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Autotech58, ASE Certified Technician
Category: Car
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Experience:  38 years experience in the automotive repair industry with experience with many makes and models.
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1997 mercury sable wagon cranks but doesnt start

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1997 mercury sable wagon cranks but wont start - I have replaced the CPS, fuel pressure regulator.  When I replaced the CPS, it ran very well for two days..but now will not start at all...



Do you mean Crankshaft Position Sensor (CKP)? or Camshaft Position Sensor (CMP)? I have no clue what a "CPS" is...
Customer: replied 4 years ago.

I replaced the camshaft position sensor....the one there was bad....

and the code reader told me it was too...


OK. So, you did not mention which engine your Sable is equipped with, but MOST Ford engines will run without the Camshaft Position Sensor. You can unplug it and the engine will still run. It will not run correctly, but it will still start and run. The CMP is only used to synchronize the injectors. Without it, the Powertrain Control Module (PCM) will simply "Bank-Fire" the injectors.


So, what is your code reader telling you now? (Code NUMBERS would be very helpful)

Customer: replied 4 years ago.

I have not tried to start with the camshaft position sensor unplugged. As you know, it is a real pain to get to...with removing the throttle body, and moving the wire harness which exactly on top of it.....


The weird thing is...if I try to start starting fluid in the throttle body, it will not start. Also, if i check for fuel in the fuel rail with the fitting, plenty of fuel squirts out of the rail. I can hear the fuel pump working...

I wasn't telling you to try to start it with the CMP unplugged. I was telling you that so you would understand that the CMP is not the reason your engine is not starting because the engine will run even if the CMP is unplugged. And NO, I do not know what a pain it is to get to because you still have not told me which engine we are talking about. However, I am assuming at this point that we are talking about the 3.0L VIN code 'U" engine, not the dual overhead cam 3.0L...???


It sounds like it is not a fuel delivery or fuel injection problem. Which brings me back to my last question.....


What is your code reader telling you now?

Customer: replied 4 years ago.

It is the U VIN code engine. The code reader is saying no codes....I have tried to read several times and no code is displayed.



OK, does your OBD tester also read live data? or does it just read codes?
Customer: replied 4 years ago.

it is an actron autoscanner CP9575 which can read live data

That's great! That will help this project a lot.


Go into the live data and look at the RPM PID while you are cranking the engine over. Does the data show that there is an RPM reading? (not just "0")



Customer: replied 4 years ago.

I tried it twice...shows the RPM reading at 0 both times....

Then the problem is going to be one of three things:


(1) A faulty Crankshaft Position Sensor (CKP)


(2) Bad wiring between the CKP and the PCM


(3) Something else is shorting out the Reference Voltage (VREF) circuits to the PCM and the CKP cannot work because of that.


Now, I will give you the choice:


You can either try a CKP sensor (The most likely cause)




I can send you the diagnostic test routine for "No-Start" from the service manual if you think you can follow it to actually diagnose the problem before buying any parts.


Please note that I am giving you this choice because I do not know your skill level or if you know how to follow a diagnostic chart unless you tell me.

Customer: replied 4 years ago.

Well I am no pro...but replacing the crankshaft position sensor shouldnt be that hard. Can you assist me in locating it on the engine?


I can buy it tomorrow and most likely try to replace it on Sat or Sun.


It is not that expensive..about $24....



It is on the front of the engine just behind the pulley for the serpentine belt on the crankshaft. Stand by for a few, and I will get you a diagram.
Customer: replied 4 years ago.


Here it is.


Please download the PDF file HERE


Please note that the file at the link above will be deleted in a few days due to copyright restrictions


Also note that the instructions do not tell you, but it is my experience that this job is much easier to do if you raise and support the vehicle, remove the right front wheel, remove the right splash shield, and work through the wheelhouse opening.


I hope this does the trick for you.



Also note that you can always come back and post any "follow-ups" that you may have AT NO EXTRA CHARGE even if you have "Accepted" my answer or "Rated" my answer. This applies to any further questions you may have about issues that are directly related to the subject on this thread, or if you just want to post a reply later to let me know how things went (I always appreciate thoseLaughing).


-Dave (Autotech58)

Customer: replied 4 years ago.

Excellent...I will replace this sensor and see if that fixes it. Thanks alot...and I will let you know if this does the trick. I will certainly return for more questions if the car still does not start.



If it doesn't then I will have to send you the diagnostic charts anyway - simply because there are many other things that can cause you to lose your crank sensor signal - all of the possibilities will have to be checked.


Good luck!

Autotech58 and 7 other Car Specialists are ready to help you
Customer: replied 4 years ago.

Ok...checked the wiring to the crankshaft position sensor...when I was locating it..and tried to start car and it started. Now code reader can read the RPM. Now drives fine..but oil light is on. I checked the oil and it is not low...but runs fine.


I read the codes and no codes are present.


Any suggestions?



It is hard to say. If you moved the wiring around, it is very likely to be a loose-fitting connector or a break in the wiring inside the wiring harness that once again made contact when you moved the harness around. It can be difficult to do with that vehicle, but this is where a "wiggle test" comes into play. I usually use a "hook" made out of coat hanger to wiggle the harness around with the engine running to see if I can get it to stall. I have even been known to do this with the serpentine belt removed (for only short periods of time to prevent other problems like over-heating) because it is "safer" and makes getting to the harness considerably easier.


The crank sensors themselves can also be very "intermittent" it is very common for them to start right up and run when they are cold and then shut down and refuse to restart after the engine warms up. Then you let them set overnight and the thing starts up immediately when the key is twisted the next morning. Intermittent problems can be very difficult to diagnose. It often requires disassembly of the wiring harnesses to locate breaks in the wires, etc..


For the oil light thing, I can only tell you to check the wiring and connector to the oil pressure sending unit. There is a good chance that if there is a wiring issue, you might find out what was wrong with your crank sensor signal at the same location in the harness.


Otherwise, you will have to check the actual oil pressure with a manual gauge and determine if the sending unit is "lying".

Customer: replied 4 years ago.

Where is the oil pressure sending unit? Can you send a diagram?


Is it close to the Crankshaft position sensor area?





Technically, that is a completely separate issue from the one originally posted on this thread. However. you can get a diagram of the oil sending unit HERE


It is located at the rear of the engine just behind the right cylinder head. (The head closest to the windshield).


Bonuses greatly appreciatedLaughing


-Dave (Autotech58)

Customer: replied 4 years ago.

Excellent..that did it. I found the sending unit by feeling up under the throttle body..and the connector was not on very good. When I pushed it on further...and started up the car, the oil light went off. Thanks..



Cool! I like to help whenever I get a chance.