Repair or replace Crankshaft Position Sensor 1999 4runner 2.7L
10-16-2010, 06:09 PM
#1
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Repair or replace Crankshaft Position Sensor 1999 4runner 2.7L
I recently removed and reinstalled my alternator after having it rebuilt. Afterwards, the truck wouldn't start. I cranked it and it kept turning over without running. Oh, what joy. I apparently tore out the wires from my crankshaft position sensor, which was located conveniently behind my alternator, exactly where I was trying to lever the bloody contraption back into place. The Haynes manual makes no mention of the proximity of the alternator to the CPS, and the CPS isn't very visible when you're trying to pry the alternator loose. 
The wires got yanked right out of the sensor itself, which is located directly behind the lower mounting bracket for the alternator. I'll need to remove the alternator mounting bracket to unbolt the CPS. My preliminary price estimate from rockauto is $90ish for a new CPS. For now, I'm PB Blasting those mounting bracket bolts.
In general, would I be better off trying to open up the CPS and re-wire it, or should I just buy the replacement part? I don't know yet how bad it will look once I pull it off.
The wires got yanked right out of the sensor itself, which is located directly behind the lower mounting bracket for the alternator. I'll need to remove the alternator mounting bracket to unbolt the CPS. My preliminary price estimate from rockauto is $90ish for a new CPS. For now, I'm PB Blasting those mounting bracket bolts.
In general, would I be better off trying to open up the CPS and re-wire it, or should I just buy the replacement part? I don't know yet how bad it will look once I pull it off.
10-17-2010, 02:53 PM
#2
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I removed the crankshaft position sensor today. Here's what one looks like if it's not broken:
Mine had the two wires snapped off where they entered the sensor housing. I used a dremel tool and cut back the housing very carefully, to expose more wire. The housing is made up of an eliptical section where the bolts are attached. Going upwards from that (to the right in the image above), there is a square section, then a round rubber cap that the wires emerge from.
In the images below, you can see that I dremeled off part of the case, starting at the base of the square section. All that passes through this part are the two wires (red and white) and a white, hollow box, which I take to be an inert piece of plastic used in the molding process. I carefully exposed the two wires, then stripped back about 3/4" of insulation.
The other end of the wires originally connected to the crankshaft position sensor's connection plug, which is bolted onto the engine a little higher up. I think I'll be able to splice in a section of new wire between the plug and the sensor. I'll show that when I do it.
For this application, what type wire should I use for the splice? I picked up some 20 AWG stranded hookup wire from Radio shack, but it's only rated to 176 degrees Fahrenheit. I think that's the wrong stuff for an application like this, so close to the engine. What kind of wire should I be using?
I also picked up some 60/40 rosin-core solder and a box of heat-shrink tubes. Should those be ok that close to the engine and alternator?
Mine had the two wires snapped off where they entered the sensor housing. I used a dremel tool and cut back the housing very carefully, to expose more wire. The housing is made up of an eliptical section where the bolts are attached. Going upwards from that (to the right in the image above), there is a square section, then a round rubber cap that the wires emerge from.
In the images below, you can see that I dremeled off part of the case, starting at the base of the square section. All that passes through this part are the two wires (red and white) and a white, hollow box, which I take to be an inert piece of plastic used in the molding process. I carefully exposed the two wires, then stripped back about 3/4" of insulation.
The other end of the wires originally connected to the crankshaft position sensor's connection plug, which is bolted onto the engine a little higher up. I think I'll be able to splice in a section of new wire between the plug and the sensor. I'll show that when I do it.
For this application, what type wire should I use for the splice? I picked up some 20 AWG stranded hookup wire from Radio shack, but it's only rated to 176 degrees Fahrenheit. I think that's the wrong stuff for an application like this, so close to the engine. What kind of wire should I be using?
I also picked up some 60/40 rosin-core solder and a box of heat-shrink tubes. Should those be ok that close to the engine and alternator?
10-17-2010, 04:01 PM
#3
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I think you'll be good to go, the internal temps are above 174, but although I'm not 100% sure, I really doubt that the engine compartment tempts are are higher than 174.
Also, you on the side opposite from the exhasut manifold there, so you a bit cooler than the high heat side of your engine compartment.
Plus, FYIW, I have used regular wire to splice wires residing inside engine bays and regular heat shrink tubing with no issues so far.
Also, you on the side opposite from the exhasut manifold there, so you a bit cooler than the high heat side of your engine compartment.
Plus, FYIW, I have used regular wire to splice wires residing inside engine bays and regular heat shrink tubing with no issues so far.
10-17-2010, 05:45 PM
#4
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Reason I asked was that the wiring from the connector plug to the sensor has a rubber jacket with 125 degrees C labeled on it (regular wire packaging says 80 degrees C). This will be right up against the engine.
EDITED:
I've been looking this up online. I'm pretty sure I shouldn't have gotten the standard wire (rated to 80*C or 176*F, so I'll take it back and get some of the 125*C/257*F rated wire as described below)
EDITED:
I've been looking this up online. I'm pretty sure I shouldn't have gotten the standard wire (rated to 80*C or 176*F, so I'll take it back and get some of the 125*C/257*F rated wire as described below)
Automotive Wire Size Calculator Version v1.3
This is a simple calculator for determining the approximate size of a wire based on the lenght of the wire run, and the current for general Automotive use. This can be helpful if doing you own repairs or using a pre-built wiring harness to make sure each circuit is not overloaded. When doing automotive wiring it is important to use the proper wire in the proper place, and this also goes for the operating temps of wire plastic casings, you don't want to run common cheep wire in a hot engine compartment, so make sure that you know the temperature ratings and when important to run higher rated temperature wiring. You may see wires with specs like -
* GPT wire (SAE J1128-GPT) - General Purpose Wire rated -40F to 176F
* SXL (SAE J1128-SXL) - Standard insulation, Automotive Cross-link Wire rated -49F to 257F
* GXL (SAE J1128-GXL) - Thin insulation, Automotive Cross-link Wire rated -49F to 257F
* TXL (SAE J1128-TXL) - Extra thin insulation, Automotive Cross-link Wire rated -49F to 257F
SXL, GXL, and TXL wires are oil, gas, acid and generally chemical proof. One other note about wire type is Teflon and Tefzel are generally very good wire but expensive. And always check the ratings, I have seen Teflon wires with a temp rating of 105C(221F) which is below the typical Cross-linked as indicated above. If your going to get Teflon or Tefzel wire and it's good it will be silver plated conductors and expensive. Typical temperature range for Teflon is -60C to 200C (-76F to 392F) and Tefzel is -70C to 150C (-94 to 302F). Sometime you may see wire called PTFE, PTF for Teflon as well. A few sources exist for Teflon wires, aircraft suppply, surplus somtimes, even a few racing places are starting to sell it.
This is a simple calculator for determining the approximate size of a wire based on the lenght of the wire run, and the current for general Automotive use. This can be helpful if doing you own repairs or using a pre-built wiring harness to make sure each circuit is not overloaded. When doing automotive wiring it is important to use the proper wire in the proper place, and this also goes for the operating temps of wire plastic casings, you don't want to run common cheep wire in a hot engine compartment, so make sure that you know the temperature ratings and when important to run higher rated temperature wiring. You may see wires with specs like -
* GPT wire (SAE J1128-GPT) - General Purpose Wire rated -40F to 176F
* SXL (SAE J1128-SXL) - Standard insulation, Automotive Cross-link Wire rated -49F to 257F
* GXL (SAE J1128-GXL) - Thin insulation, Automotive Cross-link Wire rated -49F to 257F
* TXL (SAE J1128-TXL) - Extra thin insulation, Automotive Cross-link Wire rated -49F to 257F
SXL, GXL, and TXL wires are oil, gas, acid and generally chemical proof. One other note about wire type is Teflon and Tefzel are generally very good wire but expensive. And always check the ratings, I have seen Teflon wires with a temp rating of 105C(221F) which is below the typical Cross-linked as indicated above. If your going to get Teflon or Tefzel wire and it's good it will be silver plated conductors and expensive. Typical temperature range for Teflon is -60C to 200C (-76F to 392F) and Tefzel is -70C to 150C (-94 to 302F). Sometime you may see wire called PTFE, PTF for Teflon as well. A few sources exist for Teflon wires, aircraft suppply, surplus somtimes, even a few racing places are starting to sell it.
Last edited by pendrag; 10-17-2010 at 06:04 PM.
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