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Would like a second opinion/confirmation on no start condition.

TJVJR

TJVJR

New member
97 Grand Prix Supercharged ; The car started to occasionally miss and progressed fairly quickly to crank but no start condition. A few miles before it died and wouldn't start back it lost boost pressure at the gauge , It would rev but was misfiring so badly it was hard to tell anything about performance as the idea was to limp the car home ( it didn't make it which makes getting to work on it a bit rough ). It wasn't and hasn't overheated , no loss of oil pressure.The car has several codes - o2 sensor(s) , MAF( replace about a month ago ) , multiple misfire and crank position sensor. I believe the O2 ,misfire & MAF codes are caused by ( secondary problem ) the primary problem which I believe to be the CPS. The car has strong fire at the plugs but after cranking it for some time they never became wet with gas. The fuel pump is running as it should but I believe the injectors aren't firing. From what I understand this car has a dual Crankshaft Position sensor which allows it to continue running ( in limp mode/base map ) when the cps fails. Is this incorrect? A couple of things have me wondering if it is the cps ; It is getting good spark but no fuel so wouldn't that ( the injection system ) get it's input from the cam position sensor? The crank position sensor is covered in oil/gunk from a VC leak , could this be affecting its overall out put? The car is a few miles away but I hope to get to go work on it tomorrow. I plant to start by cleaning and checking the cps and related wiring. It losing boost before dying has me concerned , do you belive this to be a secondary problem ? Any input suggestions will be greatly appreciated.
 


I believe that these only have one CRANK position sensor, and one CAM sensor. If the Crankshaft Position Sensor dies then it will not fire. You can try cleaning the electrical connection to it and see if it fires up. Did you happen to notice if your tach dropped to 0 before it died completely?

You could also try unplugging the MAF and then try starting it. You may need to give it a little gas to help get it started, but it should idle on its own after a bit. If this is the case then the MAF may be shot.

The reason you lost boost is most likely due to the multiple misfires that were occuring. The ECU will pull timing to keep you from getting into boost when it detects issues like this. Keeps you from chipping pistons due to predetonation.
 
Thanks , that makes sense about the boost. The tack did drop to zero a few times right before it shutdown.
 
Should I try cleaning the crank position sensor ( buildup from leaking valve cover ) or replace the crank position sensor?
 


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