Engine keeps running

wolfe10 wrote:

Terryallan wrote:

wolfe10 wrote:


Inline shut-off valve-- never seen one on that chassis, but a VERY good idea on the inlet side of the primary fuel filter.


.

Our Cat had one. And yes we had to use it.

They are a great idea.

What chassis and coach? Very rare to be installed by the chassis maker.

Without it, when changing fuel filter you either have a mess from a diesel leak, or get a lot of air in the fuel line (depends on whether level of fuel in the tank is higher or lower than the filter head.

Was a Ford. CLT9000. Not a RV. But I figured it was standard on Cats. Guess I was wrong. Just another "better idea" from Ford.

Ya, I suspect a mechanical pump not electric. But killing 12 VDC to the ignition/engine should shut off the engine. Yes, the exception would be a run-away engine (EXTREMELY rate-- in fact in 18 years I have been on the forum, have never heard of it on a Caterpillar engine).

Probably time to let the OP get back to us to narrow down the speculation.

klparker wrote:
Have 2001 Itasca, 220 caterpillar diesel. When I turn the ignition off, the engine keeps running. Any idea why this is happening.

Thanks

I'm going to assume this is a typo. Never heard of a "220" CAT, especially in this era coach. Most likely a 330HP 3126 CAT.

"Posted By: Terryallan on 07/11/18 02:42pm

Usually there is an inline valve to shut off the fuel supply"

Nope, no inline fuel valves anywhere on all the CATs I've seen and or worked on in this era coaches. I installed TWO. One before the rear fuel filter and one after it. Now, no possible chance of air entering the system and or, fuel draining back into the tank, as it did prior to my installation of the fuel shut off valves.
Scott

Posted By: jdealcpa on 07/11/18 08:23pm

My 2006 Cat 350 does this every so often. I have changed the ignition switch, been over every thing I can think of, as has the local Cat shop. I merely turn the engine batteries off. My fuel pump is electric so that kills the engine. Problem hasn’t cropped up for a while. So I don’t know if it’s fixed or ???? Good luck.

Your fuel pump is ELECTRIC? May I ask what year/make/model/chassis coach you have that has an electric fuel pump in a CAT equipped coach?

The reason I ask is, our coach, an '04 Itasca Horizon 36GD with the CAT C-7 330HP only has a lift pump that is attached to the back of the HEUI pump. Of course, neither of those are electric. Just wondering.
Scott

johnhicks wrote:
For my old 6BT5.9 I have a fuse labeled IGN that'll shut it right down if pulled.

If you lose a turbo oil seal and it's running away, killing the ign. wont have any effect.
You have to plug the air intake to choke it off.

Yes, while hard to diagnose over the internet, an electrical issue is by far the most likely cause. Things like stuck contacts in the ignition solenoid, bad ignition switch, back fed 12 VDC to the ignition circuit, etc.

That is why "what else is working as it should/not working as it should is a good place to start. For example if other things that should only work with the ignition on do not turn off (Allison shift pad, dash HVAC fan, etc) you have pretty well narrowed down the problem.

But we do need to OP to get back to us with this information!

I had somewhat of a similar issue whereas if I had my generator running, I could not shut down my Cat 3176b....a back feed of some sort. Funny thing is, I had a battery explode and once I replaced said battery, the problem disappeared. Weird?????

BigSkyBob wrote:
You are gonna think this is utterly stupid but it happened to me twice. When my toad electrical cable was attached to the toad I was getting a "feedback" somehow that allowed my CUMMINS engine to continue to run. When I unplugged the cable to the toad it stopped running. Luckily I was at the factory for other work and one of the techs figured this out. Just food for thought.

Weird!

One way I can think this would happen is if whoever wired up the towed wiring did things wrong in two ways, 1) Connected the power wire from the umbilical directly to the battery without using a blocking diode; 2) AND in the RV, wired the power source for the towed to an IGN wire instead of directly to a battery.

Doing those two things wrong would allow the fuel pump to be back fed from the towed's battery and it would keep pumping fuel and the engine would keep running until the umbilical was unplugged.

At least that's what I think may have happened to cause it.

You are gonna think this is utterly stupid but it happened to me twice. When my toad electrical cable was attached to the toad I was getting a "feedback" somehow that allowed my CUMMINS engine to continue to run. When I unplugged the cable to the toad it stopped running. Luckily I was at the factory for other work and one of the techs figured this out. Just food for thought.

ScottG wrote:
Yea Brett, a turbo diesel can lose a turbo seal and "run away". If it's a big enough leak, it will run well beyond max RPM since the gov. is out of the circuit. Either way, unless you plug the intake, it will run until out of "fuel" and seize.
There are countless videos on Youtube of this happening. Pretty entertaining!

Scott,

You are absolutely correct-- a more common issue on the Detroit 2 strokes, but lubricating oil is/can be a "fuel" if a significant leak of the turbo oil seal on the intake side of the turbo. If the leak is massive enough, as you said, it can allow the engine to "run-away".

But the OP did not mention run-away RPM and/or seized engine. Just, "I can't shut it off". Would prefer to direct them to the more common causes, not scare them with the "worst case scenario".

Terryallan wrote:

wolfe10 wrote:


Inline shut-off valve-- never seen one on that chassis, but a VERY good idea on the inlet side of the primary fuel filter.


.

Our Cat had one. And yes we had to use it.

They are a great idea.

What chassis and coach? Very rare to be installed by the chassis maker.

Without it, when changing fuel filter you either have a mess from a diesel leak, or get a lot of air in the fuel line (depends on whether level of fuel in the tank is higher or lower than the filter head.