Why the FCV is important!

Glend · **Posted:** Wed Mar 12, 2014 5:25 pm

Deleted by Author

geordi · **Posted:** Wed Mar 12, 2014 6:25 pm

Here we go again.

The computer has no way of detecting a runaway condition. The FCV is NOT designed to stop a runaway engine, or anyone that had their engine ingesting oil from a turbo failure. The engine should have (if it had the ability) detected the non-diesel-fuel source and the reduction in diesel needed for the given engine speed, and then activated this mythical runaway-prevention mode. This does not happen.

The FCV is commanded to close when the engine is shut down, so that the last injection event or two that will not properly combust (leaving unburned fuel as emissions) is attempted to be re-cycled back toward the intake rather than simply creating extra emissions and unburned fuel out the tailpipe.

Think about this: The FCV was added at the same time as the EGR device to diesel technology, on the behest of the EPA. Why would the EPA care about runaway Diesel engines? Simply put, they don't. They care about stopping emissions. Runaway prevention would be a safety design, and is not implemented.

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Hexus · **Posted:** Wed Mar 12, 2014 9:24 pm

Instead of re-posting all this, why doesn't someone just go necro-post the old ones every 120 days so we can re-read those?

geordi · **Posted:** Wed Mar 12, 2014 9:26 pm

Tell me about it.

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weeks101 · **Joined:** Mon Jul 30, 2012 3:29 pm **Posts:** 747

I decided to ask Keith at Green Diesel Engineering (GDE). This is what he has to say about the Flow Control Valve (FCV):

"There is no overrun protection with respect to the FCV in the software. The only overrun protection is zero fuel delivery above 4600 rpm…which does not help with a real overrun anyway in that oil is providing the combustion fuel in an overrun."

There you go, people. It's an emissions device. It does not protect against an overrun or a runaway.

thermorex · **Posted:** Wed Mar 12, 2014 10:07 pm

I wonder if a computer controlled injection diesel can in fact have runaway. In my opinion, when computer stops the fuel delivery, there is no fuel, other than the engine oil. I wonder how bad that engine can be to have so much oil delivered to have a runaway.

CATCRD · **Posted:** Wed Mar 12, 2014 11:41 pm

thermorex wrote:

I wonder if a computer controlled injection diesel can in fact have runaway. In my opinion, when computer stops the fuel delivery, there is no fuel, other than the engine oil. I wonder how bad that engine can be to have so much oil delivered to have a runaway.

Turbo oil leak is all I can think. Usually that goes out the exhaust on these engines though.

Glend · **Posted:** Wed Mar 12, 2014 11:52 pm

This pre-supposes that there is someone around with enough intelligence to turn the key off - thus shutdown.
If this annoys people get a moderator to delete it. I have helped enough people on this forum over the years, and have had enough of nazis who think they control what gets said.

I have asked the Moderators to delete all my past posts and threads from LOST

geordi · **Posted:** Thu Mar 13, 2014 2:05 am

Glen, please don't be like that. If you feel that I was trying in any way to censor your post, I apologize. That was not my intent. You have been very helpful here on a variety of topics, and that is appreciated by all.

On this single subject, the misinformation about the 'runaway-stopping' potential of the FCV somehow refuses to go quietly into the dark. There is a similar problem on the TDI club about the very similar "anti shudder device" that sits just before the EGR in the intake path. There are a great many there who believe that it somehow will magically stop a runaway, should the extremely unlikely ever happen.

The only purpose of my reply was to try and contain the misconceptions about the programming and function of that useless appendage on the intake. Somewhere, someone was told that it would "soften" the shutdown somehow and it was capable of stopping a runaway... And that tiny germ of false information has sprouted into a weed that refuses to die off no matter how many times it is pulled.

Billwill · **Posted:** Thu Mar 13, 2014 3:53 am

Glend, I fully agree with geordi here that you have greatly contributed to this forum and there is no way that you must leave here and have your posts deleted.

Besides, how else am I going to get all the useful information about Export CRDs that you have been providing all this time. :wink:

Rich · **Posted:** Thu Mar 13, 2014 10:39 am

air in the fuel?

:ALONE:

papaindigo · **Posted:** Thu Mar 13, 2014 10:57 am

X3 on please stay Glend.

I've paid a bit of attention to a variety of diesel engine run away posts and about all I can say for sure is:
1. a true run away occurs when a source of fuel in excess of normal fueling is induced into the intake.
2. I do not recall any member having a run away caused directly by the most likely source on a CRD which is a massive oil leak from the turbo into the CAC hoses and hence into the intake.
3. I do recall one member who suffered a, fortunately, brief run away that was, IIRC, indirectly related to a turbo oil leak. My memory of that case is the turbo was replaced but the intercooler was not cleaned and upon restart and attempted ignition shutdown the residual oil in the intercooler caused that brief run away.

For what it's worth to the best of my knowledge stopping a run away:
1. cannot be done by switching off the ignition - all that does is turn off normal fuel delivery.
2. stopping a run away requires cutting off the external cause of non-normal combustion which typically would mean stopping the flow of air to the intake. There are after market products that can be installed to do this.
3. almost forgot mainly because it doesn't apply to "domestic" KJ CRDs that only come with automatic transmissions but in theory it is possible to stop a run away on a diesel with a manual transmission if you deliberately stall the vehicle

thermorex · **Posted:** Thu Mar 13, 2014 12:43 pm

CATCRD wrote:

thermorex wrote:

I wonder if a computer controlled injection diesel can in fact have runaway. In my opinion, when computer stops the fuel delivery, there is no fuel, other than the engine oil. I wonder how bad that engine can be to have so much oil delivered to have a runaway.

Turbo oil leak is all I can think. Usually that goes out the exhaust on these engines though.

Correct, I omitted that. Bottom line is that you really have to be way due on maintenance and inspection of your engine's health to have a runaway. Checking for turbo play should help prevent it.

Papaindigo is correct with runaways, intercooled engines don't get it so easy due to the intercooler trapping some of the oil. I can see it happening though.

Glend, come on man! Some of us may have Nazi temptations, but that doesn't mean we don't appreciate your input. I'd say that even if some threads are bothersome for some people, they are still useful for the regular reader since it refreshes some info.

Rich, it's only your fault with your air in fuel, lol. Now I have one more thing to worry about

.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

I have never had a diesel runaway, but wouldn't it be feasible to put the CRD in drive with full brakes and let the tranny hold it down to a reasonable rpm? If the engine kept on running for longer than 20-30 seconds, it might start overheating the tranny. In most cases the engine should stall out in a shorter period of time. Of course, you would have to react fast to save the engine in the event of a run away.

A lot of things have to go wrong for a run away CRD. Most folks on the forum have the opposite issue, the CRD doesn't want to run at all

tjkj2002 · **Posted:** Thu Mar 13, 2014 1:31 pm

GreenDieselEngineering wrote:

I have never had a diesel runaway, but wouldn't it be feasible to put the CRD in drive with full brakes and let the tranny hold it down to a reasonable rpm? If the engine kept on running for longer than 20-30 seconds, it might start overheating the tranny. In most cases the engine should stall out in a shorter period of time. Of course, you would have to react fast to save the engine in the event of a run away.

A lot of things have to go wrong for a run away CRD. Most folks on the forum have the opposite issue, the CRD doesn't want to run at all

Try stopping a 8V92TA at full bore.Fuel racks closed,all 7 fuel lines cut,1/2" steel plate covering turbo inlet,on fire(from no valve covers),and then finally about 25 gallons of water through the turbo inlet before the block broke in 3 pieces.Fun times when someone thinks messing with the buffer switch was a funny prank till he got sacked with a $35k bill for a new engine.

flash7210 · **Posted:** Thu Mar 13, 2014 1:39 pm

tjkj2002 wrote:

GreenDieselEngineering wrote:

I have never had a diesel runaway, but wouldn't it be feasible to put the CRD in drive with full brakes and let the tranny hold it down to a reasonable rpm? If the engine kept on running for longer than 20-30 seconds, it might start overheating the tranny. In most cases the engine should stall out in a shorter period of time. Of course, you would have to react fast to save the engine in the event of a run away.

A lot of things have to go wrong for a run away CRD. Most folks on the forum have the opposite issue, the CRD doesn't want to run at all

Try stopping a 8V92TA at full bore.Fuel racks closed,all 7 fuel lines cut,1/2" steel plate covering turbo inlet,on fire(from no valve covers),and then finally about 25 gallons of water through the turbo inlet before the block broke in 3 pieces.Fun times when someone thinks messing with the buffer switch was a funny prank till he got sacked with a $35k bill for a new engine.

Oh yeah!
Those old Detriot 2-strokes were fun, weren't they?

Ever gotten one to crank over in reverse?
Blowin exhaust out the intake. Fun times.

tjkj2002 · **Posted:** Thu Mar 13, 2014 2:38 pm

flash7210 wrote:

Oh yeah!
Those old Detriot 2-strokes were fun, weren't they?

Ever gotten one to crank over in reverse?
Blowin exhaust out the intake. Fun times.

Yep sure had one that did that.It would start normally but once you put it into gear the crank would slow down,stop,and start running in reverse.The Alison trans was messed up causing it.

Tinman · **Joined:** Mon Apr 10, 2006 10:45 am **Posts:** 308

How much oil would it take to cause run away? In stock configuration the CCV pumps a ton of oil in the intake. I changed glow plugs a few months ago and noticed the intake covered in oil all the way to the fcv. Not pooling up on anything but like other crd's I've seen with stock ccv. It's coming from the turbo so I have another one sitting on the work bench. All this runaway talk has go me worried now. Should l drive it? BTW why won't the fcv stop a runaway if one turns off the engine?

geordi · **Posted:** Sun Mar 23, 2014 11:10 pm

The CCV flow is completely normal. The amounts of oil to cause a runaway are immense, and much more likely to be supplied in concert with a turbo failure... That is an exceedingly unlikely scenario for two reasons. One, if the turbo fails, you would be shutting off the engine before a runaway because of the power loss and massive smoke screen behind you.

The second main reason is that the oil would have to be brought in large amounts all the way through the intercooler and intake, before you shut the engine down, and that is a massive amount of volume to pass through.

Why the FCV is important!

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