Reply
Contributor

Re: Cat 3612 LE Misfire and Detonation Isssues

jaredallison26 at gmail.com
Contributor

Re: Cat 3612 LE Misfire and Detonation Isssues

Al,

Are you talking to me?

I suppose I should have addressed Jaredallison in my previous post.
Trusted Contributor
Trusted Contributor

Re: Cat 3612 LE Misfire and Detonation Isssues

I have tried to find a way to send you a G3612 data log but this site does not allow it.  If you will give me your email address, I will be glad to send you a datalog to view.

 

Best Regards,

Al Hunt

Highlighted
Trusted Contributor
Trusted Contributor

Re: Cat 3612 LE Misfire and Detonation Isssues

When the engine is running at or near rated load, any cylinder misfire can cause detonation on the other cylinders as they pick up the load of the misfiring cylinder.  Also the indicated load increases as the misfiring cylinder fuel amount is added to each of the other firing cylinders.  In effect, the calculated load is increased by one more cylinder of fuel usage which causes the ECM to calculate an overload sometimes if the load is near rated . 

Also, high inlet air manifold  temps can cause detonation to occur, especially if the load is high and the fuel btu is high, or if the engine is slightly out of tune.  Add high IMAP to the misfiring issue and the opportunity for detonation to occur increases.  And then if the engine has a coolant leak, then the opportunity for misfire or detonation because of the coolant goes up, increasing the whole detonation issue probability.  It can get very complex when several conditions are present.

 

 

 

Best Regards,

Al Hunt

 

Contributor

Re: Cat 3612 LE Misfire and Detonation Isssues

The Troubleshooter helps some but I have had issues that it did not cover or, at least, I wasn't smart enough to know it did cover it.

 

Just as examples, I have had detonation shutdowns caused by a faulty transformer on a different cyl, a spark plug on a different cyl got a piece of carbon in the gap and shorted the plug. A check valve has caused detonation shutdowns as well.

 

Can you provide a screen shot of exhaust temps, burn times, and secondary voltages or a datalog of the engine running?

 

Are there any other faults or noticable runability issues with the unit?

Trusted Contributor
Trusted Contributor

Re: Cat 3612 LE Misfire and Detonation Isssues

Running with the sensor unplugged from the transducer does not disconnect it from the ECM.  You should replace the sensor and the transducer with the new parts which correct the voltage issue on the ECM output that causes the detonation issue.  This still may not totally solve your detonation problem.  After the jacket water pressure group has been replaced, then you need to go back through ALLthe steps in order in the troubleshooting guide.  Remember that detonation is an event code which means that it is caused by a condition most of the time; it does not mean that a component is usually the cause of the problem.

 

Best Regards,

Al Hunt

Contributor

Re: Cat 3612 LE Misfire and Detonation Isssues

We are running the 276-6793 pressure sensor but two weeks ago we put a buffer in there which basically unplugged the sensor. The panel shows an alarm for the pressure sensor beign unplugged.

 

Even though we did this, we still have detonation issues. So no we did not replace the sensor, we just unplugged it.

Trusted Contributor
Trusted Contributor

Re: Cat 3612 LE Misfire and Detonation Isssues

I always advise techs to follow the step by step procedure in the troubeshooting guide to be sure they don't miss a clue.  But if you have done that, there has been an issue with the jacket water pressure sensor that has caused detonation issues.  This sensor is on the same ECM voltage supply that supplies the detonation sensors.  Cat changed the sensor to solve this problem.  Here is a part of the Engine News text.

Description of Change: The new pressure sensor group is better suited for use with engine coolant.

Adaptable To: The new 449-9665 Pressure Sensor Gp replaces the existing 276-6793 Pressure

 

Sensor Gp only in engine coolant applications. The new pressure sensor is adaptable back to first

production on the serial numbers listed above.

Note: The 449-9665 Pressure Sensor Gp does not replace 276-6793 Pressure Sensor Gp in any

instance other than in engine coolant.

 

There have been quite a few instances in the field where the old pressure sensor (sensor and PWM transducer) has been the cause of detonation. 

 

You might have this issue if you still have the old part number sensor group.

 

Best Regards,

Al Hunt

 

Contributor

Re: Cat 3612 LE Misfire and Detonation Isssues

We fixed the misfire issue but continue to have detonation issues.

 

The gas analysis I sent has a hydrocarbon dewpoint of about -40C so I do not think we are dropping out liquids.

 

Could the detontation be due to lack of grounding? ECM issue? Etc.

Trusted Contributor
Trusted Contributor

Re: Cat 3612 LE Misfire and Detonation Isssues

Thanks for doing this research.  The serial number is not correct for the engine; should be 1YGXXXXX.  The s/n you stated is probably for the A3 ECM module.  The fuel sample looks pretty good and should not be much of a problem if the engine is tuned properly.  With air temps that cold, you want to make sure that the engine fuel supply temp is in the Cat recommended range of 50 deg F to 140 deg F so that hydrocarbon liquids do not drop out.  This will cause detonation also.

 

It sounds like you solved the problem when you made the prechamber coolant leak repair.

 

Best Regards,

Al Hunt