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intermittant RPM spikes at idle?

May 15, 2019, 06:57:59 pm

Last fall, after a 20 min drive while parked, in neutral idling the RPM's took off blowing black smoke 30 feet... I shut it down.  checked & tested several times before driving (w/o further incident) directly for service.  Service Center related it was a rub/short condition on two injectors that ran full open....  no damage, no fuel in oil, they "repaired the issue".    Jump ahead to yesterday... getting annual spring wellness check w/ filters and oil change....  while idling after service... it took off again!!! the mechanic, was right there and shut it down immediately. 


They found a lose connection at the Banks electronic unit, and a dried out harness with splices in it that they declined to work on, suggesting a chassis, Cummins, or Foretravel shop perform the work......

Thoughts? Suggestions? Similar issue w/outcome?

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Re: intermittant RPM spikes at idle?

Reply #1 – May 15, 2019, 07:51:16 pm

A quick search of Forum archives does not find a similar situation being reported.  You might have one of the very rare "unique" (to this Forum) malfunctions.  For the benefit of all members, do your best to report on what happened, and what the final solution is.

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Re: intermittant RPM spikes at idle?

Reply #2 – May 15, 2019, 08:47:54 pm

You might try PM'ing John Haygarth, the only forum member I know with a Banks system on a ISC Cummins. He had some wiring repaired at a Cummins shop in the Southwest. I think it had something to do with his Banks system...
Don

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Re: intermittant RPM spikes at idle?

Reply #3 – May 15, 2019, 08:56:58 pm

There's also the possibility of a turbocharger oil leak.

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Re: intermittant RPM spikes at idle?

Reply #4 – May 16, 2019, 12:38:26 am

Yes, Don is correct as we have the Banks system and would not want to be without it.
Now saying that my problem was not with the Banks other than the computer did fail on a few times but that was the 12v feed coming from the engine block to power the computer and it was a badly corroded wire that just needed replacing which I did.
This corrected it and has not since caused any issues.
We did experience  a race away engine  and it happened 3 times in over a weeks travelling and caused us nearly to have to drive off the road as I was not able to stop the vehicle when in rush hour I 10 traffic while going thru Phoenix.  It took the  Cummins shop a few tries to find the problem and that finally turned out to be an issue with the ECM connection to block. 3 of the brass pins were broken so the  normal 5 volt signal from the accelerator sender was giving false messages to ECM. It caused us scary moments to say the least.
Cummins Rocky Mtn in Avondale Phoenix found it after my suggestions that they remove the fuel filter next to it and take the ecm apart. It was the last place to look after they had replaced the sender and installed a new ECM and all seemed good till the next issue.
This is why I asked them to look  at original one to see if something was amiss. Once they saw the bad pins and fixed new ones there and returned my original one after reinstalling the engine info all has been fine since.
JohnH

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Re: intermittant RPM spikes at idle?

Reply #5 – May 16, 2019, 10:02:25 pm

Why would the connector pins break?

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Re: intermittant RPM spikes at idle?

Reply #6 – May 17, 2019, 10:58:56 am

Do not have an answer for that one but they sure we're damaged. I did not expect to see that as I was thinking just bad connections!
The Tech came for a long drive with me when he was doing a computer check of electrical system with it plugged into data port while I drove saw a bad voltage spiking and dropping in the output and input side of the accelerator sensor and as the max voltage is only 5 volts this did not take much to affect the engine running if it lost a few volts. Anyway the  long story (almost 4 days) of in and out service bays and testing finally convinced me that something was obviously wrong with the engine side of ECM.
We decided to leave the coach there as they were so busy and it was going to be a few days before they could get it back in that we drove in the car to friends in Mexico and stay in their CC and pick ours up on way back north. ROCKY Mtn Cummins felt bad about all this so they installed the new lift pump for free that Dave Metzger had sent me as there was now no rush to get it all done.
By the way they also allowed me to be in shop a few times during this diagnosis period which was good for me.
JohnH

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Re: intermittant RPM spikes at idle?

Reply #7 – May 17, 2019, 11:53:31 am

Quote from: Old phart phred – May 16, 2019, 10:02:25 pm

Why would the connector pins break?

You really don't want to see what people do to connectors.  Really.  It's ugly.

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Re: intermittant RPM spikes at idle?

Reply #8 – May 17, 2019, 07:26:39 pm

Force it!

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