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Daryl
Daryl, Shop Owner, Master Mechanic
Category: Buick
Satisfied Customers: 12385
Experience:  28 years experience, Master Mechanic
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91 buick regal: wont start..crank..coils and module and the ecm

Customer Question

91 buick regal with 3800 wont start. I changed the crank and cam sensors ign. coils and module and the ecm. Plugged my scanner in and now i get a vehicle not responding error. should I replace the PROM chip?
Submitted: 4 years ago.
Category: Buick
Expert:  Daryl replied 4 years ago.
The problem is not likely the Prom, To help with this problem I would need to know if there is spark, fuel pressure and injector pulse would also help.
Customer: replied 4 years ago.
no spark i have fuel pressure and there is a buzzing noise when the key is turned on
Expert:  Daryl replied 4 years ago.
How are you checking spark?
Customer: replied 4 years ago.
had an error on my side sorry if you get this twice.
Old school way. Put a screwdriver in the wire and put it near ground
Expert:  Daryl replied 4 years ago.
Ok, you might try removing the wires on the coils and see if there is any spark there, you just need to remove the wire and crank the engine the coils should spark to each other.
Customer: replied 4 years ago.
no spark at the coils
Expert:  Daryl replied 4 years ago.

Below is what I would check first,

 

1. check the below wires

2. Disconnect the crank sensor and check for power and ground to the sensor on the White/Black and Gray/Red wires.

3. Check the connections at the ignition module for being clean and tight.

4. Verify that the Pink wire at pin P is 12 volts key on and cranking. Verify the ground on pin K Black/White wire, on the ignition module.

Customer: replied 4 years ago.
ok i'll do that. Could I be running into some sort of antitheft problem. I removed the engine and did an overhaul. Everything short of the block internals
Expert:  Daryl replied 4 years ago.
It is not likely a antitheft problem, anti-theft usually disables the fuel.
Daryl, Shop Owner, Master Mechanic
Category: Buick
Satisfied Customers: 12385
Experience: 28 years experience, Master Mechanic
Daryl and 2 other Buick Specialists are ready to help you
Customer: replied 4 years ago.
Ok cool. If the sensor has power then what
Expert:  Daryl replied 4 years ago.
The problem is a wiring problem some ware, checking the power at the crank sensor and the module is the place to start it is most likely one of the two. So when you figure out which one does not have power or a good ground the wiring will need to be tracked down from there. SInce the engine was out I would be sure all the grounds to the block are good and tight to start if the powers and grounds to the crank sensor and the ign module are good.
Customer: replied 4 years ago.
Thanks for the help. Have a good night
Expert:  Daryl replied 4 years ago.
Thank you
Customer: replied 4 years ago.
I found power at the sensors today. I also discovered something curious. When I disconnected certain wires from the block the ECM case was registering voltage. I was testing the case for ground and the light on my tester came on!!! When I hooked those wires back to the block I got nothing. Is that normal?
Expert:  Daryl replied 4 years ago.
I am not following what you are saying can you better describe what you did?
Customer: replied 4 years ago.
I did all the tests you told me to do for the no spark problem. dunno if you remember
this is what you told me to do:

 

 

1. check the below wires

2. Disconnect the crank sensor and check for power and ground to the sensor on the White/Black and Gray/Red wires.

3. Check the connections at the ignition module for being clean and tight.

4. Verify that the Pink wire at pin P is 12 volts key on and cranking. Verify the ground on pin K Black/White wire, on the ignition module.

Expert:  Daryl replied 4 years ago.

Yes I remember that but I was not following the description you gave above? About the ECM case showed power? Or ground?

Customer: replied 4 years ago.
The ECM showed power. Enough to turn the test light on. When I connected the wires(brown&white and Brown) back to the block then, no light !!!
Expert:  Daryl replied 4 years ago.
Ok that may be normal if that is the ground for the ECM.
Customer: replied 4 years ago.
Ok then is there any other explaination for my problem
Expert:  Daryl replied 4 years ago.
DId you have the power and grounds as described in the test I gave you?
Customer: replied 4 years ago.
the crank sensor had power and ground,the icm had power but the k pin wasnt ground, the ground (which only work when the connector was attatched) was white. The diagram was a little off. Maybe I should pull the harness and start from scratch>
Expert:  Daryl replied 4 years ago.
Maybe Pin K is the problem, it should be ground, I would trace the wire down and see if it is connected to anything.
Customer: replied 4 years ago.
Why would it work before and not now though?
Expert:  Daryl replied 4 years ago.
Maybe the ground wire is broken for some reason.
Customer: replied 4 years ago.
i did notice that the diagram showed only one white wire but I have two
Expert:  Daryl replied 4 years ago.
I show a white wire at E and A
Customer: replied 4 years ago.
can you send me a copy of the schematic you have. I hate these Haynes Books
Expert:  Daryl replied 4 years ago.

My info was actually wrong on the ground being pin K at the module this module grounds through the bracket, below another test and the diagram you asked for.

 

Next, probe the Blue/White trace wire at pin "G". As the engine is turned over by hand, the voltage should toggle high and low as the vanes pass in and out of the crank sensor. Do the same test on pin "H", seeing if it toggles voltage also. If either signal is missing, check the wiring to the crank sensor.

 

graphic

Customer: replied 4 years ago.
Thanks for tellin me because I just verified that I had 13 wires instead of 14. Thanks for the diagram. I also spoke to a mechanic I know and he says check to see if the magnet on the camshaft sprocket fell off. What do you think?
Expert:  Daryl replied 4 years ago.
It is possible for the magnet to fall off but the cam sensor not working will not keep this from running. My daughter actually had a magnet off for over a year and it just started hard but I finally got time to fix it and it starts fine now.
Customer: replied 4 years ago.
My battery died because I left the indicator light on over night so I tested all of the wires going to the crank sensor with a continuity tester to check for consistency and they all passed. I also did the same test to the ecm and to the cam sensor. All of the wires had no breaks.
Expert:  Daryl replied 4 years ago.

DId you ever do the test I described above?

 

Next, probe the Blue/White trace wire at pin "G". As the engine is turned over by hand, the voltage should toggle high and low as the vanes pass in and out of the crank sensor. Do the same test on pin "H", seeing if it toggles voltage also. If either signal is missing, check the wiring to the crank sensor.

Customer: replied 4 years ago.
I did but I got nothing. I checked the wires as stated and they were good. I connected the ICM and checked the connector again and got voltage on three pins
Expert:  Daryl replied 4 years ago.
Ok if the wiring is good maybe the balance/crank pulley is broken and the fins are not moving.
Customer: replied 4 years ago.
I installed a new harmonic balancer that came with the fins
Expert:  Daryl replied 4 years ago.
Your going to need to get the scanner working, if you look at the diagram it shows where all the wires go, check to see if they are all good and ohm them if needed to find the problem.
Customer: replied 4 years ago.
Like I said I traced all the wires from the ICM back to the ECM with a continuity tester and found them to have no breaks. Im still thinking Prom data got erased or damaged when I put in the new ECM.
Expert:  Daryl replied 4 years ago.
The computer will not keep the vehicle from having spark. I would like to know how exactly you did the last test I gave.
Daryl, Shop Owner, Master Mechanic
Category: Buick
Satisfied Customers: 12385
Experience: 28 years experience, Master Mechanic
Daryl and 2 other Buick Specialists are ready to help you
Customer: replied 4 years ago.
Really. I thought the computer sends the signal to the ICM to trigger the spark for the cylinders and it uses the info from the crank and cam sensor to do it efficiently.
Customer: replied 4 years ago.
Anyway I believe I did the tests right. Was I supposed to disconnect the ICM and test from the teminal side or was I supposed to backprobe?
Expert:  Daryl replied 4 years ago.
The crank sensor sends the signal to the ICM to trigger the spark. Back probe or you loose the power to the crank sensor. Let me know the results.
Customer: replied 4 years ago.
ok that make sense cause i got no juice when I disconnected the ICM. I do it tommorrow. Good night
Expert:  Daryl replied 4 years ago.
Ok, good night
Customer: replied 4 years ago.
did the test with a friend twice to verify the outcome. The crank sensor is good. Started at 6.6 v and dropped as we rotated the engine and came back to 6.6v.Tested both wires
Expert:  Daryl replied 4 years ago.

Can you tell me in what order you installed all the new parts? Also do you know if there is pulse at the injectors?

Customer: replied 4 years ago.
When the engine was out I changed the cranksensor. Then when I ran into trouble after installing the engine I changed the ICM and the Coils. After that the Cam sensor and just recently the ECM. I have a PROM on standby that I just recieved today. Yes I believe I hear the injectors.Its a light buzzing noise.Every time I turn over the engine, the fuel pump recharges the lines. I am getting a noid test light to make sure though.
Expert:  Daryl replied 4 years ago.
Great good idea let me know the results.
Customer: replied 4 years ago.
I didnt get the noid light yet but I checked for voltage to the fuel injector with my meter. Am I supposed to get voltage between connection a and b when the ICM is disconnected?
Expert:  Daryl replied 4 years ago.
I would just ground the meter on the battery and the other lead to the power side of the injector connector.
Customer: replied 4 years ago.
I did that to test for voltage on the power side (B) and got 12v. When I tested the connector only (A&B) I also got 12v. I thought the ECM was only supposed to close the ground wire circuit when it recieved the signal and not be closed all the time.
Expert:  Daryl replied 4 years ago.
I do not remember if these are ever toggled on when the engine stops. If there is pulse the condition is probably normal.

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