Question for you large diesel mechanics

[Crash_AF]

I have a problem with one of the engines at work and need some advice on how to correct it. The engine is a NTH 'Big Cam' on a diesel fire pump. We can't get it to start and are running out of ideas.



It was running like crap before and one of the guys in the shop tried to adjust the valves and it hasn't run since. It's getting fuel (at least from the pump... ) but I think the injectors are out of adjustment. Does anyone here know the proper way to adjust them because according to Cummins, the procedures have changed since our book and we don't have the new one (and we are out of money until the next fiscal year).



Thanks,

Joe

 

[nickleinonen]

does this engine have the pt pump?

 

[csevers]

some thaughts

If memory serves me right the old big cam engines had top stop injectors/ the new one n14 m11 are adjusted at the bottom of the stroke of the injector seting total travel the old big cams top stop are adjusted at the top for pre load on the injectors some thing like 6 or 8 inch pounds holding up the color around the stem of the injector the vavles are lap timed I and E on one or six and I or E on others but not both on the same cylinder at each mark on the assecory drive pully / new n-14 both valves and injector on the same cylinder at each mark on the pully cummins has changed the procejure on other engins too. If this helps great if not totally disregard I never said a word it has been a long time since I worked on a big cam. Other things to check is power to the shut down seloniod and fuel pressure or maybe this thing has the PACE fuel system on it don't know to much about that the bad thing about fleets is the vehicle are only 5 years old you are always working on new crap and the old stuff gets sold can't keep up with all the changes IF I AM OR WAS WRONG OR FOUND TO BE WRONG IN THE FUTURE THIS MESSAGE WILL SELF DESTRUSCT NOW!





GOOD DAY

 

[A Johnson]

Tell me the CPL # off of the data tag, this will help me figure out what would be the easiest method for you to use. I will then attempt to explain it.



The older NT engines you could set injectors at the bottom of the stroke to 72 in lbs and 14-27 on the valves. You can also do this with some of the STC engines depending on CPL ,although the injector torque specs are different.



Some of the STC engines have a goofy overlap on the valves and it is easiest to set topstop method.



It could be possible your man followed correct procedure but if someone put the acc drive in out of time, when he set the overhead it got all messed up. (Allthough they will usually run, just not run good. ) I can also tell you how to check for out of time acc drive if interested without removing anything but the valve covers.



The CPL # will help me sort all this out. Sorry I didn't see your post earlier, I usually cruise the 12 and 24 valve forums.



A Johnson

 

[Crash_AF]

Thanks for the help,

It's an NTA855F build date 11/87 CPL 0551



Yes, I'd like to check that accessory drive timing also if you don't mind.



Later,

Joe

 

[A Johnson]

Message recieved. Will try to get back to you this evening by 2100 hrs PDT. On Call for work and pager going off too frequently for comfort. Mostly motorhome people.

 

[A Johnson]

Joe, this appears to be pretty much a standard 855 industrial engine with no variable timing involved. So it is pretty easy.



To check for acc drive out of time, put a 3/4 socket with about a six inch or longer extension on the Injector locknut of # 5 cylinder.

Bar the engine over with a 1-5/16 socket on the acc drive until # 5 injector rocker lever just starts to move, at this point the A or 1-6 timing mark should be about 1/2-1inch before the timing pointer cast into the gear housing. If it is within 1/2-1 inch before then your acc drive is in time and you need to use the timing marks on the accesory drive for your overhead setting procedure. If not then I would mark the front cover at this point (where #5 injector lever just started to move)with a paint pen as being the A 1-6 timing mark. Move the socket and extension to #3 injector locknut, bar over until #3 injector lever just starts to move, this will be approximate for the B 2-5 timing mark. Move socket to #6 and bar over when it starts to move this will be the C 3-4 timing mark.



As you can see we are just watching the next injector in the firing order, when it starts to move we are assured that the Injector that we want to set is at the bottom of its sroke.



OK, now for the set procedure.

When on A 1-6 timing mark ( or the new mark you may have painted on the acc drive pulley) Set the injector to 72inlbs, intake valves to . 014" and exhaust to . 027" set the injector before setting the valves. Mark the injectors and valves that you have set so you don't get lost.



Procede thru the firing order 1-5-3-6-2-4



A=1

B=5

C=3

A=6

B=2

C=4



Of course you can start anywhere in the firing order ,but if you haven't done this much ,its easiest to start at A and follow thru.



( this engine probably has TopStop injectors and there is also another method that csevers refered to but what I have described to you is the easiest and prefered method, at least at our shop)



Hope this isn't too confusing, good luck, let me know if I can be of any other help. -- A Johnson

 

[Crash_AF]

Thanks for the info, that was clearer than what we got before.



Another quick question. When you are on 'A', does it matter if you start with 1 or 6? In other words, does it have to be on 'A' and you check to see which (1 or 6) is on the compression stroke or does that matter? Also, if you do need to determine this, what's the best procedure?



Also, what's the tolerance for the mark in relation to the cast pointer? (IE, how far off the pointer can you be?)



Thanks again,

Joe

 

[A Johnson]

It does not matter where you start, the injector will be bottomed in the cup(rocker lever all the way down when you are on the compression stroke. You need to start with the one that is on the compression stroke.



If the mark is 1/2 inch or so before the pointer or closer you are ok, I would not set it after the mark has turned past the pointer, either back it up or roll it onto the next set mark and start again.



A Johnson

 

[Crash_AF]

It's alive!!!

It's alive!!!



Thanks for the help, my airman and I went over to the pumphouse at 0730 and had the engine running by 0900 so the boss is happy which means we're happy.



Thanks again for your help. Oo. I just love the TDR!!!



Later,

Joe

 

[A Johnson]

Congratulations, I'm honored to be a help to you. Can you describe to me what you found? Did the acc drive appear to be in time. Was the overhead setting messed up?



I would just kinda like to know if you have the time.

A Johnson

 

[Crash_AF]

The accessory drive was in time and from what I was able to find out from talking with the crew that worked on it, they were following the dial indicator pattern for adjusting the valves and using the torque settings so the valve timing was FUBAR. (In other words, he only listened to half of what the Cummins rep told him. ) Once my airman and I set the injector torque and valve clearances by what you sent me, it fired right off.



Thanks again for your help.



Later,

Joe