Engine Speed Sensor

[SGTLawson]

I just threw my fan belt and took out the wires to my speed sensor. Does anybody know how to fool the computer into thinking that the motor is turning at all times? Would this cause any other problems?

 

[cerberusiam]

The crank sensor tells the computer when to do a lot of its functions. Charging system is controlled by engine rpm, ie over 500 rpms and it will charge. If its an automatic the TPS and speed sensor tie into tell when to shift to overdrive and I believe the trans temp sensor is in there also for protection. Not positive about the speedo but when you lose the computer the speedo quits so it may effect it also. How many of the other functions like grid heater, engine temp, etc are tied in am not sure. Like most computers it will need to have everything working right so your best bet is relace the crank sensor or wires if possible. Good luck.

 

[rkubicki]

The crankshaft speed sensor signal is used by the controller to indicate wether the engine is running or not... In response to this signal being present, the controller grounds the primary coil of the ASD (Auto Shutdown Relay)... . This relay powers the alternator's primary field (which is also switched and grounded by the controller).



Its all part of Chrysler's over-engineered charging system in response to the old-style voltage regulator overheat failures... It would have probably been more reliable to just relocate the original regulator (It was on the firewall over the turbocharger for gosh sake!)



Sorry, if I sound bitter its because I just came back from an 1800-mile haul in which that very charging system was giving me all sorts of problems.



To answer your question, you could ground the primary coil of the ASD and this would effectively bypass the speed sensor. . I don't recommend this... It would be less trouble for you to simply change the sensor.



Rob

 

[BushWakr - RIP]

Keep in mind that the crank sensor needs to have a proper gap setting just like valves.

The sensor should be set when there are none of the balancer notches close to the sensor. It nees a gap between 49 thou. and 51 thou. You must use a non-magnetic feeler gauge to set it too... according to the manual anyway.



The TPS controls 3-4, and 4-3 shift only.

The speed sensor is mounted on the transmission on 727 trannies, and mounted on the transfer case for the A518 trannies if overdrive equipped.



Pastor Bob.

 

[SGTLawson]

Thank you for the reply's. I was on leave and looking for a quick fix. I ended up just soldering new wires on to the sensor. I gapped it with a quarter. Worked fine. In my search for why my alternator wasn't working, I discovered that I am going to need brushes soon. Thanks again.

 

[dpuckett]

FWIW,



The computer can be bypassed and a regular voltage regulator installed. Had it done in my 93. Had I known so many people would find it useful, I'd have drawn a picture of what color wire went to what. CHECK ENGINE light stays on all the time, though. I guess there are some advantages to the older style manual volt regulators. I would not recommend grounding the ASD realy, either- it puts the alt. in a constant charge state.



Daniel