New member

Re: Caterpillar C9 Problem

good afternoon, i have a similar problem;  I am ETO aboard a ship in Mexico, has an emergency generator / harbor Caterpillar C9 few months that has a fault does, and that is when we put it in service harbor mode, sometimes it works well for days but sometimes suddenly lower the speed and frequency and causes the blackout, and was change the fuel pump, the harness of injectors, motorized potentiometer E7800 and Converter (PWM), including timing and speed sensor synchronizer relay coming.

some brainstorming appreciate that they can give me another perspective.

best regards

Trusted Contributor

Re: Caterpillar C9 Problem

First off all, Engine Derates are NEVER allowed by any classification Buearau on generator sets, because of the very simple fact.


if a derate occures you get a reverse power trip. if the system is not fast enough it might trip the wrong generator, and causes you a complete black out.


solution of this problems is very simple.


the contacts in the relays of the Key switch and run stop contact start to wear.


the signals for key switch is alright this is switched by applying 24V+.


the run stop how ever is switched to the minus and there for very sensitive for terminal resistance. 


last year visited a fleet of ships which had problems with this, the following dealers where involved and neither couldnt locate the problem.




South Africa



all it was is a relay of 5$.


good luck


Re: Caterpillar C9 Problem

Good day all,   I have a C9 in a generator that is having similar problems. The problem is intermittent but nonetheless is there, When I hooked up ET I had three codes 100-2 engine oil pressure erratic      110-2 engine coolant temperature sensor erratic     and a 590-9 engine control module abnormal


I replaced the OP sensor as in my SCADA system I recorded a spike well passed 100PSI in oil pressure,   I was testing the unit under load for about 3 hours when I had another spike past 100 and the engine just derated took about 10 seconds as the RPM fell off and then it tripped offline on under frequency. Can a oil pressure spike cause the engine to derate?   It seems strange that the oil pressure regulator would spike high and not low especially after it has been running for sometime. I do not want to condemn the HEUI pump but I am leaning toward that.   Any thoughts?


TY for the help

Regular Contributor

Re: Caterpillar C9 Problem

Hi Maskinmester,


Please provide us either with the serial number of your engine or contact your nearest dealer to get the needed support.

Best regards

New member

Re: Caterpillar C9 Problem

Hi, I`m engineer on bunker barge on Danish waters and I have similar problem with my C9D engine. One of my generators self stopped without any prior alarm. All parameters like press. / temp. during work are normal. We had already CAT serviceman on board to test engine without any results. To be sure that is engine problem we even disconnect genset from Power Management System to check did signal to stop engine do not come from PMS, but effect was same after a few hours (4-8) engine stop. On local display I only get info "Engine Stopped?"

Any advice will be welcome. Smiley Happy

Trusted Contributor

Re: Caterpillar C9 Problem

When you say CAT, I assume you mean the dealer?  If your already working with the local dealer, provide them with all the data and have their service department input a DSN (Dealer Solution Network) ticket to the CAT FACTORY to review and assist in the problem.  Each dealer should have a technical communicator who is responisble for documenting and filing technical reports/DSN tickets to CAT which then allows the factory technical engineers and experts to review all the data and comment accordingly.  


I assume you have checked for any service letters, PIPs, PSPs for your particular serial numbers?  Also, have the dealer look for updated ECM flashfiles, too.  


Id still pull a fuel sample just get as much data as possible to aid the dealer and factory to help eliminate factors.  CAT dealers should be taking this iniative if they are repeatedly doing Troubleshooting to no avail.  Make sure they involve the right people.




Nick C.

New member

Re: Caterpillar C9 Problem

I have put the ET on the machine myself to identify the problem. However, I never have the ET connected when the problem occurs. This problem is sometimes continous from startup or may not occur for weeks to months. I have run injector tests on the engine and checked all electonic solenoids and wiring from ECM harness up. i have followed the troubleshooting guide religiously. I have changed the speed sensor, and disconnected the TPS as so to rule out electro magnetic interference. I am waiting now to install a new set of injectors. If this does not fix the problem, I am going to install a new ECM. I have ruled out a fuel problem. My main engines, which are 3516's never have any problem with the fuel, as is the case with my primary C9 generator. I am burning clean ULSD, which is purifier up into the service tanks, then run through Racor filters before hitting primary fuel filters on the engines. The tug is 6 years old, and fuel tanks were clean last July during dry docking.


The worst part is that Caterpillar is aware of this problem, and do not know what is wrong, or how to fix it!!

Trusted Contributor

Re: Caterpillar C9 Problem

Have a CAT dealer connect ET to the engine while your under way and monitor the conditions to see if they can capture the event.  They can also run an injector test on it and see if that may be a cause.  You also could pull a fuel sample from the tanks and engine to see if any contamination and such.  



New member

Caterpillar C9 Problem

I am a chief engineer aboard a tugboat in Canada. I am having a problem with one of the generators, which is a C9D1 engine. The problem I am having is loss of RPM. When the engine is started, there is usually a cloud of dark smoke from the stack, which subsides after startup. The engine can be running without problem for hours, or even days before the problem begins. The engine will lose RPM momentarily, then regain the RPM. This rpm drop will eventually get worse, until the generator losses rpm completely and seems to go down to an idle. At this time there is alot of black smoke coming from the exhaust. The fuel pump is new. I am going to change the speed sensors and see what happens. I have also ordered some remanned injectors. The oil is becoming black after 100 hrs of running, which leads me to suspect that I have a fuel problem, or an electrical problem somewhere. Any advice would be great. We have been running with this problem for two years.