Oil viscocity and starting the engine

[Paladin]

I went out and put different batteries in the beast and charged them just to be safe ( last time I ran the bus I forgot to throw the master and it drained a different set totally!)
Later I went out to start the beast and it growled, turned over a few times and then acted like the batteries were low. I can't vouch for exactly how good these are but they were good in the fall, I'd say maybe 2 years old?
I plugged in the block heater, waited a couple hours and then tried again and it spun and fired right up.

My question is, even though I'm not certain of the quality of the batteries they did run it before. Does oil viscosity play enough of a role to bog me down like that until it's warmed or might I have a starter that's also drawing too much current or some other gremlin? Previously when I started the bus with no block heater it's been above 60 or so and fired instantly but today it was about 50. seems sort of odd to me that it would bog down that much on oil.   

[Tenor]

Has it been colder than 50 for the last few days?  If today was the first warmish day, the block could still have been very cold.  That's a lot of mass to warm in the winter sun!

[Paladin]

Yes and no and I also thought of that. It's been low 50's during the days but still pretty cold at night. I should have taken a temp of the oil and block before and after. I usually do just for reference. 

[PP]

Hey Pal, I'm not a diesel mechanic, and I'm sure more than a few will pick up on this one in a minute or two, but my experience has always been that a cold engine swings faster than a warm one because there is much less compression in a cold engine. The rings will seal tighter as everything warms up and give you compression. FWIW I'm sorry if this doesn't answer your question, PP

[NJT5047]

Short answer is yes.  A block heater will enable a cold engine to start much more easily.
Depending on how long your batts sat dead, they may be trashed. 
And, depending on what you're charging them with, it may take a couple days to fully charge both batteries.   
Charge'em up until they are fully charged, remove the charger and check the battery voltage after they sit for a few hours...then a couple of days.  If the battery voltage on either battery drops below 12.6 or so...get ready to buy some batteries. 
And all the common sense things such as dirty battery cable/posts...grounds apply here.  Clean everthing...WITH THE BATTERY MASTER IN THE OFF POSITION.   And as you know, always turn the battery master off when you leave the bus.   I turn my cranking batts off even when camping in it. 
JR

[Fredward]

The fact that it started after warming the engine could mean a few things. One as has been mentioned; batteries. I don't know what type of coach you have, but my MCI has about 30 feet of battery cable between the batteries and the engine. So those cables could be an issue and the connections on either end could be suspect as well. (not the battery terminals themselves). Another consideration is the starter. A tired starter draws more current, or rather it requires more current to do its job. Cold weather and thick oil could point out a tired starter.

As a reference, living in Minnesota, my 8V71 will start unassisted using two group 31 batteries down to about 40 degrees F. Below that, it requires ether or block heater. Larger batteries might help. Group 31 is a little small for this starting application.

Also working against you, as you pointed out, is oil viscosity. Straight 40 is the recommended vis and that is some stiff stuff at cold temps. I also have a dipstick heater I sometimes use to warm the oil in addition to the coolant.
Fred

[Busted Knuckle]

That's a lot of mass to warm in the winter sun!

1st off, it takes even longer inside a dark closed engine bay surrounded by cold metal & yes I think it can cool off that much! Our buses do well down to about 30 (unless it's been that way for days and they haven't been started), but we still like to use the block heaters if we know it's gonna get below 40 and we are planning on firing them up in the middle of the night/early AM! As an odd side of this my 60 Series (very tired 60 Series) is harder to start than the 2 strokes! And on top of that the old worn out 2 stroke that sits for months at a time starts the easiest of all of 'm ( & I ain't never used any heater on it!
But as mentoned check those wire ends, battery & starter connections! Also cold batteries will slow things down and sometimes the batteries will build up heat from trying to start it and then waiting a short time and trying it again! FWIW   BK 

[buswarrior]

I wouldn't be worrying about oil viscosity until you go well below freezing, and then the heater of your choice takes care of that.

At 50 degrees, the motor shouldn't care.

The other posters have the list: weak batteries, bad cables(anywhere over their entire length, not just the ends) weak starter.

Speed of cranking is the number one issue to getting these started... or not.
Turning is not enough, you need to SPIN IT!

happy coaching!
buswarrior

[JohnEd]

No!  It doesn't spin easier when it is cold.  The bats drop off when cold and the engine oil vis really slows it down.  Colder is slower.  It needs to "spin".  Gas will start at a crawl but not DD.

HTH,

John

[NJT5047]

I'll tell you how to rule out the whole bus battery cable issue. Since your OTR AC has been removed, you have a perfect location to install a couple of group 31s.  Right on the old AC mount.  Then buy, or have made up, some battery leads and you got a fast turning engine starter. 
You'll need to install some sort of battery disconnect near the engine room batteries.
You can attach the B+ to the big terminal mounted on the frame just forward of the rear engine mount.  Follow the alternator and starter B+ leads and they'll be attached there. 
Ground to the chassis right beneath the AC compressor mount...or any other good chassis ground.   Don't use the cradle clamp bolts for grounds. 
You may wish to verify that the dedicated starter ground strap is indeed installed on the rear of the starter (end cap bolt) and grounded to  chassis.  There's another engine to chassis ground beneath the transmission oil cooler.   
You can keep the front 8d batteries for house batteries, backup cranking batteries, or whatever.  The front master will be "ON" anytime the rear battery switch is in the "ON" position...so the bus will be powered up by either front or rear battery switch.   
If you do the rear battery gig, remember that if you remove the front batteries, be sure and remove the pos battery lead from the battery master switch.  It'll be 'hot' when the front and rear battery switches are closed.  If you have a Vanner, either keep the front batteries, or you'll have to move the Vanner to the engine room.  Not sure a Vanner would get along in the heat of an engine room.
If no Vanner, no problemo. 
Your alternator will easily charge a pair of group 31s parallelled with a pair of 8ds.
Cheers, JR 
BTW, let me add that if you are tapping any 12Vdc off the front battery center, you'll need to leave the front batteries in place and keep them functional.  The only way to pull 12Vdc from the rear batts would require running a dedicated 12Vdc lead from the engine room to the front battery box. Or install a converter.   A PITA.
You may have a tap for the famous 12V headlight backup or a radio source. 
If you have any small leads attached to the 12V center post (Pos term on rear battery), leave the batteries and mark all the leads for replacement in the event you disconnect them, they can be returned to the correct posts.