the speed sensor on my girlfriend's sister's 95 civic ex caught fire and melted. some of the wires melted that lead into the wiring harness as well. The car doesn't turn over. I know i need to replace the sensor, as well as figure out a way to splice in the connector wires to the harness, but i'm wondering why it won't turn over. should i replace the entire engine wiring harness? or could the short have caused the ignition coil to fry up as well? or could the wiring harness be screwed and not sending fuel to the injectors? any advice is appreciated. thanks!

 

It cranks but won't start, or it doesn't crank? In the former case check the fuses, after you have the wires clear of each other. In the latter case the engine may be seized, which leads to my next question

Did the whole engine melt down due to severe overheating? Sensors don't just catch fire like that. There would have been an external source of heat. The transmission could have overheated due to lack of oil or slippage if it's automatic.

 

correct, it cranks but won't start. I'll check the fuses. I haven't checked the oil in the transmission. what i was told is that the check engine light came on awhile back, and nothing was checked. the speedometer was acting funky, as well as the odometer, which makes sense that the sensor was failing. Nothing else burned, just the sensor itself and some of the wires leading up to the rest of the wiring harness. I'm thinking of replacing the entire engine wiring harness, since it looks as though splicing in a new connector to the existing harness will be a pain. I'm not so savvy with electrical so I'm not sure if a fire in that part of the harness would disrupt the circuits to other areas of the harness, thereby causing it to not turn over. but perhaps a circuit needs to be complete for that to happen? and since the wires leading to the sensor burned to a crisp, perhaps that's where the issue is with not turning over? thoughts?
thanks in advance!

 

"Turning over" is the action of an engine rotating by mechanical force supplied by the starter; whether or not it subsequently "starts" to run on its own. So that works-- quit saying it "does not turn over". You have a case of "cranks but won't start."

The sensor is powered from a 12 volt circuit that also runs a bunch of other stuff on the engine, including I think the ignition coil. So if the fuse for that whole circuit is blown it will not start. You could turn the key on (do not crank) and probe if the black and yellow wire to the distributor is getting battery voltage. Also watch the lights on the dash. Oil and battery should come on and stay on. Check Engine should come on for 2 seconds and then go out.

 

In that case, it cranks but won't start. I checked all the fuses, all are in tact and not blown. haven't had a chance to probe the wires to the distributor yet. However, the lights on the dash, oil and battery, come on and stay on. Check engine light comes on and also stays on. I feel as though I will need a new wiring harness anyway so I'll probably go ahead and get one off of ebay while i can for a relatively reduced cost. but i'm not certain that replacing the harness and the sensor will fix the not starting issue. guess it'll be one thing at a time.