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Author Topic: Pneumatic vs. 12vdc starters for 8V71...  (Read 1924 times)
OneLapper
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« on: June 24, 2013, 11:11:10 AM »

Fellow 8V71 owners;  How many are using pneumatic or hydraulic starters?  How many of us bus owners replace the 12vdc starters on their 8V71's every other year?

I'm now on my fourth starter in 7 years.  I just had a shop rebuild it for $181 and I'd say that was the average price ($150 to $225 has been the cost range).  I decided to use a different shop to rebuild it this time, but I'm seriously considering an air starter.  I don't know much about them, what pressures they need, the size of the tank, hose, etc. but with an average annual expense of nearly $100 solely for rebuilding starters, the break even point probably isn't that much of a stretch.  That doesn't even take in account the time and effort to replace the starter, which on a 4106, is not an easy task!

To address some of the obvious issues, I have replaced the OEM battery cable with 0000 cable.  I replaced the starter to block ground with 0000 cable.  I replaced the block to frame ground with 0000 cable.  I then ran a 00 ground cable from the frame ground back to the battery just to be paranoid.  The cables were made using a hydraulic crimper and double wall heat shrink tubing over the cable jacket and the lug connector.  The cost of the cables were most likely more than a pneumatic starter!

I do use the bus in the winter.  It's rare that I need to start the bus without having the opportunity to plug in the block heaters, but I would have to say that two or three times a year I need to crank the engine over for a total of 60 seconds to start it.  The engine runs great and it starts easily even in the mid 40s to low 50s.  Am I asking too much from a 12vdc starter?

 
« Last Edit: June 24, 2013, 08:47:09 PM by OneLapper » Logged

OneLapper
1964 PD4106-2853
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Lee Bradley
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« Reply #1 on: June 24, 2013, 11:20:28 AM »

Seems like a lot of rebuilds.  Which model starter?  Maybe a bigger model? Or a Japanese gear reduction starter? I don't know that I would go
with air without an air compressor on broad.  I remember a EMD 20V-710 with air starters that had a shop air compressor with a gas powered
air compressor as a back-up.
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luvrbus
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« Reply #2 on: June 24, 2013, 11:25:59 AM »

Bad rebuild or a possibility someone over the years has replace 42 MT with a 37 MT the 42 is good up to 14L and the 37 up to 8.3L check the tooth count it makes a huge difference  

To bad for lefty owners no one makes the 39 you can hold in one hand it was design for us old guys seriously the 42 starter doesn't give any problems unless wrong tooth count and low voltage next if you can move the batteries closer to the starter the 42 should out last the bus
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OneLapper
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« Reply #3 on: June 24, 2013, 11:33:35 AM »

I should have mentioned that I didn't have the same starter rebuilt each time.

I carry a small 110vac air compressor that can run off the inverter.  It would be straight forward to use that to build up pressure in the air tank. 
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OneLapper
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eagle19952
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« Reply #4 on: June 24, 2013, 11:38:31 AM »

The pneumatic can use up a lot of air...a real lot.
Something is not right...
follow-up on Clifford's post...
try a different rebuilder....?
have you tried a new starter...?
a new rebuilt by Delco....?
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OneLapper
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« Reply #5 on: June 24, 2013, 12:13:20 PM »

All the starters have been 'spares', take offs from two engines I scrapped, plus a spare that came with the bus when I bought it.  The original starter would die when hot so I had the spare that came with it rebuilt and installed that.  Then that went bad and I had the original starter rebuilt.  Then I used one of the take offs when that crapped out.  Now I just had the second scrapped engines starter rebuilt to replace the weak starter that nearly left me stranded at the SAME fuel pump I was stuck at four years ago!   I have no idea what model starters they are.   I'll take a look tonight, I haven't installed the starter I just had rebuilt last week. 

Clifford, how many teeth should the right starter have? 
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OneLapper
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Iceni John
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« Reply #6 on: June 24, 2013, 12:30:08 PM »

FWIW, my experience with hydraulic starters is such that I wouldn't consider them my first choice in a bus, especially an infrequently-used private bus (as opposed to an intensively-used bus in commercial service).   Many years ago I worked on gas production platforms in the North Sea, and both our lifeboats had hydraulic starters for their little diesel engines..   If the engines didn't start on the second or third try, there was no more hydraulic pressure left.   At that point someone (usually me) had to manually crank a pressure accumulator pump about a million times to build up sufficient pressure for another try at starting.   That was bloody hard work, and it took at least ten minutes.   No fun.   Just imagine doing that while everything's on fire around you, or worse  -  remember Piper Alpha?   Maybe those old hydraulic systems leaked down, or perhaps the boats' engines were past their best, but I thought at the time it was a dumb way to start an engine in an emergency situation.   Heck, we could have got further away from the platform in less time by putting down into the water and then just drifting away from it with the current!

A year or so ago I moved my starting batteries much closer to the engine.   Using the same batteries, starter and the same 4-0 cable but much shorter now, my engine now starts noticeably better.   Maybe that's the solution for you.   Have you checked what voltage your starter is getting under load?

John
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« Reply #7 on: June 24, 2013, 01:04:39 PM »

Air starters are mainly for boats and trucks where weight is more important. I once was on a crew boat that had 3-12V-71TTI's, 2 2-71 generators. Only one of the generators had an electric starter. All others had air-which wasn't a problem with 2-7.5hp air compressors on board.

Rather then spend all the time, money effort to switch over to an air starting system (the air tank takes alot of space), spend the money and buy a NEW starter with new starter warranty. It will most likely last the rest of your life. Rebuilds never will see the same life as a new starter-except if a new armature is installed in the rebuild. Good Luck, TomC 
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OneLapper
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« Reply #8 on: June 24, 2013, 01:07:33 PM »

I figured hydraulic wouldn't be the right application for a bus, especially wight wide temperature swings out buses can experience.  I thought I read here that someone was using a pneumatic stater. Maybe they'll surface and offer some insight.  

I'll check the voltage at the starter, I haven't done that since installing the 0000 cable.  It's possible I've been using the wrong model.  I've never checked that.  
« Last Edit: June 24, 2013, 08:51:07 PM by OneLapper » Logged

OneLapper
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Don4107
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« Reply #9 on: June 24, 2013, 03:11:28 PM »

Drove a Kenworth with a air starter on a 3406.  It exhausted straight down just behind the drivers side front wheel.  Was great fun to start it when someone was standing there talking to you. Boy did they jump from the sound and cloud of dust.  Air tank was as big as the fuel tank and took a long time to charge with a small compressor. You think people complain about the sound of you genset, just try an air starter.

A GM would be challenging to install because it is so tight.  The air line to the starter is the size of your arm and you know how well that fits in there.

If you are cranking for 60 seconds without a break don't expect the starter to live very long.  If it's only in cold weather use a little starting fluid.  That's what these thing were designed for.  That's why they have a cup build into the intake.  Yea, Yea, I know even a drop of starting fluid and it is sure to blow up.  I said cold, are we clear on that!  If it does not start without block heat, it is cold enough for starting fluid or the poor thing is just plain tired. Of course there are all the caveats, worn out, turboed low compression engine ect.

Good luck
Don 4107 now 5B
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Don 4107 Eastern Washington
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Dave5Cs
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« Reply #10 on: June 24, 2013, 07:08:11 PM »

Are the GM s all 12 Volt starters?. My MCI is a 24 Volt. Is that maybe the problem?

Dave5Cs
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RJ
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« Reply #11 on: June 24, 2013, 10:17:44 PM »

Mark -

Do you want to totally give up one of your two baggage bays?

That's the size tank it takes for an air starter.

At the transit property I worked at, we had a bunch of coaches with air starters.  I can't tell you how many times when I was working dispatch I'd get a radio call from a driver needing the shop to come air up his starter tank because the coach didn't fire the first time round.  Often by the time the shop got enough air into the tank, the driver was late pulling out of the yard for his morning run.

And if, for some reason, the driver shut the coach off while out on the line, then ran out of air trying to restart, dispatch had to send out another bus to cover the run until the shop could get it going again.

The air starters were eventually replaced with electric. . . far more reliable in transit operations.

I tend to agree with some of the others - there's another problem somewhere else, so perhaps more diagnostic troubleshooting is in order?  (Oh, and it's been recommended that you not run the starter more than 15 seconds w/o a minute or so cooling off period when attempting a cold-weather start.  This also allows some "heat soak" into the combustion chambers to help bring the internal temp up to support running.)


Dave -

Marks 4106 is 12vdc.  The 4905s are 24v.

FWIW & HTH. . .

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« Last Edit: June 24, 2013, 10:19:30 PM by RJ » Logged

RJ Long
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OneLapper
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« Reply #12 on: June 25, 2013, 06:56:29 AM »

Sounds like the pneumatic starter just isn't the practical solution to my seemingly short starter life.  Last night I didn't have an opportunity to look over the starter I just had rebuilt so the model number and tooth count is unknown.  Maybe I'm just hard on my starters.  Like a said, I use the bus year round and have been pretty far north into Canada during the winter several times.  I'll admit those were not easy starts, especially when I needed to bring the Honda suitcase generator into the hotel room overnight to warm up, then used that to run a block heater on the bus generator, then used the bus generator to run the dual block heaters and oil pan heater on the engine.
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OneLapper
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« Reply #13 on: June 25, 2013, 07:46:43 AM »

My question is. How long do you have to crank before she fires. My tired 6v92 starts usually on the first or second turn. During the winter and engine preheated I usully only let it spin a few turns then let it set. After a few trys it will fire up. I'm not in northern Canada. Your starter may be giving you normal life if you have to crank it for long periods before start.

John
« Last Edit: June 25, 2013, 08:00:30 AM by Jriddle » Logged

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John Riddle
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« Reply #14 on: June 25, 2013, 08:05:40 AM »

In the cold country lot's go the 50 MT that heavy sucker will last
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