A week ago I posted this testing rpm sensor 200

1991 240
Some of the time the car will not start (it will crank) I got a 2-1-4 fault code on #6 .The contacts on the rpm at the firewall look very clean .The shielding is cracked in some places , but the wiring looks good . I tested the wire from the rpm sensor with a meter and got 176.4 oms .

Well, EdM. of Franklin, MA posted this :

The thing is a pickup, like on a guitar. The wires don't carry current; they carry an electromagnetic signal to the ignition control unit. The blue foil you see under the insulation is shielding against interference in that signal. If you can see the wires inside the shielding, that means the shielding is broken. See, if you have wires carrying current, and the insulation breaks, shorting is the problem. If you wanted to try a simple experiment to demonstrate why broken shielding is a problem in wires carrying a signal, go to a local music store and ask if they will let you hook up an electric guitar to an amplifier using a speaker cable (unshielded) in stead of a patch cable (shielded). This experiment will be especially effective if they have fluorescent lights which put out a lovely 60-cycle electromagnetic wave, giving you a lovely low B-flat added to whatever other sound comes out of the amplifier. That said, you don't want all of the EM waves coming out of other parts of your ignition system (especially the plugs and wires) to be picked up by your rev sensor.


Sound good to me :

So, I was think that the sensor pick up is good but the wires is bad. RIGHT ?
I wanted to do A little test . What I did was use a little bit of aluminum foil for electromagnetic signal shielding and the good old electrical black tape and wraped it up. I was also thinking that the wire was touching the engine and maybe that was a soure of EM waves coming out of other parts of your ignition system (especially the plugs and wires) to be picked up by your rev sensor like EdM said .I then ran the wire along the firewall away from the engine.

Well,. I started the car and drove it for two days. Not one no start and no more codes.

I did order a new rpm sensor and put in, about a 35min. job (thanks brick board for all the tips )

I looked at the old sensor now it was out and had a little light tan color rust on the little metal pick up. I cleaned it with a soft metal brush.

Here is the BIG ????? If I had put this old sensor back in would it be a fix. I would try it out, but I'm driving out east on TUE. Did someone try this before ?
I'm sure someone was here .
Looking forward to your responses.

P.S. I will test the wire soon and see if it is 200 to 500 oms like Chiltons book said it should be or around 176.4 oms as it was on the old sensor.




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