starting an 8v71

[challenger440]

So what is the best way to start my 8v71?  Dash plaque says not to depress the clutch while starting, but in cold weather trying to turn over a cold 4 speed with 90w seems like a quick way to wear down the batteries. 
  During normal weather and a cold engine how long should I crank on it.  10 or 15 seconds and wait one minute, try again?  Clutch out?  Should I ad in a little throttle like an old carbureted engine?

Are there any "secrets" to starting?

Thanks, John M.

[Len Silva]

Are you sure the tranny has the right oil?  The 4 speed Spicers in GM buses used 30 or 40 weight engine oil.

[bevans6]

You can depress the clutch if you want to but the downside is you will harm the thrust bearings on the crankshaft.  The thrust bearings are not properly lubricated unless the engine is running, they depend on hydrostatic pressure to work.   You can get synthetic oil, MCI's used SAE 50, if you want.  The things that can help start a mechanical 8V71 are a block heater and turning the engine over with the rack in no-fuel for a few rotations so that the combustion chamber warms up.  You can do that with the engine stop lever on top of the governor.

Brian

[challenger440]

Well cool.  Learned something new.  PO mentioned they stood on the clutch for cold weather starting.  the tranny does indeed use SAE 30 according to the manual. Diff use 90 or 140 depending on temp.  Brian your saying clutch in pushes the pressure plate flywheel enough to take out the thrust bearings.  Thanks for the info, glad I looked at the dash plaque.  j

[bevans6]

diff isn't turning when you are starting, all that is turning inside the gearbox is the gear clusters.  On the thrust bearing, what I'm saying is that the way it gets lubricated is such that it's oil film is very degraded in it's ability to protect until the crank is spinning.  the spinning motion of the crank relative to the stationary bearing is what helps build a pressure in there that lets the bearing survive.  It's designed to start with the gearbox in neutral, so that's what you should do particularly on a cold start.  Not to say it will kill the thrust bearings in 10 seconds or anything, just that it's not particularly good for them.

Brian

[artvonne]

  I started a Mercedes 300 diesel at zero F once without plugging it in overnight, I let it cold soak. I did it on purpose just to see if it could do it. You hear so many claim their diesel would start down to -10F, -20F, I never believed it and I still dont. Zero is really cold, and if the engine has sat in it for any time, the combustion chambers are just as cold. The fuel is just as cold. At zero degrees, your attempting to compress dry, zero degree air high enough to surpass the auto ignition temperture of zero degree fuel oil. And those zero degree combustion chambers suck that heat away really fast.

 I turned on the glows and it seemed to take forever to turn out the light. You know, at zero your lucky to have half a battery, and now your sucking it down running high current glow plugs, longer than they ever glowed before, and whats left of that now tiny battery still has to flip the engine over fast enough for the laws of physics to take place.

 I hit the starter and immediately told myself it wasnt gonna work. It was cranking, rather slow I might add, and quite surprisingly white smoke started falling out the tail pipe. I do mean falling, it looked like cold smoke. Then it kinda fired a bit, then went back to just cranking. I turned off the key, turned it back on, and proceeded to make the now small battery even smaller. The light went out, I started cranking, and dang if the bugger didnt start knocking and thumping. Little by little it gathered speed until it actually started to run on its own. But running wasnt the right word for what it was doing exactly.


 It sounded horrible. It was running, but white smoke poured out the back, and that poor little engine knocked and thumped and shook so bad I thought it was going to crawl out of the car. The whole car was shaking. I knew enough to know it had a dead cyclinder or two that didnt light off, so I shut it off and relit the glows. Shorter period, and on restart it sounded much better, but it took a good long while for it to settle down. But the battery was done, it could not have made another restart. And if left outside in that condition, discharged, it would freeze and bust. Dont think for a minute a Bus is any different.

 I swore I would never do that to an engine ever again. But I have. I tried it on a couple Ford trucks and they didnt like it either. That is really a mean thing to do to an engine you like. There is a reason they put heaters on diesels, and we should use them. I would argue to plug in anything below 40F on an indirect injection diesel (prechambers), and anything below 30F on direct mechanicals, at least anhour before you want to start it, longer as it gets colder. I always feel around the engine for warmness. If its cold, wait. Adding to much extra throttle when its cranking works against you too, your just putting more cold fuel into something that dont want to burn in the first place.

 I dont like ether for starting ice cold engines either. A diesel in good shape will start under proper conditions without a bunch of BS. Trying to force them to run when they dont want to (arctic cold/unheated engine) is asking for trouble IMHO. Plug them in and wait. Cracked heads, bent valves, broken pistons, bent rods, broken cranks, are the result of forcing things too hard when those parts are frosty freezing cold. Using it to start a not so cold engine just to get the thing running after it ran out of fuel is another matter.

 Unless the thrust bearing is pressure lubricated, rather than oiled from main bearing runoff, I cant see it being any different than any other engine. Pressing the clutch and cranking the engine shouldnt cause trouble to the thrust unless perhaps its continuous and excessive. But again, if the engine has the proper conditions to start, its gonna just pop off instantly and you dont need to push in the clutch. As you hear so often, many times these things are running on the second turn. Thats how they should start. Ifthey have to crank and crank, either they arent getting fuel, something is mechanically wrong, or they are too cold.

 Whats the coldest anyone has seen a Detroit light off without heat or chemicals?

[HB of CJ]

If you have no block heater or ether, try pulling the OUT TO STOP cable, (if you have one) then crank the cold engine over without pushing on the gas pedal and without pushing in on the clutch pedal.  Crank it for about 30 seconds.

Then push the "PULL TO STOP" lever in while pushing on the gas pedal once, then release the gas pedal and crank the mill to start it, again without gassing the gas pedal or pushing in on the clutch.  Tranny must be in neutral.  This first builds up some heat in the heads and combustion chambers without adding any fuel.

Leaving the tranny in neutral without pushing in on the clutch adds rotational mass to the engine by spinning the very cold gears in the tranny.  The engine may spin very slowly at first, but as it builds up heat, it will spin faster and faster.

Only cranking 30 seconds at a time keeps the starter from overheating, something that is possible even when it is very cold outside.  If the engine doesn't start on the second try, pull out the "PULL TO STOP"  lever and crank again for 30 seconds.

Wait about 1 minute between attempts.  It might take multiple attempts to start up your very cold mightly Detroit and good batteries are necessary.  This technique works if you don't have either a good block or coolant heater and no ether either.

If you have no pull to stop lever, (lots of installations on the newer stuff do not) you will have to go to the engine compartment and pull the rack manually back to the no fuel/stop position.  I do not know if this is possible with the DDEC engines.  HB of CJ (old school old coot)

[kyle4501]

Yep, if the engine is in good condition, it will start easily. However, the 2 stroke will continue to "git 'er done" long after it is past 'good condition' & for those of us who don't use them enough to justify an immediate rebuild, difficult cold starting is something that can't always be avoided. So, the block heaters are definitely necessary. A heater for the transmission wouldn't be a bad idea either.
I'd expect the pressure on a bus clutch would be significantly higher than that of a car, but I don't know.

If all the glow plugs were working, I never had a problem starting my MB 5 cylinder diesels. The battery in those cars is huge for a car.

If the block heater was plugged in, they fired off like a normal warm start.
If not plugged in (- like after working all night) all I had to do was fire the glow plugs once or twice & then crank the engine till it was firing evenly - as per the owners manual. -If it ever ran rough after a cold start, I knew I had a bad glow plug or two.

I never once replaced a starter, but glow plugs & fuel filters were something I kept on the shelf. 

[Fred Mc]

My 8v71 in my GMC 4106 has a special "port" on the blower for ether. I'm sure that wasn't only for starting when you run out of fuel.

[TomC]

As to the thrust bearing in the engine, it is interesting to note that the ONLY was you can start new trucks is by depressing the clutch first.

To start a cold 2 stroke Detroit, do it from the rear.  Turn on the ignition, then with your fingers (works better with gloves) hold the stop lever in the stop position.  Start cranking the engine still while holding the stop lever in the stop position.  Count to 5, then while still cranking, slowly release the stop lever and the engine should just come up to idle.  This retards the timing on the injectors making cold starts easier.  Good Luck, TomC

[buswarrior]

Temperature extremes highlight all the bad maintenance.

Have a habit of leaving the fuel tank partially empty while parked?
water in the fuel is not your friend in sub-zero.

In the cold, batteries and connections are KING.

Cleaned all grounds AND positive connections? at both ends?

Cables in good repair?
How old are they and where is the creeping green and black plague hiding?

Are the batteries in good condition and is there a way to keep a full charge in them when parked?

In the cold is too late... that's why you take a pleasant afternoon in the warm weather to do your preventive maintenance and system installs, so you aren't screwing around with frozen fingers now...

Pushing in the clutch can make the difference between a start and being unable to provide the service. Removing the transmission bits from spinning in their soupy cold lube can make all the difference in the speed of rotation...

Of course, taking other prudent steps to ensure a warm start reduces the level of excellence required in your systems and methods...

happy coaching!
buswarrior

[robertglines1]

has the blower flapper tripped?

[challenger440]

Hi everyone.  The bus (7) starts OK.  but it takes a little more cranking than I'd like.  Last time I started it was about 45f.  Engine spun fine but took 3 attempts (ten second bursts)and one small shot of  ether.  Most likely would have started w/o the ether, but I was leary melting my starter.  On the second start attempt there was white smoke but you could feel that it just did not want to go.  Third go it started but was a little reluctant at first.
   Our diesel tractors have glow plugs of one sort or another.  And they are always plugged in during cold weather.  Cows would be most unhappy with out dinner.  But since the 71 does not have glow plugs, that's what prompted my question.  I'll try starting from the back next time and see how that goes.   Thanks, JM

[Madmike]

Mine does the exact same thing. I think the white smoke is from the Either. Below 50 i give it a shot and then she comes to life. The coldest i have done it is around 4 and it took me a couple of times.

[Lin]

The block heater makes it so easy that it feels like cheating.