Engine problems?

[AMGeneral]

Well,got the grill and radiator out of the way on the 10 ton today,hooked up the batteries and slave off the 816 and the Deuce.I spun it over with a 3/4 drive rachet first (to make sure it wasn't hydro locked)spun it over with the starter for a total of about three minutes and it won't fire,even off starting fluid.I am getting fuel from the return line to the tank though.I'm gonna try again tomorrow with freshly charged batteries,hopefully it'll light off.

 

[westfolk]

Sounds like I'm not the only one trying to get a beast running. Though you have a bigger one. Mine is only an M52A2. At least you're getting return on the fuel I'm not getting that yet. Since it won't fire even with ether. How long has it been sitting? Chance the valves are stuck. Had that on another engine that was only sitting for a couple years.

 

[AMGeneral]

According to everyone I talked to,about 10 years.Valves are a possibility,Imay pull the valve covers tomorrow.This could very well be what's wrong with the Mack engine in my M52 as it runs but misses.but it comes and goes plus it has a new injection pump and injectors.Come to think of it I never got ANY white smoke out of that 903,even with the ether.

 

[westfolk]

Yeah, I'd check that. What I like to do is have someone else run the starter so I can sit right there and eyeball each valve. Then if I have to take the rockers off I like to run right down the line of valves. Tapping each one and spraying WD-40 down the stem. That way it gets them loosened up good. I figure if one or more is sticking it can't hurt to help out the other ones.
Sounds like the Mack engine may have a valve that's sticking when it feels like it.

 

[DDoyle]

AM General,
My M123A1C won't start without using the hand pump in the cab - instructions for use on the dashboard. Also, the starter should really whirl the big Cummins around....loose connections will make it turn slow, and not fire.

Hope this helps,
David

 

[WillWagner]

AM General,
Does your 123 have a 903? If so, if the valves were "stuck", they'd be bent now. No room in the cyl. when the piston is at TDC. Check to see if there's fuel out of the F/P at the solinoid. If not, there's a little knurled screw at the front of the FSOV. Turn it in 'till it stops. That's putting the pump in manual...it won't shut off with the switch if it lights, just turn the screw back out and it will shut down. It's normal for fuel to be at the return line of the pump, that's the cooling line.. it's there so you don't snap gear pump shafts on decel.

 

[AMGeneral]

Will,I'm not sure if it has a 903 or the earlier 785 ci Cummins.I have worked on the 1710 Cummins(V12)are these similar?Being as I barred the engine over by hand(very slowly)It would have stopped turning if the valves were stuck in the open position wouldn't it?I wouldn't think I was strong enough to bend or snap off a valve.I tried the override on the solenoid yesterday,I think it may not be turning fast enough.Shouldn't it have a battery cable running from the neg- batt post directly to the starter ground?

 

[cranetruck]

Guys, according to 206-20, the M123A1C has the Cummins V8-300.
785 cubes, 300 hp.
Let me know if you need any other info.

The engine (V8-300) manual is TM 9-2815-213-34.
Clutch is Mack model CL-50.

 

[WillWagner]

Nah, 1710 is basically 2, 855s stuck together, 903, same bore as an 855, shorter stroke and a PITA to work on....well i guess kinda the same! Rule of thumb, 150 to 200 RPM to make it start, but they will start with less, just takes a bit longer. If it had a bent valve, you'd hear it. A chuffing sound out the exh, or a popping noise in the intake and it would be very easy to turn over. Did you loosen or take the line off at the FSOv outlet and see fuel? If it's been sitting 10 years, the plate in the FSOV...fuel shut off valve... could be varnished or alged to the disc. Check the resistance on the coil, 7 ohms for 12VDC and around 16-18 for 24VDC, Maybe the coil is so swolen it won't work on manual or with battery voltage

 

[WillWagner]

Same applies to the V-8 300..except it's not 5 1/2 bore! Fuel system is the same type, just a different calibration.

 

[Massm35a2]

Got engine pics yet, I want to see what is under the hood of that beast

 

[WillWagner]

A medium sized Cummins V8, Air compressor and fuel pump down in the valley, and if it's turboed, thats sittin on top of the engine.

 

[AMGeneral]

Well,cleaned all batt and starter connections+added a second ground cable from the frame ground directly to the starter ground.It did turn over faster,just not fast enough(75 rpm maybe).I think i'll have to get two more fresh batteries and try with a larger set of jumper cables to the 816.Interesting note,Idid have a chuffing sound from the exhaust,but found out they were both full of water!!Sometime in the past someone had put dual vertical stacks on the truck without caps.Took off the mufflers and the chuffing sound went away,I'll keep trying.

 

[AMGeneral]

Tried again today,4 4LDT batts in series parallel,getting fuel out of the FSOS getting fuel out of the return line from the heads,still no fire.The engine still will not fire off of ether,or anything else for that matter.It still may not be turning fast enough,I guess I need to pull off the starter next and see if it is dragging.I haven't noticed any metal to metal contact noises when turning the engine over though so I guess thats a good sign.

 

[DaveP]

maybe towing it would work. sure would turn over faster.

 

[timntrucks]

seams like you have done all that i could think of , please keep us posted with your steps and progress

 

[JDToumanian]

The most baffling part to me is that it won't fire on ether. The only explanation I can think of, other than zero compression (which I'm sure you would have noticed!), is that the ether is simply never making it to the cylinders, which I would think means air is never making it to the cylinders, either.

I've had engines with dead injection pumps running (albeit poorly) on only a light mist of ether sprayed continuously into the intake - no fuel from the injectors at all.

It's possible that there is an emergency shutdown flap somewhere on the intake manifolds or near the turbo, and that it is tripped. Detroit Diesels have them, the guys call 'em "mouse traps", because they have a little spring loaded catch. Once you pull the emergency shutdown cable from the cab, the engine will not get any air until the flap is manually reset from the engine compartment.

Other than that, I'd be checking for some other air intake obstruction. If you can smell raw ether coming from the exhaust and the engine will not fire then I would think it's got serious problems!

Good luck, let us know!

Regards,
Jon

 

[DDoyle]

Are you using the hand priming pump on the dashboard? - If no, it probably won't start.

Are you using jumper cables, or a slave cable? If jumper cables - it probably won't start.

Is the air filter hooked up? If so, ether won't help.

Pulling the starter from one of these is a MAJOR undertaking - especially it its not been done before. Before doing that, I'd urge you to pull the hot batteries from your 800 series and actually install them in the ten ton (much better connetion - much better current - than with jumpers or slave).

If you do decide to pull the starter, and the sheetmetal is on the truck - you'll need enough extensions to essentially reach the length of the block.

If, as someone suggested, you pull it to start - remember - you have NO brakes....and, don't rely on the truck building air on its own initially. Once you get the engine running, if no air, remove and polish the little air compressor valves, they are prone to corroding and hence not sealing, on these trucks.

HTH,
David "been there, done that" Doyle

pulled and replaced M123 starter
rearended by M123 being pulled to start
had M123 with no air pressure
fought hard to start M123 for months - bought four new batteries, now it fires right up.

 

[AMGeneral]

Sucess!!(sort of),got the 123 fired today about 6 pm.I wasn't pleased by the sound at all though.Lots of metal to metal noise high in the engine,needless to say I didn't run it long(30 sec maybe)Had oil press,about 45 psi.So next step is,pull cylinder heads and investigate the problem.Actually I believe I'll go ahead and check everything while I'm at it,bearings,cam,basically do a complete inframe,that'll give me a good starting point.

 

[texas-5-ton]

Hey General,
Glad to hear that you were able to breathe some type of life back into that ol' hoss. I'm not suprised that it made some racket, especially after sitting up for 10 plus years. I am confident that you can find the problem and make it purr like new again. Keep us posted on what you find.