors to the ignition module on the lower front of the engine. these connectors are the DC power, on RH side, the crank sensor and the 6 pin computer interface connector on the left side.
NOW, VERY CAREFULLY, look at the female pins in all 3 connectors, they will be small square shaped. This issue is that when the connecters are attached to the module, the male pins in the module may NOT be touching the female connectors. so, I took a very small pick and CAREFULLY wedged the female pins up out of the connector body about 2 mm, then used a minature pliers to squeeze them very slightly, then pressed them back into the connector, so that when they were connected, they will touch! (BUT, Dont crush them too much, then the connectors wont fit and you could be starting a bad day.. )
after the connectors are back in place, check that other connections are secure, then return the battery connection and try to start the car. with any luck...
Here is what I found:
First, I replaced the crank sensor as the original reading seemed too low at 290 ohms. the new sensor reads 900 ohms, a considerabile difference. but the car still would not start. I compared with some junked cars, they also were at 900 ohms on the sensor, so the sensor replacement was problably needed anyway
I had meticulusly checked each and every wire in the engine on all sensors and components to the computer from pin to pin, but the engine still would not work at all!( but everything still seemed to be right)
Then, by a stoke of luck I saw on the schematic the the engine computer picks up the ground on the 6 pin connector of the ignition module, so I rang out the path through the module back to the battery and SURPRIZE, it was open. Better, when I moved the 6 pin connection back and forth, I could see the connection making and breaking. So I squeezed each and every pin of the ignition module cable connectors and now THE ENGINE WORKS! :-)
Happy Happy Joy Joy
This is how you can fix this issue:
First, disconnect the battery negative lead, ( so nothing will get damaged)
then, unplug the 3 connectors to the ignition module on the lower front of the engine. these connectors are the DC power, on RH side, the crank sensor and the 6 pin computer interface connector on the left side.
NOW, VERY CAREFULLY, look at the female pins in all 3 connectors, they will be small square shaped. This issue is that when the connecters are attached to the module, the male pins in the module may NOT be touching the female connectors. so, I took a very small pick and CAREFULLY wedged the female pins up out of the connector body about 2 mm, then used a minature pliers to squeeze them very slightly, then pressed them back into the connector, so that when they were connected, they will touch! (BUT, Dont crush them too much, then the connectors wont fit and you could be starting a bad day.. )
after the connectors are back in place, check that other connections are secure, then return the battery connection and try to start the car. with any luck...
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