Bus Conversions dot Com Bulletin Board
July 28, 2014, 01:33:34 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
News: If you had an E-Mag Subscription: You can zoom in to make the text larger and easier to read.
   Home   Help Forum Rules Search Calendar Login Register BCM Home Page Contact BCM  
Pages: [1] 2 3   Go Down
  Print  
Author Topic: Engine start question  (Read 3460 times)
Chaz
Hero Member
*****
Offline Offline

Posts: 1508


4108, 8V71 w/auto .


WWW

Ignore
« on: May 14, 2007, 11:17:43 AM »

Ok, I know I need to do a little more work to my motor, but I'm trying to give myself a little hope here.  Undecided
  I had the rack run this past winter and that was fine, but the ol'girl still doesn't like to start without a shot of ether or have the motor plugged in............ and it's probably about 80 degrees outside and she needed a little bump of ether.    Bummer, huh.  Sad
  The next thing- the guy who ran the rack for me said- was to compression check it and then maybe put in new injectors and bench them.
   My question is: could the injector work help with the starting issue or is it just plain and simple that I need the bottom end gone thru? Just trying to give myself a little hope, but I'm afraid I already know the answer.   Cry  Cry Cry Embarrassed
  What's you guy's profession opinion  Smiley and experience say??  I can take it. Cry Cry Cry Cry

   I start hard in the mornings too,
      Chaz
 
Logged

Pix of my bus here: http://s58.photobucket.com/albums/g279/Skulptor/Motor%20Coach/
What I create here:   www.amstudio.us
 
"Imagination is more important than knowledge". Albert Einstein
WEC4104
Hero Member
*****
Offline Offline

Posts: 779





Ignore
« Reply #1 on: May 14, 2007, 11:30:33 AM »

First off, can you answer a few more questions? 

1) How's your cranking speed when you are trying to start? 

2) What can you tell us about your exhaust smoke?  Smoking for a bit, in the first few minutes after start up?  How quickly does this clear up?  What about smoke in the exhaust once your are up to temp and cruising?  Smoke color?

WEC4104
Logged

If you're going to be dumb, you gotta be tough.
Dreamscape
Guest

« Reply #2 on: May 14, 2007, 11:48:51 AM »

Chaz,
I had a similar problem with my 8V71. Got rid of a couple of bad 8D's and installed a couple of brand new group 31's. I think the problem was the 8D's just did not spin the ole Detroit fast enough. Since I have had the Group 31's it cranks much faster and has started each time very quickly.
I hope this helps a bit, I know how frustrating these monsters can be at times.

Happy Trails,

Paul

Dreamscape
Logged
Chaz
Hero Member
*****
Offline Offline

Posts: 1508


4108, 8V71 w/auto .


WWW

Ignore
« Reply #3 on: May 14, 2007, 11:56:18 AM »

Quote
1) How's your cranking speed when you are trying to start? 
Seems to be good. I have 2 new 8d's and I even checked them to make sure.

Quote
What can you tell us about your exhaust smoke?  Smoking for a bit, in the first few minutes after start up?  How quickly does this clear up?  What about smoke in the exhaust once your are up to temp and cruising?  Smoke color?
Smokes pretty much in the beginning and for several minutes, but clears up. About 2 blocks down the road it's fine. You can just barely see the exhaust. In the beginning it's basically white or at least very light colored.

Quote
I had a similar problem with my 8V71. Got rid of a couple of bad 8D's and installed a couple of brand new group 31's. I think the problem was the 8D's just did not spin the ole Detroit fast enough. Since I have had the Group 31's it cranks much faster and has started each time very quickly.
I hope this helps a bit, I know how frustrating these monsters can be at times.

  Thanx Paul. I'm not even sure how fast it should crank, but I would hope the 8d's would do ok.

    Chaz
Logged

Pix of my bus here: http://s58.photobucket.com/albums/g279/Skulptor/Motor%20Coach/
What I create here:   www.amstudio.us
 
"Imagination is more important than knowledge". Albert Einstein
Stan
Hero Member
*****
Offline Offline

Posts: 973




Ignore
« Reply #4 on: May 14, 2007, 11:59:40 AM »

Chaz: If it is not cranking fast with new batteries, then you may have a dragging stzrter.  You need to hear one that cranks properly to evaluate your own.
Logged
Dreamscape
Guest

« Reply #5 on: May 14, 2007, 12:01:51 PM »

Chaz,

Diesel fires under good compression. At least that's how I understand it. The faster the crank the higher the compression build up. I am sure some else has better understanding of how it all works. I do notice mine spins a lot faster than it used to. I also rebuilt my starter and replaced some cables.

Paul
Logged
JackConrad
Orange Blossom Special II
Global Moderator
Hero Member
*****
Offline Offline

Posts: 4446


73' MC-8 8V71/HT740 Southwest Florida


WWW
« Reply #6 on: May 14, 2007, 12:18:22 PM »

Chaz,
   As was mentioned, diesel ignites from the heat of compression. To generate enough heat from compression requires enough compression of the air which is dependent on a couple factors. First no or very little leakage of the air from the cylinder (bad rings, leaky valves) and the engine spinning fast enought to compress the air quickly enough to get the neccessary temperature to ignite the diesel.  Someone else may toable to expalin it better or in more detail. I am sure there are probably other factors, I have overlooked.  Jack
Logged

Growing Older Is Mandatory, Growing Up Is Optional
Arcadia, Florida, When we are home
http://s682.photobucket.com/albums/vv186/OBS-JC/
skipn
Guest

« Reply #7 on: May 14, 2007, 12:40:59 PM »

Chaz,

   As Stated injector or valve or rings or starter speed or any combinations so some diagnostic tips FWIW

 Poor injectors tend to have a real knocking sound when the engine first starts up and will quit once warmed up or even quicker.
 Rings open the Oil filler if the rings are really bad you can actually hear a slight popping sound (really bad) a lot of air can mean worn rings.
 Valves ( a little harder to tell) at a warm bumping the throttle is there a tint of blue with the black (really hard to see).

 Any one of those conditions can cause hard starting.
   If you remove the injectors to be tested (best diagnostic) do a compression test then you will know for sure.

  JMO
  Skip
Logged
Chaz
Hero Member
*****
Offline Offline

Posts: 1508


4108, 8V71 w/auto .


WWW

Ignore
« Reply #8 on: May 14, 2007, 12:54:55 PM »

Ok so......... can injectors cause it to need ether or a block heater? If not, I'll just scrape that idea and hope for something like the starter not turning fast enough or something like that. I will be going to a bus ralley in Cincy next month so I can hear how fast one starts there I guess.

  But.................... it's my guess the ol'girl is just weak. She does run pretty good tho, and I'm told to just run her, but I just like to have things operating as best as i can.

  Thanx guys,
      Chaz
Logged

Pix of my bus here: http://s58.photobucket.com/albums/g279/Skulptor/Motor%20Coach/
What I create here:   www.amstudio.us
 
"Imagination is more important than knowledge". Albert Einstein
larryh
4905A-893 P8M
Sr. Member
****
Offline Offline

Posts: 350


ready to run with the big dogs




Ignore
« Reply #9 on: May 14, 2007, 01:06:02 PM »

Chaz

Your injectors can be worn or partially clogged up or just wearing out you can pull the injectors and have them flow tested and that will show the spray pattern if they are not atomising the fuel you will have starting problems thus taking ether to fire her off. If starter is pulling too many amps a snap on the batt cable meter will show you how many amps your starter is pulling.

There is more to starting a diesel than just a charged up battery so I would say a good electrical test is first order then if you need a flow test on injectors then a perfect time to do a compression test when inj are out.

Hope this helps.

LarryH
Logged

Savvy ponderable:
A cowboy's only afraid of two things:
havin' ta walk,
and the love of a good woman.
"This posting was generated using an environmentally friendly, self contained flatulence generator, therefore no fossils or neutrons were harmed in the creation of this posting.


Quartzsite,
skipn
Guest

« Reply #10 on: May 14, 2007, 01:31:15 PM »

Chaz,

   OF course start with the easiest to fix diagnose etc. first. Starter thing...

  Bad injectors can make it very hard to start an engine. Weeping, poor spray pattern etc injectors can cause
 a lot bigger problems down the road if they are not fixed. A weeping (solid stream popping off at less than spec pressure) can
 eventually burn a hole in a piston. That is bad.

 Just some info for thought.
 Skip
Logged
Chaz
Hero Member
*****
Offline Offline

Posts: 1508


4108, 8V71 w/auto .


WWW

Ignore
« Reply #11 on: May 14, 2007, 04:37:03 PM »

Thanx guys!!!!!! I appreciate the info. I will start with the amp draw. (a buddy owns an auto repair and should have that equiptment) Then I may have the injectors gone thru and a compression test anyway. The more I think about it, the more I would just like to know. But hopefully it won't be as bad as I think. But......................................................... Undecided

   Thanx again!
      Chaz
Logged

Pix of my bus here: http://s58.photobucket.com/albums/g279/Skulptor/Motor%20Coach/
What I create here:   www.amstudio.us
 
"Imagination is more important than knowledge". Albert Einstein
skihor
Sr. Member
****
Offline Offline

Posts: 290





Ignore
« Reply #12 on: May 14, 2007, 05:20:51 PM »

My 6V92 can set for a month and I can't hit the starter button fast enough. It starts before 1 revolution...  When it's cold I plug in the block heater for a couple of hours and it starts the same, pretty much instantly.
Good luck,

Don & Sheila
Logged
Jerry32
Hero Member
*****
Offline Offline

Posts: 726





Ignore
« Reply #13 on: May 14, 2007, 06:43:15 PM »

I have an old gm with a 8V71 that had been setting for some time and once the starter was engaged it burst to life with enough smoke to run everyone off. Most will start on the first rev or so. batteries can't get the current to the starter if you have a bad connection.make sure your grounds are good at all points and then a voltage chec while cranking at the starter could confirm if there is a large voltage drop. A dragging starter will draw more current and show a larger voltage drop.  Jerry
Logged

1988 MCI 102A3 8V92TA 740
TomC
Hero Member
*****
Offline Offline

Posts: 6677





Ignore
« Reply #14 on: May 14, 2007, 08:00:40 PM »

Chaz- I have a fresh 8V-71N (now turbo'd).  But when I was at Grand Canyon last year about this time, it got down in the 30's and we sat for two days.  I opened the rear engine door thinking I might need ether.  I started to turn it over and it fired in about three revolutions with a big white cloud that disappeared in about one minute of idling. 
If the injectors are not up to snuff, you'll get alot of black smoke before it fires (dumping raw fuel that is not atomized very well).  If your rings are worn (which this sounds to me) then you might be able to get by with just replacing the piston rings and bearing shells if the cylinder liners are not worn excessively (if you can see the hone marks). I would get it done soon since worn piston rings can break since they are thinner.  Good Luck, TomC
Logged

Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Pages: [1] 2 3   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.18 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!