CPS output characteristics

[avizpls]

I am having a problem with my 92 Lumina 3.1L . There is fuel, no spark.

I have a feeling that the culprit may be the CPS. what should the output look like during cranking? its an AC voltage, but what voltage, and what frequency?

Also, will there be spark even if the coil module was disconnected from the ECU? i.e. only having the power and CPS hooked up? I want to rule out the ECU as being the source.


Thanks all

[tru2chevy]

I was just about to ask a similar question....

My car ('91 Lumina 3.1) ran great on Saturday, and when I went out on Sunday to start her up, she just wouldn't start. Cranks fine, and there's fuel pressure in the rail, but no spark. ICM and coilpacks were replaced approx. 3k miles ago, CPS is original with 197,xxx miles on it.

It seems like it would be easy to just replace the CPS and go from there, but if there is a way to test it I would like to do that first.....I don't have much money to throw into this car.

Thanks for the help in advance.

- Justin

[Superdave]

the CPS is cheap as hell.. i'd replace it just for good measure anyways.

but yes it's a digital square wave output, i don't remember the voltage because i had my Oscope on it last time but it's probably less or around 5V

and no, you won't get spark if the ECM is disconnected.

[ryan.hess]

I am having a problem with my 92 Lumina 3.1L . There is fuel, no spark.

I have a feeling that the culprit may be the CPS. what should the output look like during cranking? its an AC voltage, but what voltage, and what frequency?

Also, will there be spark even if the coil module was disconnected from the ECU? i.e. only having the power and CPS hooked up? I want to rule out the ECU as being the source.


Thanks all

If you're getting fuel, then the CPS can't be the problem. The ECM only injects fuel when it sees the crank is moving - via the crank sensor and ignition module.

Yes, there will be spark if the DIS module is connected to the crank trigger and power. It will be "default" advance - 10* BTDC, IIRC.

[tru2chevy]

the CPS is cheap as hell.. i'd replace it just for good measure anyways.

Autozone and Advanced Auto Parts both had them listed for $80-$90. Compared to a new ICM, this is cheap, but I'd still rather not spend the cash if I don't have to.

- Justin

[avizpls]

thank you all for the input!

Autozone and Advanced Auto Parts both had them listed for $80-$90. Compared to a new ICM, this is cheap, but I'd still rather not spend the cash if I don't have to.

I just purchased a CPS at Advance for $18.48 +tax

A Distrubuterless Ignition System module is $88.xx +tax.

If you're getting fuel, then the CPS can't be the problem. The ECM only injects fuel when it sees the crank is moving - via the crank sensor and ignition module.

"Getting fuel" may be a misrepresentation. My fuel rail is pressurized. Whether the injectors are firing or not, I do not currently know.

[Superdave]

I was gonna say.. a CPS is under $20 unless you're in Canada

[tru2chevy]

I just purchased a CPS at Advance for $18.48 +tax

A Distrubuterless Ignition System module is $88.xx +tax.

Wow....maybe I was reading something wrong then when looking for the crank sensor.

"Getting fuel" may be a misrepresentation. My fuel rail is pressurized. Whether the injectors are firing or not, I do not currently know.

Yea, I'm in the same boat. Haven't checked to see if the injectors are firing, I just know that the rail has pressure.

- Justin

[avizpls]

Someone told me that there is a knock sensor, and if the magnet that is on the cam falls off, it will fail to read, and not allow spark.

Is this true? Does the car even have a knock sensor? I could wait to get to the car (which is currently 3 hours away, awaiting my truck and trailer) and read the manual, but I want to develop as much of a game plan as possible for repair.

Thanks again all.

and tru2chevy, if I solve this problem, Ill be sure to let you know the results. Maybe yours is the same issue?

[tru2chevy]

and tru2chevy, if I solve this problem, Ill be sure to let you know the results. Maybe yours is the same issue?

It does sound like it could be the same issue. I'm prolly just gonna pick up a sensor after work today and then have AAA tow my car to my dad's service station so I can toss it on the lift and replace it without laying on the ground on the street in front of my house.

Good luck with yours!

- Justin

[IsaacHayes]

CPS (crank position sensor) You want the skinny tube looking one that goes into the oil pan, not the one on the side of the pulley (I think only 3100 has this though).

DO NOT get a $11 autozone one. It failed me in less than a year.
Go to O-riellys/etc and get at least a borg warner one, should be $20 something dollars.

I've replaced lots of $$ spark related components, and its always came back down to the CPS. Swapped the old ICM/etc back on and still runs fine, so I know it was the CPS.

197,000 miles is a lot for a CPS. That is the only electronic part on my car that has ever failed. Replace it.

[ryan.hess]

"Getting fuel" may be a misrepresentation. My fuel rail is pressurized. Whether the injectors are firing or not, I do not currently know.

Okay. The fuel rail is pressurized on key on, so if you don't know that your injectors are firing, might as well replace it...

[avizpls]

Well, you should be suprised to hear that I broke it off and can't get the SOB out f the block.

Any thoughts on how to do so in the easiest manner?

[ryan.hess]

Do you own, or have access to a firearm?

[RebelGT]

lol, thats a funny question to ask this particular person, ha ha.