Getting no A/C voltage from crank sensor when rotating engine

NOMORECHINAJUNK

MEMBER
1996 ACURA TL
135,000 MILES

1996 Acura TL 2.5 no spark. Getting no A/C voltage from crank sensor when rotating engine. Is there supposed to be any DC volts that feed the sensor? Is there a known resistance here? Does the anti-theft kill the ignition system?

The car came to me dead. All the door panels are off. The starter wouldn't engage through key until I installed 2 20 amp fuses in place of the starter cut relay, now it turns over but no spark. Distributor wires and rotor are in working order. No spark from coil. Battery at 12.5 volts.

5 Replies

RIVERMIKERAT

MECHANIC
6,110 POSTS

Do you have power to the distributor? You should replace the fuses with the correct relay. It'll on;y end up being problematic.

We have no capability of seeing the cutoff information. There is no AC voltage in a car. What you see is interrupted DC voltage.

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Friday, February 3rd, 2012 AT 3:05 AM

NOMORECHINAJUNK

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3 POSTS

So, I don't measure the crank sensor signal via the a/c side of a dvom? (Don't alternators produce A/C voltage, hence the name?) Do you know if the crank sensor has a resistance value? How about any resistance values from the other 3 sensors on the end of the cam? Distributor is getting battery voltage with key on, although when I crank it over the test light does not flash, and no flash when turning over by hand. I believe the starter cut-off relay was acting in an anti-theft mode to disallow the starter operation, thats why I did the 2 fuse- bypass. I will replace the fuses with a relay later, just want to get some fire from the spark plugs first. Thanks for the reply.

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Saturday, February 4th, 2012 AT 2:13 AM

RIVERMIKERAT

MECHANIC
6,110 POSTS

Yes, alternators produce AC voltage, but the regulator that is now built into the alternator turns it into DC before it goes anywhere.

No, the signal from the crank sensor is an interrupted DC signal on/off/on/off/on/off/etc.

The test light should flash when the alligator clip is placed on a constant power source and the probe is touched to the negative on the coil.

The relay is simply a high current switch. One set of terminals is the switch, one is where power is applied, the other (used connector) is where the load is. There is also a terminal, 87a, that a load that needs power when the switch is not energized would go. If there is an anti-theft notification, it's from an anti-theft system, not the starter relay.

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Saturday, February 4th, 2012 AT 4:01 AM

NOMORECHINAJUNK

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3 POSTS

So, therefore, no flash means bad crank sensor? BTW, no voltage is reaching the crank sensor on either of its 2 wires. Thanks for the reply.

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Saturday, February 4th, 2012 AT 2:04 PM

RIVERMIKERAT

MECHANIC
6,110 POSTS

No voltage reaching the crank sensor is a bad thing. I have attached the schematics for the engine performance system on your car. #3 contains the crank sensor, listed in the upper left. You need to determine why it isn't receiving power.

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