What is a crank sensor?

my 1985 toyota corolla has 213,000 miles. It occasionally is reluctant to start. My mechanic says it needs a crank sensor, about $2-300. It attempts to crank every time and it sounds like it is not getting gas. It worked perfectly for awhile after adding a can of dry gas. The problem seems to occur in dampness (rain, parking on a wet gravel driveway, slushy snow).

Any ideas would be greatly appreciated. I love this car!!

just search the internet for answers…eg.

It’s a crankshaft position sensor, and it does exactly what you’d think. It tells the computer what position the crankshaft is in.

Difficulty starting in damp conditions is often caused by old, dried-out spark plug wires. How old are your wires?

What leads your mechanic to say that you need a crank sensor? What has been done to try to address this problem?

The fact that the problem comes with dampness suggests to me some kind of wiring problem - sensors themselves can be affected by water, but I’d look at the sensor’s wiring and harness before even thinking about a new one.

Actually, the first thing I’d do is change the spark plug wires and check out the rest of the ignition system - and I’d do all of that long before thinking about a crank sensor.

From what I have read this engine has a distributor with the spark timing sensor inside – i.e. no crank position sensor. If this sensor has a problem, most times the distributor is replaced with a new or rebuilt unit which may come to the $2-300 cost range. If this is the original distributor with this much mileage on it, it might have bushing problems allowing the sensor gap to wander leading to misfiring and starting problems.

But, as others have said, this problem is most likely due to current leakage in the high voltage part of the system. When did you last replace the spark plugs, the spark plug wires, the cap, and rotor. If these have been replaced recently, make sure that the ignition coil high voltage tower is dry and clean if external or clean if internal to the distributor.

Get back to us with the recent history of your maintenance and we can go from there…

Your 1985 Corolla doesn’t have a crank sensor in the normal sense. Instead there’s a magnetic pickup and reluctor wheel in the distributor assembly. And if this is the problem, I can’t see how changing magnetic pickup in the distributor could cost $200.00-$300.00. You need to find a new mechanic who won’t rip you off.


Thanks to all for the input. And I apologize for my big OOPS. The car is 1995, not 1985. My stupid pill must have kicked in.

Okay 1995 Corolla. Gas and brake lines replaced in 2009, starting to rust out(really 2009), my mechanic said the gas tank was good and the fuel pump was fine. The battery is 2008. New tires; new radiator in 2008 due to mva. Starts best in dry sunny days. Starts worst in cold and wet, sometimes if I wait ten minutes in between attempts, it starts on the 3rd or 4th attempt.

BTW, I have been dealing with this garage for 20 years and the two men and one lady are god’s gift to car owners. They have worked on my 1985 F-150, 1998 Ranger, 1993 Capri and the Corolla. Did I mention it is a 1995 Corolla?

Thanks again

Thanks, Tester. My error. I should have written 1995 and not 1985. The spark plug wires look pretty good but since other replies suggested changing them, I’ll start there. The gas and brake lines were replaced in 2009; the gas tank and fuel pump are good. Got a new radiator in 2008. Someone suggested that I spray everything down with WD-40 to remove moisture. Anybody ever hear of that?

Yes. It would be a very temporary fix that you might use to verify the [faulty wire] diagnosis.

The OEM crankshaft position sensor for your car lists for $115 and sells on line for $85. If you didn’t know what it was, you probably should pay someone to install it for you, so the cost should be in the $200 range. If the car won’t start when it is damp, it is possible that the insulation on the sensor or lead is old and cracked, letting in moisture. This is a very low voltage signal, so the insulation and shielding has to be intact.

This is what a redneck,country person would do.
Seeing you have a car with a lot of miles,play in dist,old wires,lower compression,valves off and wore.
Drill a little hole in intake close to throttle body and get a good can of starting fluid with straw. If you are alone roll dn window and put key in,peel back duct tape covering hole and give it a shot of fluid. Reach in and start car and put tape over hole. After you do it a few times you will know how much to use,
If someone is with you have then turn key.
Keep fluid in a bag or pouch out of the sun.
Hey it works LOL

to add, the crankshaft position sensor records how fast the crankshaft is rotating… There is something that add to the information with comes from the control ignition timing. Now that’s too technical, anyway that tiny sensor is needed to calculate the engine speed. If you see that something is off, check it immediately with your mechanic. Or even auto parts online would have a great advice for that.