6V92 fuel dilution.

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Sorry it's not a UOA to ponder....I know the UOA forum for HDEO has been slim as of late...
I know it's not the correct forum necessarily as the application are not in a truck or commercial vehicle, but we have three units where I work (6V92's) which are used as fire booster pumps. Idea is they kick in when the water level drops below a preset level, and assist with the regular process.
I've been going over the reports that have come back lately (I've only been at this current place a year and a half), and I have noticed they have been coming back with 5-7% fuel dilution for a number of years. I had a theory that the conditions in which they ran were suspect, but now I'm thinking the inherent design of the fuel injection system (unit injectors?) may be the culprit. I recall 6V53's having unit injectors, not 100% if the 92's do. Ours are activated electrically from a remote source which engages an electrically operated switch on top of the governor, and then finally engages the fuel rack...may happen quick, but that's a lot of stuff in between...
Pumps are always started an run at 1900 rpm, in which they get there within a second, like most 2 stroke detroits. Then, they're always shut down at the same rpm, no cool down, nothing. 1900 and then off...
So if it was just one unit, I would be looking for issues mechanically, but it's all 3 which have the fuel dilution. And it all shows up around the 20 hour mark. Always run at 1900 for about 1/2 hour per week, but sometimes they start and run if the water drops.
Ideas?

Oil is always straight CF/CF-2 40 weight, if the question arises.
 
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do they always run a 1/2 hour? are they ever run for only a few minuts? if they are cycled a lot with out getting hot, that might explain it.
 
Good point, I thought about that too, but they are strictly run 1/2 hour per week due to fluctuations in water levels...We're typically not allowed to run them for short times as this can cause abnormal readings for water plant, fire dept etc...and it's always coordinated when we do run them.
It's just the 1/2 hour per week, and then they run when sensing registers a drop in the lines.
 
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No Doug, mechanical...two stroke, I think they were built in 1984 or so...apologize for the inadequate description. Not sure when some of the electronically controlled DD engines started coming in...1987? a little later. No matter, these are definitely mechanically injected.
Our controls electrically operate the engine. It's a stationary engine in a heated room. We have have a control panel similar to a transfer switch to remotely operated the engine.
 
1/2 hr is not long enough to get everything up to operating temp in that engine. 1900 rpm is a little low for them too. Those need to stay @ 2100-2200 and as little idling as possible.
 
They don't call the 6V & 8V Dripdtriots for nothing. After rebuilding a few of those, I say injectors injectors injectors injectors and agree with the above statements. If it's a 92, I'm guessing it has four tappet valves per cylinder. Is this a blower, turbo or both? Your problem you are encountering is why a straight weight is used on these "V type 2 strokers. Despite the fact they leak, drip and burn oil, I have seen some of these engines read high on the dipstick after 100 hours of use on heavy equipment even with newer injectors. Are you using a straight 40wt?
 
Yep, straight 40...always straight 40 in the DD 2 strokes...we used to run 15W40 on the 6V53's we had in the Army, and they never really lasted.
Hey Michael_P, I'm quite certain these models have the unit injectors, am I right? Could the linkage and related components to those have anything to do with it? Do you think it's an injector issues inherently, or a mechanical issue due to wear/run time? Has the usual roots blower, and a turbo. I checked today and they were assembled in 99...but they are mechanical for sure. We have a solenoid actuating the fuel rack on top of the governor housing.
We have them plugged in using a circulating block heater in an already warm room, but I guess 1/2 hour under those conditions still isn't enough...
 
They are only Detroit diesel 6v92s what ever designation . I went out on a Coast Guard boat and the boat had 2 electric (DDEC} 6v92 and the data plates listed the HP over 400!
 
Yeah, these are 385 at rated rpm 2350 IIRC. These don't have an ecm of any sort on the engine. Our control panel was wired in after to control the engine. I'm guessing they would still have the unit injectors as found on the 6V53's.
 
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Yeah, the unit injectors sit squarely in the middle if the tappet valves. I doubt the linkage would have anything to do with it, but I will consult a DD expert. I did search the net and found some interesting sites by googling 6V92. They have been known to leak fuel from the electrical area too IIRC.
 
I had a very similar issue with our fire suppression system back-up pumps when I worked at Ford. We ran a 2hp electric "jockey pump", then a 100 HP electrip pump, then three DD's of various size/vintage brought on consequtively. When everything was running at full tilt, the system could move a LOT of water. We had two 500,000 gallon tanks outside for reserve.

We used to run them every week for about 15 minutes, just to cycle them, with no load. Then we started doing UOAs. Shocking to say the least; they leak fuel badly; must be inherent. Didn't seem to hurt them, but certainly isn't desirable.

We ended up running them weekly for 1 hour durations, and loading them up by cycling the tank water back into the tanks via loops we installed. Seems that those engines simply were not made to be run "lightly"; they need to "work and work hard" to run right.
 
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Thanks for your comments, Dave. Yeah, DD's certainly have that distinction of being an entirely all or nothing engine.
Thanks for looking into it futher, Michael_P.
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Originally Posted By: Chris142
When those engines are used in a truck the proper way to drive them is mad. Slamming your hand in the door is a effective way to get mad enough to drive them.


That's what my Dad tells me when I drive his 671. "You've got to drive it like you hate it!" is his mantra.
 
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Originally Posted By: Chris142
When those engines are used in a truck the proper way to drive them is mad. Slamming your hand in the door is a effective way to get mad enough to drive them.


Sounds like you're a man of experience...how's the hand?
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Years ago I used to drive truck out of the Teamsters line driver union hall to make extra $$$ when I was young ,tireless and ambitious and got to drive many different engines . The non turboed 2 cycle Detroits needed to be run at max governed RPM to make power .The turboed engines in the 8v71 series did pretty good but when the 92 series came out they had tons of power and a feul squeezer 8v92 would out pull a 350 cummins big cam . The 350 HP Cummins was a pig in comparison. The 6v92 turbo engines at the higher rating which was way lower than the marinized . would be equal to almost equal with a 350 Cummins. I at the time wouldn't want a Detroit 2 stroke if I had to buy one even though I liked how the 92 series ran . From my fading memory the feul squeezers ran at max governed rpm at 1950 RPM and the high output was at 2100 or 2300RPM
 
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