420a Crank Sensor

[lsotto_2005]

What could be the cause of reading a constant 5V from the Crank sensor signal wire?

I am measuring it at the ECU. I checked continuity and its the same reading through the whole cable.

There is no apparent volt switching when I manually rotate the engine. When the fuel pump prime it goes to 5.02v then after priming it goes back to 5v no matter how many time I rotate the engine, it does the same thing.

The sensor is new.

I cant get my car to start, it cranks but wont start. Could this be ECU? I swapped with another one I have here and the same thing happens.

 

[sillycon]

Do you have any way of logging when cranking to see if the ECU is getting a crank/cam signal (e.g. RPM)?

I'm not familiar with the 420 setup, but if it has a cam sensor, could you try wiring the cam sensor signal into the crank sensor signal (similar to the 1g in a 2g situation)? If so, and the car then starts, you'll know the crank sensor is bad.

 

[VelocitàPaola]

Do you have any way of logging when cranking to see if the ECU is getting a crank/cam signal (e.g. RPM)?

I'm not familiar with the 420 setup, but if it has a cam sensor, could you try wiring the cam sensor signal into the crank sensor signal (similar to the 1g in a 2g situation)? If so, and the car then starts, you'll know the crank sensor is bad.

I'd put my money on a bad or incorrectly installed sensor too, but wiring the cam sensor into the crank sensor's wire won't work: the crank has a special tooth pattern, so the ECU won't even sync with the cam signal.

 

[sillycon]

One more thought: perhaps there's a bit too much runout on the thrust bearing?

I realize it's a 420 and not a 7b 4g63, but ANY engine can develop excessive runout of the thrust (e.g. crank walk).

 

[lsotto_2005]

Could it be that the "new" sensor that I purchased was bad? What are the possibilities of such bad luck jeje.

I check, re checked and double checked that the wiring was correct. Im getting a full 8-9v on the yellow wire, the ground, well its ground and the constant 5v on the blue and white one.

Question, If I unplug the pigtail and meassure the blue/white cable, shoulf I get 5v? or 0v? Cause if I disconnect it, I get 5v along with the other readings.

Do you have any way of logging when cranking to see if the ECU is getting a crank/cam signal (e.g. RPM)?

Nope, no way of logging. I have Factory ECU. The best way I have to see if its working is turning the engine manually and reading the voltage directly from the crank sensor.

Another thing, If I do the process of turning the engine manually and reading the voltage on the CAM sensor, it does the 0-5-0-5v switching that its supposed to.

You can mark this one as solved!

-Paul hit on the nail. I had checked the wiring, and it was in place, but apparently the soldering had broken off behind the tape so I could see it wasn't making contact.

So after unhooking, again, all the wiring and redoing it with patience, I finished, connected everything and rested to make sure it was switching and it was. Getting a solid 5v and then a good 0v while hand turning the engine.

For future reference, anyone with a no spark problem, but the fuel pump primes, start at the crank sensor and work your way up to the ECM. A solid way to figure if the sensor is working is to manually turn the engine over and measure the voltage with a DMM on the blue/white signal wire. If the voltage alternates between 5v and 0v you can discard the Crank sensor from possible problems.

Also, ASD relay is a pain so dont forget to check that one as well.

Thanks all for your help and Input. Gotta love these cars to bang you head against the wall and still love driving them! jaja

 

[VelocitàPaola]

Thanks for reporting back with the solution.