Faulty CKP Sensor?

[wellcraft34]

From the neutral switch there’s the yellow/green stripe wire and black/blue strip. With key on the black/blue is hot back to the black rectangle “relay” that sits beside the ECU. From there the black/green stripe is hot back to the black plug tucked behind ECU. I’ve happened across a lightly used complete engine harness. Are you thinking there may be an issue somewhere in the harness by chance?

[redlowrey]

Ok we are starting to get some direction, I think something is going where it shouldn't, this is why I wanted you to test the crank sensor disconnected from the loom. Three volts on your multimeter while cranking would be rms voltage, so peak to peak when measuring off an oscilloscope would be higher so that looks alright.. Not having a wiring schematic for your engine makes it a bit harder, All the wiring diagrams I have only show two wires brown to the neutral switch and then yellow and green to the starter relay. Has your old loom got these extra plugs are the wiring colors the same.

Something is not adding up here, when you turn the key to the start pos you should have battery voltage traveling down a brown wire to a joint connector junction, where it splices and sends battery voltage to the ecu to tell it the engine is being cranked and to the neutral switch, and if the switch is closed through the yellow and green wire to the starter relay. The only relay that used to be beside the ecu was the power trim relay and the ecm main and starter relay tucked in behind it. Can you send some photos of the relays and wiring. Can you disconnect the other plugs so that only the yellow and green wire at the starter relay is hot when turned to the start position. I will buy a cd on line they are only 15 bucks then I will be able to see what is going on.

[wellcraft34]

The burnt pin is ECM ground, no wiring or plugs under the cowlings has been changed out. I did replace some ground wires but that’s it

[wellcraft34]

ECU harness

[wellcraft34]

More harness

[wellcraft34]

Have a friend sending me a replacement engine harness to try out.

[redlowrey]

Ok your engines computer has full control over the starter motor, when you turn the key to the start position battery voltage via the brown wire will go to the ecm, not directly to the neutral switch as previous models.
The ecu will send battery voltage via the neutral switch and keep the starter relay grounded for up to four seconds after you let go of the key, so unless your problem with the key switch kept it cranking there might not have been one. That little black box in the picture are the wires going to it black, white, black and blue, black and green, if so that is a capacitor.

Go back to the crank sensor plug and follow the black and white wire to a multipole joint connector with about eighteen wires coming of it, black and white, black and green, white, gray, and black, test the crank sensor there and see if you still have good voltage, their might be some corrosion there , and that may have been the original problem. If it is good there test it at the ecu.

[wellcraft34]

So I found a loaner engine harness, installed it this morning with the same result, no spark.

[wellcraft34]

The only thing I can think of is if the starter isn’t spinning the engine over fast enough? To me, it sounds fast enough, but I’m at a loss??

[redlowrey]

Check the crank sensor at the joint connector like I said if the compuror can’t read the crank signal you will never have spark

[wellcraft34]

Check the crank sensor at the joint connector like I said if the compuror can’t read the crank signal you will never have spark

I know the connector, could you please elaborate where/how to test here? It was ac V right?
,

[redlowrey]

We need to get a good crank signal at the computer, when you tested the sensor unplugged you got 3 volts ac not milli volts is this right, go to the joint connector and all the black and white wires are sensor grounds for various sensors including the crank sensor, one of the black and white wires goes to the computer. Have a look at the joint connector and do a voltage drop test on each one with your multimeter
on milli volts black to a good ground and red to each one with the engine cranking, note what the readings are.
The crank sensor ground goes from the terminal block to the computer find it, do a voltage drop test there, if ok find the red and black signal wire might be at the bottom of one of the ecu plugs connect up your multimeter on ac black to the black and white ground at the ecu, red to signal wire red and black crank it over and note the readings. Look for any black wires at the computer and do a voltage drop test on it.
also there looks like there is a few black wires going to ground near the starter.
Remember when you do a voltage drop test on a ground, the circuit needs to be loaded.


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[wellcraft34]

Ok, I tested all of the black/white wires at the terminal. On those I believe the # was 4 dropping to 2. The CKP ground to EVU was same, the red/black CKP at ECU was about 3V. I did all of this while cranking. What I can’t figure out is I replaced the whole engine harness to eliminate the burnt ECU plug and a ton of corrosion in the harness and the issue remained.

[redlowrey]

I don’t follow what you mean 4 volts down to two what do you mean by the hash

[wellcraft34]

I don’t follow what you mean 4 volts down to two what do you mean by the hash

Number, “the number was”