CPS failure

[NickInTimeFilms]

15 hours ago, Eagle_SX4 said:

@NickInTimeFilms do you have any suggestions. Is there any reason other than a faulty CPS that the "CPS Crank fault" error would pop up on the R.E.M.?

For all the info available from the ECU, it's rather lacking when it comes to anything directly involved with the CPS.

 

The REM is starting from the end, rather then the beginning of the chain so it's still difficult to pinpoint the CPS for sure.

 

All that code really tells you is that the ECU is not sending a spark command to the ICM, but this could be caused from multiple reasons, not just dead CPS. Knowing exactly why the ECU isn't deciding to send spark has still been a mystery to me beyond a weak CPS signal so it's just written like that for now.

 

 

[Eagle_SX4]

56 minutes ago, NickInTimeFilms said:

For all the info available from the ECU, it's rather lacking when it comes to anything directly involved with the CPS.

 

The REM is starting from the end, rather then the beginning of the chain so it's still difficult to pinpoint the CPS for sure.

 

All that code really tells you is that the ECU is not sending a spark command to the ICM, but this could be caused from multiple reasons, not just dead CPS. Knowing exactly why the ECU isn't deciding to send spark has still been a mystery to me beyond a weak CPS signal so it's just written like that for now.

 

 

Thanks for the reply I am going to check all my grounds today and will report back.

[eaglescout526]

What if the CPS is fine and it’s the coil or ICM? Based on what nickintime said, the REM is reading at the end of the problem vs where it is and the ECU is sending the spark signal but the ICM isn’t communicating back or sparking to fire off. 
 

The coil and ICM are absolutely fine? That was the next thing I tried when my XJ died on me after I tested the CPS to be fine. 

[Eagle_SX4]

13 minutes ago, eaglescout526 said:

 

The coil and ICM are absolutely fine? That was the next thing I tried when my XJ died on me after I tested the CPS to be fine.

I honestly don't know if my coil or ICM are good. That is something I can test but I don't have a spare to swap out. Test procedures for those would be much appreciated.

[NickInTimeFilms]

16 minutes ago, eaglescout526 said:

What if the CPS is fine and it’s the coil or ICM? Based on what nickintime said, the REM is reading at the end of the problem vs where it is and the ECU is sending the spark signal but the ICM isn’t communicating back or sparking to fire off. 

 

To dive a little deeper, the ECU reports the time gap between spark commands, which through some math we can find the engine RPM from. If there is an RPM reading to show, that means the ECU is sending spark. No RPM, No spark commands.

 

So if you are getting an RPM reading but no spark, then I would look into the ICM, coil, or distributor and plugs.

 

The thing to take away is that RPM isn't a direct reading from the CPS, but rather the aftermath of the ECU processing the CPS and giving the ok to send spark.

 

I wish the ECU atleast sent an OK flag when CPS signal is sufficient, but they really dropped the ball in that area of reporting.

[eaglescout526]

4 minutes ago, NickInTimeFilms said:

The thing to take away is that RPM isn't a direct reading from the CPS, but rather the aftermath of the ECU processing the CPS and giving the ok to send spark.

I’ve completely forgotten about this little detail. That’s usually how I know something is wrong if I don’t see the tach bouncing. 
 

11 minutes ago, Eagle_SX4 said:

I honestly don't know if my coil or ICM are good. That is something I can test but I don't have a spare to swap out. Test procedures for those would be much appreciated.

I’ll look in my MPFI manual and see if there is something. 

[Eagle_SX4]

29 minutes ago, NickInTimeFilms said:

So if you are getting an RPM reading but no spark, then I would look into the ICM, coil, or distributor and plugs.

 

The thing to take away is that RPM isn't a direct reading from the CPS, but rather the aftermath of the ECU processing the CPS and giving the ok to send spark.

I am not getting any rpm reding on the REM or my tach. 

[Eagle_SX4]

@Ωhm just checked and the white with trace wire (D1) on the CPS connector is the sensor ground while the key is on. There is no connection to ground with the key off.

[eaglescout526]

MPI manual is very useless on the coil…

[Eagle_SX4]

I refreshed the grounds and it still won't start

[Eagle_SX4]

Checked for spark with a spark tester and I do have spark. But it still won't start. I have fuel at the rail but don't have a pressure gauge.

 

What is perplexing is that the rem still has the "CPS Crank fault" error. I am now going to pull my fuel pump and see if the hose has come undone. 

 

[Eagle_SX4]

It now runs. I don't know what fixed it but it runs. I reindexed the distributor and now it runs. I don't know what ended up being the issue. I think there were several things wrong all at once and I had to fix every one without knowing if it was fixed until everything was fixed together.

[eaglescout526]

Gotta love Renix. It puts you through your paces, tests your wits and even pulls some hair until it just runs. 

[Eagle_SX4]

This all started because of a failed cam gear and still not sure why it failed. Just checked my oil pressure with a mechanical gauge and during cold idle it is at 50 psi. 

[NickInTimeFilms]

13 hours ago, Eagle_SX4 said:

This all started because of a failed cam gear

This makes me wonder if your engine would have tried to start if you unplugged the distributor sync sensor before the re-index.

 

Maybe if the ECU can't match the cam to crank then it won't attempt to fire. I may suggest this in the future for troubleshooting.

[Eagle_SX4]

2 minutes ago, NickInTimeFilms said:

This makes me wonder if your engine would have tried to start if you unplugged the distributor sync sensor before the re-index.

 

Maybe if the ECU can't match the cam to crank then it won't attempt to fire. I may suggest this in the future for troubleshooting.

Funny you mention that the first time I got it to run the distributor was unplugged and the sync sensor error code popped up on the REM but it was running. I shut it off and plugged it in and it didn't make much difference in how it ran.