Multifuel exhaust

[cranetruck]

What is the process here, the visible exhaust is a lot worse from the multifuel when the engine is not driven a lot.
Currently, my deuce even idles without any visible exhaust (it has been driven long and hard), while the 757 smokes like the dickens. It has not yet been on the road and seems to suffer from past years of long idling periods. I'm curious to see how much driving it will take to clear the exhaust, but what is the reason for so much smoke after long periods a low rpm and power?

Under what conditions are the EPA judging an engine exhaust, at idle or at load?

 

[beaubeau]

There are many reasons why a Diesel will smoke alot.. Black smpke may be from idling too much,Old diesel, be sure to check UR air cleaner and air passages{Mouse nest}, and even pulling the Trottle and let it run in place for10 minutes at about 1200,to1500 rpms. Watch UR gauges, oil, temp, even Voltmeter. Try using Diesel conditioner, or even Type F trans. oil helps clean out fuel system. Remember a Diesel is made to run Hard!!Running agains the Govenor under a load is good! It wants to Work!! Good Luck, Phil

 

[ygmir]

might also be fuel and byproduct crud built up in the exhaust system from not getting hot and burning it out.......

 

[Recovry4x4]

As Henry pointed out about crud buildup, last year I replaced the J pipe on the 275 right before the GA Rally. It was a used item and had some serious crud in it. I drove it around town for a week and still never burned the stuff off. Wasn't till the 750 mile ride the crap finally went away and stopped smoking.

 

[jimk]

You might have to run it hard [once] to know if smoking at idle is normal or from its lack of use. Maybe poor quailiy fuel(old) is making it smoke? A hard driver probably has fresh stuff. i would guess running hundreds of gallons thru might keep injectors clean. Idlers may not get up to operating temps. Engines run hard have hot parts -hot pistons, ex valves, intake manifold, injectors and even the fuel and air (after passing over parts) may smoke less because combustion is more complete. Just increasing the rpm a tad can do that too. A few years ago the NJ DOT was spot checking commercial vehicles incuding an exhaust emission test for smoke/particulate matter (at idle). Our new Macks were failing because while the test allowed a fast idle(1000rpm instead of 600?) Drivers were unaware and letting truck idle slow. Slight increase in idle speed would pass test. Maybe smoke is blowby (oil)?. Maybe look see at nozzle spray, a compression/fuell press tests? Turbo seals are crude and may pass oil at idle. Running hard the exhust gas pressure may slow leakage and high egt may burn what gets by.

 

[cranetruck]

Thanks for your insights!
They kind of agree with my own experiences. There is one (big?) factor with the 757 engine that may play a role here and that's the feeding of the blowby into the exhaust. This is done to make it possible to run the engine under water without preps.
I plan to make some changes to this detail and it will be interesting to see the results....

 

[ygmir]

wow,
interesting feeding the blowby into the exhaust......
How fun to put a WMO pressurized feed and make a smoke screen.........hahahahaha

like the Batmobile..........

 

[m-35tom]

bjorn, i have never tested injectors and had more than 3 good. the engine will still run sort of ok but the jet of fuel rather than a fine mist will cause more smoke. since i put all new injectors and new ip head on, almost NO smoke at idle when hot and little even when cold

 

[imported_Squirt-Truck]

Cranetruck, you are also comparing an LDS to an LDT engine. Have you looked at the injetors? I believe that the -1 engine used 2 hole injectors like many of the LDT's but smoke and such from the higher fueling rate drove the development to the -1A engine, which has single hole stream injectors. If you put atomizing injectors into one of these it will smoke severely and not be tolerant of differing fuels. I suspect that your -2 engine is simply a higher fuel and boost rate than the -1A. Every -1 and -1A engine I have been around smoke badly at idle, except when running at full temperature of 200F, even then they smoke some. Just off idle the smoke clears untill a load hits. Earlier this week Squirt was over the road at just over 54,000# and yes she smoked on the hills at full temperature and throttle, but at 47 MPH she was clean, just a heat trail.

Get her ready to run hard and then see how (if) she smokes.

 

[kipman]

My deuce, rebuilt with 212 hours and C turbo does not smoke at idle, when you blip the go peddle it smokes as it should. This is on new diesel.

 

[roger-wilco-66]

During my restoration of the deuce I needed it to run in high idle (900-1000 rpm) for airpressure over a prolonged time. I noticed that it didn't like that particularly. It dribbled oil out of the breather tube and leaked a little through the exhaust manifold gasket (presumably unburned diesel). Also, it started to smoke considerably more.
When I got her on the road again I went pedal to the metal on the autobahn. After that: no more smoking, no more dribbling or leaking. Also no smoking when idling anymore, just the normal "belch" when hitting the gas pedal. I guess the goo got burned away during the ride.
Feeding the oil-breather into the exhaust system doesn't really mitigate that problem did you check what happens when you plug that thing?

I like your project, fascinating truck.

 

[cranetruck]

.......
Feeding the oil-breather into the exhaust system doesn't really mitigate that problem did you check what happens when you plug that thing?

I like your project, fascinating truck.

Yeah, feeding the exhaust oil and fumes from the crankcase can't be good, okay for swimming, but that only applies to the M656 cargo version anyway. Haven't gotten around to work on that particular detail. On the deuce, I filter it and feed it back into the air intake....

These vehicles were more common in Germany than aywhere else, some 400 should still be in Europe, while a max of about 100 were ever in the US. The hull of this amphibian is aluminum, so scrap value is high.

 

[m-35tom]

my vote is still for dirty injectors, they will cause all the symtoms described. i can run mine for 20 minutes at 1000 and nothing....... bjorn, lets find that 656 and import it.

 

[WillWagner]

Been watchin'. I think you should wait 'till you get it out on the road to clean it out. Who knows how many hours it was operated at idle or no load before you got it. I is most likely just full of years of crap.
Will

 

[cranetruck]

my vote is still for dirty injectors, they will cause all the symtoms described. i can run mine for 20 minutes at 1000 and nothing....... bjorn, lets find that 656 and import it.

Dirty everything, from long periods of idle. The people I have communicated with (email) that were trained on these at Ft Sill state that the trucks were mostly just started and sat at idle and not driven hard also born out by the odo and hour mtr, which I have no reason to doubt.

My original question was about the process and from your responses, I must conclude that build-up of unburnt fuel, "crud", inside the combustion chamber (including on the injectors), which burns off, is the cause here. Perhaps some buildup in the exhaust system also. I have installed two EGT thermocouples, so that I can detect a difference between the front 3 injectors vs the rear 3.

...still like to know the condition and version of the engine(s) EPA tested and what the results were. The hypercycle is supposedly a more efficient combustion process. To quote BobS, "When White attempted to modify the multifuel to meet emissions, the engine failed miserably". Why did only one manufacturer work on this?

Tom, one reason for my posts is to generate some interest in these vehicles and perhaps we can save another, not just for the engine (hate to see it removed and not used as intended), which was designed for this series of trucks exclusively. The injection pump and FDC are also different to work with the automatic (reduces rpm during shifting or something to that effect).

 

[Pinkie]

Can some one post pics or video of what they think is exceptable amount of smoke? Does anyone have anything on youtube about it?

 

[steelandcanvas]

I thought I'd chime in on this thread, the diferences are interesting. My LD-1 smokes when I first start Her up, after about 5 minutes of a 1K RPM idle, clear as a bell. Now get in a drive Her hard, She'll smoke all the way through the gears, then clear up when cruising. Normal? I use Disel-Kleen additive and the fuel is fresh. I run Her about 5 miles or so every week, and longer when I have the coin to put fuel in Her. Suggestions welcomed.

 

[scooter01922]

I think i'm in the same boat as you steelandcanvas. A bit smokey at startup but after a few min of warmup time, all clear. Puts out a nice puff of smoke if you give it some go pettal though. But that i like

 

[steelandcanvas]

Puts out a nice puff of smoke if you give it some go pedal though. But that i like

 

[BKubu]

Bjorn, I saw a test video comparing several of the vehicles we own in various off-road settings. I was thoroughly impressed with the M656/M757 trucks. They did almost as well as tracked vehicles in mud, even out-performing them in certain situations (the 60 degree slope and the tank trap come to mind). The GOER was also a beast. The M35 did not do that well...at least to me. It seemed to get bogged down in every situation.