Engine problems?

[WillWagner]

I've heard them make noise after sitting a long time. Check the filter for metal. If there isn't any there, pull the lids. The injector plungers will varnish together and stick. It makes a whole lotta noise up top if it lights. If they're stuck, that would also explain hard starting too. Check the simple things first, Cummins V8 parts aren't cheap.

 

[DDoyle]

It'd be helpful too, if you have not been around a M123A1 running, make an effort to before you start tearing down the engine. The V-8 Cummins is much noiser than the Multifuel or a 6-cylinder Cummins - as a friend of mine says - they remind him of a threshing machine when running right!

Hope this helps,
David

 

[AMGeneral]

I don't believe this noise is normal,VERY PRONOUNCED HARD knock on pass side bank of cylinders,either # 2 or 4(I could be wrong here).I have heard 903's run before(RT crane at work)and this one sounds like you threw a handful of 1/2 in ball bearings down the intake!I'm planning to pull valve covers first (after ft sheetmetal removal)and investigate further.If I can scrounge up the $ I'm going to purchase 1 in GA that looks to be in a more unmodified state(dual winch model minus engine and trans).Then the one I have now may become an engine and trans donor for it.

 

[DDoyle]

I don't believe this noise is normal,VERY PRONOUNCED HARD knock on pass side bank of cylinders,either.....

Nope, that definately is not normal!

Good luck!

David

 

[WillWagner]

Like I said, Do easy things first. When Injectors stick, they make a VERY loud noise, it can be described as a knock, a bang, a ticker. The engine will miss, rock, snort and I heve heard them back fire! The plungers stick in the position they stopped in, all the way up, down, or anywhere in between. Before you make a decision to overhaul the beast..I'm tellin ya, parts aren't cheap, pull the lids and check the overhead. Try to set it. See where the plungers are at the valve/injector set marks. The city of Newport beach towed one in once. They said it spun a rod bearing. Turned out to be 1 stuck injector plunger, they had beed using it when it happened, yours has been sitting.

 

[WillWagner]

Re read that, hope that didn't sound snotty. I've just been taught to do the easy things 1st.

 

[AMGeneral]

Understand completely Will,I'm definetly going to ck overhead and Injectors first,just trying to throw out all the info to this forum I can.I'm used to working on engines in the 30 liter range(or larger!)usually most of the engines I've dealt with that fail,fail catostrophicly.I would rather not see this 903 with a rod poking through the block if I can help it.I definetly appreicate all the info and opinions,Thanks.

 

[DDoyle]

Just don't walk into the Cummins dealers and ask for 903 parts and expect them to fit the V8-300 in your truck - you'll be disappointed, as many people have been before you.

Regards,
David

 

[AMGeneral]

Let me guess,the V903 in the 123 series has some minor differences that are only for government use,and are not used in any civilian application?

 

[WillWagner]

903 and V8 300 are different. There SHOULD be a data tag in the valley of the engine...under the fuel pump and air compressor. DO NOT use scotch brite, sand paper, steel wool, ANYTHING to remove paint or gunk on the data plate. You will make it so it can't be read. Try brake cleaner 1st and just lightly rub it. If it's painted, use gasket remover. Spray it, let it sit for 30 seconds and wipe it off. If that doesn't do it, just keep it up with the gasket remover, it will eventually clean it off w/o damage. Give me the engine sieral number, and i will tell you exactly what it was built as.

 

[DDoyle]

As Will said - the engine in a M123A1 is a V8-300 785 cid engine. It is similar to the V8-300M marine engine, which is a naturally aspirated version of the VT8-370-M. These predate the 903, and, obviously have a smaller displacement. This is a result of a smaller bore. As I recall, there are additional differences as well. Though the military used the 903 in some marine applications, they were not used in the 10-tons.

Hope this helps,
David

 

[AMGeneral]

Well,got the pass side inner and outer fender off today,got the valve cover loose only to discover that it won't come past the P/S resevoir.Cranked it over again,just for the heck of it and the tapping noise seemed much less pronunced.It also seemed to turn over much easier today,it started in about 10 sec cranking without ether.So tomorrow i'll pull the P/S resevoir and see if there may be a injector stuck.It does pour out billowing clouds of smoke while running,and seems to have a lot of blowby.

 

[DDoyle]

The billowing clouds of smoke are nature of the beast with the M123A1 - and I have been around several, so don't be too concerned about that.

Regards,
David

 

[WillWagner]

Keep going. If they are stuck, sometimes you can just pull the plunger out, scotch brite/WD40 them, put them back in and give it a good tune up, and it is good to go. Make sure the push tubes aren't bent b-4 you tune it up.

OH yeah, do them 1 at a time so the plungers don't get mixed up. It matters 'cause the barrel and plungers are a matched set. Use ATF for lube when you put the plungers back in.

 

[AMGeneral]

Well folks,I know this is a old thread,but rather than starting a new one,I'll just add to this one.

I FINALLY(after 3 years) decided to tear back into the 10 ton,pulled all pass side injectors and cleaned em,set all the injectors,valves and crossheads(some of em were WAAAAAYYYYY off), and cranked it over,it fired much easier with lots less noise on the pass side of the engine. I also noticed a serious reduction in white smoke from the pass side exhaust,hopefully a sign that it's firing on all four in that bank.

If the weather is decent tomorrow i'm gonna pull the drivers side fender and repeat the process on that side.Hopefully tomorrow evening will see the big Cummins running as it should,Stay tuned !!!!

 

[AMGeneral]

Well,a minor setback today,seems the 4 injectors on the left bank are really crudded up,as in it may take a professional to get em clean. Managed to get #5,6 and 7 decent(nice 6 way spray pattern) but #8 is basically stopped up(no spray at all) so we'll see how it goes this week.

 

[papabear]

You'll have that thing purring like a kitty soon AMG...I have confidence in ya

Once you get that injector right she probably just needs to be run a little to get everything lubed up etc.

 

[timntrucks]

i am pulling hard for you to get it running right as rain.. please take some more pics and post them