car still wont start

Subject: car still wont start Sat Nov 24, 2012 12:02 pm

i have a 97 buick riviera i recently changed the crank shaft position sensor it cranks over but still wont start what could the problem be?

Subject: Re: car still wont start Sat Nov 24, 2012 12:27 pm

Has there been any SES lamp or other codes? If so, you may need to perform a CASE learn procedure. Having said that, I've never done one, even after removing the engine for rebuild. Still, it's easy to do, just in case.

_________________
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Subject: Re: car still wont start Sat Nov 24, 2012 1:50 pm

dartcars wrote:: i have a 97 buick riviera i recently changed the crank shaft position sensor it cranks over but still wont start what could the problem be?

Find out what the engine is missing, fuel, air, spark. Check for a spark at a plug wire. Check the fuel pressure.

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98 Riviera SC3800 All stock except gutted air box.
1970 Buick GS455 Stage1, TSP built 470BBB, 602HP/589TQ
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Subject: Re: car still wont start Sat Nov 24, 2012 3:42 pm

Has the car ran since changing the crank sensor? If not, was no start your reason for changing it?

Subject: Re: car still wont start Sat Nov 24, 2012 11:26 pm

dartcars wrote:: i have a 97 buick riviera i recently changed the crank shaft position sensor it cranks over but still wont start what could the problem be?

Quickest way to diagnose is with a Tech II or equivalent.

- check if the fuel pump is working, command it on and check pressure
--telltale, turn the switch to ON position, see if you can hear the fuel pump run to prime the ignition -- it does that as part of the start sequence
- check for spark (can use a dummy plug DO NOT RUN THE COILS w/o PLUGS OR DUMMIES)
- check for air, starting with the air filter (how clean), the air flow sensor (is it plugged in) the throttle body (clean screen).
- check if you are getting a crank sensor and a cam sensor signal
- check if the security system is working ok (SECURITY light goes out while cranking)

Albertj

Subject: Re: car still wont start Sun Nov 25, 2012 7:57 am

dartcars wrote:: i have a 97 buick riviera i recently changed the crank shaft position sensor it cranks over but still wont start what could the problem be?

bigdave wrote:: Has the car ran since changing the crank sensor? If not, was no start your reason for changing it?

I agree, why did you replace the CPS, and did it run after changing it?

There have been others with wiring harness issues where the wire from the sensor became brittle and broke next to the firewall connection of the engine harness. It's worth checking wire resistance on the CPS wiring back to the PCM. You can also have someone tug gently on the harness here and there while you are cranking to see if it suddenly fires up. If that works, you have a broken wire somewhere... but that may not work either.

Subject: Re: car still wont start Sun Nov 25, 2012 7:39 pm

deekster_caddy wrote:

dartcars wrote:: i have a 97 buick riviera i recently changed the crank shaft position sensor it cranks over but still wont start what could the problem be?

bigdave wrote:: Has the car ran since changing the crank sensor? If not, was no start your reason for changing it?

I agree, why did you replace the CPS, and did it run after changing it?

There have been others with wiring harness issues where the wire from the sensor became brittle and broke next to the firewall connection of the engine harness. It's worth checking wire resistance on the CPS wiring back to the PCM. You can also have someone tug gently on the harness here and there while you are cranking to see if it suddenly fires up. If that works, you have a broken wire somewhere... but that may not work either.

I forgot all about this --- check the big harness connector a t the firewall for an intermittent open especially in the wires on the corners of the big plugs.