ISL400 wouldn't stop running - where is the fuel shutdown solenoid?

[Rambling Roos]

Hello, Monacoers!

We have a 2007 Beaver Contessa 42’, that we purchased 3 years ago. This one is equipped with a Cummins ISL 400. I’m looking for help in locating the fuel shutdown solenoid.

This part is only incidental: I recently found that the alternator wasn’t pushing enough voltage to maintain the chassis battery. In the process of resolving that, I also did some cleaning in the engine compartment (bad oil leak that I also have yet to track down).  The cleaning may be the cause of my current problem.

After the repair, we started up the engine and confirmed that the alternator is fixed, but then found that we could not shut down the engine. The ignition was clearly off (and all auxiliary power was off, so pretty sure the ignition switch is working correctly). That led me to search for the fuel shutdown solenoid, or the fuse to it… but I came up empty-handed. Eventually, I pulled the fuse for the ECM which finally killed the engine, of course. However, I now have the question: Where the heck is the shutdown solenoid? I’ve looked on Cummins QuickServe and this engine appears to have the fuel rail system, but in none of the diagrams do I see the shutdown. Nor do I find any fuse (in the rear bay or in diagrams) that is labeled for the fuel shutdown.

I must be missing something, because my understanding is that there really HAS to be a fuel shutdown somewhere. I’ve looked on and around the fuel rail and other than the feeds to the injectors, the only thing I find appears to be the pressure sensor.

EDIT:  On the Beaver FB group, someone told me that ECM controlled engines don't use a fuel shut down valve, so that would explain why I can't find it.  Now the question is what else could be keeping the engine running with the ignition off?

Can anyone offer guidance on locating the fuel shutdown? Or any other ideas on the cause of the engine failure to shutdown?

I appreciate your help!

--Roger
  2007 Beaver Contessa Bayshore 42’
  Cummins ISL 400, Allison 6-speed

 

Edited June 7, 2023 by Rambling Roos

[Frank Bergamo]

Did you replace alternator or rebuild the original? When replacing alternator you need to make sure it is the same as the original or you can get back feed from the ignition circuit. A diode in the ignition circuit will remedy your no shut down situation if this is what is going on. Hope this helps.

[TomV48]

I have a 200 amp continuous duty cycle solenoid set up to activate from ignition power switched from the ignition relay delay.  IRD.  At one point while using that ird current source to activate my DC to DC Renogy controller I was back feeding 12VDC TO THAT IGNITION SOURCE LINE FROM THE IRD.  Outcome was the ignition switch no longer stut off the engine.  I quickly disconnected my back feeding lead and found a different way to wire it.      The moral, look for something else you did that is back feeding power to the ignition that is not allowing the engine to run on.

[waterskier_1]

You either have an incorrect alternator as Frank posted, or the replacement alternator is incorrectly wired allowing 12-volts to be continuously fed-back to the ignition relay effectively eliminating the ignition switch once started. 

  - Rick N.

Colorado Springs, CO 

[Frank Bergamo]

Roger,

you can easily check to see if it is back feeding by disconnecting the ignition circuit from the back of alternator while coach is running. If it shuts off once disconnected, then it is back feeding. By placing a diode in the ignition circuit at the back of the alternator, it will remedy your problem. Hope this helps.

[Rambling Roos]

Thanks for all the good suggestions.  In fact, I tried basically the test that Frank proposed (disconnected before starting because I can't safely get to the back of the alternator while the engine is running).  Lo and behold, that was the problem.  So now, I need to figure out why there is current feeding back into the ignition circuit.  I can't see how that would be, unless there is something simply wired wrong inside the alternator.  I'll consider the diode if I don't find some other cause.

The curious thing is that I expected the alternator to not generate anything since it didn't have the ignition trigger, but I was getting 14+ Volts out of it (amperage is a different question - no convenient way to measure that).  

In any event, I have a workaround for now, and a long-term fix (diode) if necessary.

Thank for the help, folks!
--Roger

[Ivylog]

Fuel solenoid fuse is on the rear start board… right hand one of the 2. Left one is for the starter circuit. 

[TomV48]

21 hours ago, TomV48 said:

I have a 200 amp continuous duty cycle solenoid set up to activate from ignition power switched from the ignition relay delay.  IRD.  At one point while using that ird current source to activate my DC to DC Renogy controller I was back feeding 12VDC TO THAT IGNITION SOURCE LINE FROM THE IRD.  Outcome was the ignition switch no longer stut off the engine.  I quickly disconnected my back feeding lead and found a different way to wire it.      The moral, look for something else you did that is back feeding power to the ignition that is not allowing the engine to run on.

I was probably not entirely clear. To the solenoid I'm talking about is the solenoid that allows the truck charging circuit or the truck batteries to jumper across and charge the house batteries.   Not only did I inadvertently feedback 12 to the ignition trigger side of that coil, I can envision several ways and internal failure in that solenoid or other ignition charged points that could feed house or truck battery current over to the ignition and since they share a common ground the difference would be the same. Your ignition switch would no longer shut the engine down.  So if there's nothing else that you changed recently then I would explore possible feedback loop through any 12 volt source that is on an ignition controlled circuit

Edited June 8, 2023 by TomV48

[waterskier_1]

2 hours ago, Rambling Roos said:

Thanks for all the good suggestions.  In fact, I tried basically the test that Frank proposed (disconnected before starting because I can't safely get to the back of the alternator while the engine is running).  Lo and behold, that was the problem.  So now, I need to figure out why there is current feeding back into the ignition circuit.  I can't see how that would be, unless there is something simply wired wrong inside the alternator.  I'll consider the diode if I don't find some other cause.

The curious thing is that I expected the alternator to not generate anything since it didn't have the ignition trigger, but I was getting 14+ Volts out of it (amperage is a different question - no convenient way to measure that).  

In any event, I have a workaround for now, and a long-term fix (diode) if necessary.

Thank for the help, folks!
--Roger

I'm not sure what you mean by "Ignition Trigger".  Did you have your alternator rebuilt, or did you buy a new alternator.  I suspect if the later, you did not get the correct alternator.  It must be a DUVAC alternator.  If you did rebuild or get the correct DUVAC alternator, then it is not wired correctly (or, possibly, a defective rebuild or alternator, but unlikely).  I have worked with many people who have this problem, and it is always either the incorrect alternator, or incorrect wiring.  I am not a proponent of addidn't additional diodes or switches to "force the square peg in the round hole".

  -Rick N.

[Frank Bergamo]

When I replaced a Duvac Leece-Neville alternator with a Delco Remy I got the back feed that would not shut down the motor when turning off ignition. By trial and error I figured out what needed to be done to get engine to shut off. Don’t know if original Leece-Neville had an internal diode that prevented back feed, but by placing diode in ignition circuit on the Delco-Remy, solved the problem. So, at that point I could have removed the Delco-Remy and replaced with a Duvac alternator or just run what I had.  I chose to leave it and never had a problem with the install. The guy I sold it to is still running it today with absolutely no problems. If it were me, I would put a diode in it and forget about it. Hope this helps.

[Rambling Roos]

Frank, you are right on target.  That is exactly my scenario.  The thing is, I replaced the LN Duvac with a Delco 28si, which also says it is Duvac and it has the ignition excitation function like the LN.  It still doesn't seem like it should be feeding anything back over the ignition line, but I'm convinced that is what is going on, and with your experience, I'm also convinced that the right solution is the diode.  I've already got some in my Amazon cart 😁.

Again, thanks for your insight.