Gday all. Just wondering if any of you have come across a Cummins NH220 running on after shutdown (can be up to 30 seconds). Was fine before full engine over haul. Has a recon PT pump and new injectors. The overhead adjustments have been checked several times and all good, new filters and fuel, fuel float tank disassembled cleaned and inspected. On shut down with fuel return removed theres a large amount of spluttering fuel vapour not a solid stream of fuel as there should be. Obviously somethings been over looked.
Pull the injectors, inspect the cups and the O-rings sounds like may be getting some compression back into the fuel passages basically pushing fuel out and into delivery. PT stands for Pressure Time, when shut a Cummins down you remove the 'Pressure' by closing a solenoid(trucks) or pulling a shut down lever closing the port. Can also be a restriction or absolute blockage in the return line from the heads/injectors look there as well all the way back to tank. Is a separate overpressure return from the pump that tees into that same return line. If this is the external line Komatsu derivative engine that has a feed and return to each injector you MAY have a bad injector allowing pressure back up thru the device and into the fuel channels. Is it hard to start after the run on?
Thanks mate. My next move was to pull injectors so that confirms my thoughts as it is exactly as though compression is entering the fuel rails. Have checked all the fuel return and supply lines for blockages and all spot on. Ive also removed the fuel return tubes from each injector open to atmosphere blocking the rail to inspect the gasses coming out, all of which seemed equal. It is as though gas is entering the delivery side for this to be so. I then capped off the supply to each injector one at a time, starting the engine to see if a difference was noticed which nothing substantial was. Engine starts fine and has good power, slightly darker smoker than I like but is non turbo. The vent on the komatsus fuel float tank has heavy gasses exiting while running and also pushes quite a bit of fuel out on startup
Does sound to be compression backing into injector regions. The extra pressure of compression on restart in the fuel rail is probably aiding starts.
One other option comes to mind. Is this a 'true' NH Cummins and not a Komatsu clone? Are the injectors unit style(no external lines, fuel galleries in heads)? Did you get 'Top Stop' injectors as replacements for the old unit style? Got to ask as this can lead to this problem. Unit injectors if adjusted on an overhead as was done to the old travel set injectors(.170 travel) they will possibly NOT hit bottom and shut off the compression yet will still inject and run. Cummins injectors ride fully closed, rock open then closed to inject on a reverse cam lobe. If 'Top Stop' style the spring in the injector is captured by a internal nut to the injector body.
Cheers for your reply again mate. This does not have unit style injectors and does have external fuel lines, how ever the top end set is done in a similar manner using the inch pound method. One drama that was noted is that there are no 'vs' marks on the accessory drive pulley anywhere. There are scribed marks but not a 'VS 1-6' etc. I had to setup dial indicators on the injector plunger and valves, carefully watching there functions to get the correct reference mark to start the set off.
Was afraid of that. What I used to do is when the #1 injector started coming up for injection stroke, looked to the acc dr pulley to note what mark coming up. Simple calc 153624 firing order running mates 153/624 1/6 2/5 3/4. I would have to dig out the old manuals I have packed away but the stagger is odd for Cummins for the start of an overhead if you start at I thought letter B. Later model engines used A B C as to timing marks on the pulley.
My 220 manual is on the desk at the shop if you need the info, I had it out the other day helping somebody with torque specs. I can look up the procedure for running OH, snap pics and post if you'd like. It'll be tomorrow am sometime.
Thanks fellas. And i made a balls up in the description by the looks as its a NH220 not 200. That would be muchly appreciated. We did follow the genuine KOMATSU manual which states it should have had 'vs' marks but any of the pulleys or housing may have been changed through out its time.
When you get there we used to start on B or 2-5 on the acc dr indicator which depending on cylinder up was valves on 1 or 6 dependent on which were both loose and injector opposite cylinder for the valves. That is a twenty year unused brain cell firing too so look to the manual.
That brain cell fired again!! Get B or 2-5 up. should have valves on 1 or 6 full open, do the injector next in firing order. 1 would be 5, 6 would 2 then move to next mark next in firing order.
Look on the outside face of the acces. pulley next to the lines,on the inside pulley grove on the pointer side,vs marks should be there. start on any vs mark, set injector then valves on the hole that the valves are closed on then rotate motor to next vs mark. Good luck Bob
This was the old cheat sheet info I used to use: You want to start with A or 1-6 VS. Adjust Inj 3 and valves on 5 Adv to B or 2-5. Adj Inj 6 and valves 3 Adv to C or 3-4. Adj Inj 2 and valves 6 Adv to A or 1-6. Adj Inj 4 and valves 2 Adv to B or 2-5. Adj Inj 1 and valves 4 Adv to C or 3-4. Adj Inj 5 and valves 1 In the 'Olden' days we started at B to only have to reset the injector stroke dial indicator position once otherwise just moved it place to place for each in firing order.
Dmiller in the "real" olden days we used an inch pound torque to set the injectors! Or as one of my working group leaders would do, crank up the engine and adjust them by ear while engine was running at idle!
You probably remember the Supercharged 190's and the six bolt heads I do!! Swinging on a ten foot pipe to get 600# headbolt torque!!
We had one gritty old soul set the rack on 110's running Preferred to adjust the governors by sound! Those were the days.
I am a thinnin' back then That Gritty Old Man Might have been almost 60 years OLD He was just ANCIENT!! Man that has come home to haunt me
Only worked on one or two of those supper charged Cummins. For years there was a rebuilt one of those supercharger sitting in the storage trailer at work. I was always going to take it home just as a conversation piece but it ended up in a scrap trailer during one of the big clean ups at work. And those superchargers were not all aluminum like Detroits!
My old shop foreman at the crane place did that, set them running by ear. Damn good mechanic. Had a fubar'd hand from the 70's. He used to walk around with a rag in his hand. Had a 1693 running with valve cover off......good ole OH cam gears snatched that rag and his hand before he could even think about saying oh ****. Learned a lot from that feller. Still call him from time to time and I haven't worked with him in 16 years. Love the old stuff!
Sorry I missed this part. On top of the fuel shutoff solenoid there is a screw with a screwdriver slot,turn this screw all the way out.should cure your run on. Don't torq set your injectors with that chart miller put up you will have bent push tubes. good luck Bob
True on that! If doing the torque wrench setting when turned to the 1-6VS position and the valves are closed on #1 you would torque set the injector on #1 the adjust both valves on #1. Then turn to the 2-5VS and set the injector on #5 and then valves on #5. Continue through the firing order till all are set. Spec's in my book that is dated 6/65 call for a cold set on injectors of 48 in/lbs and a hot set of 60 in/lbs. Valves are .016 intake and .029 exhaust cold and .014 intake and .027 exhaust. These may be off as I believe the actual settings vary if you have aluminum rocker boxes as opposed to the older cast iron like this book shows. This book even shows a four cylinder version and lists spec's for left hand versions of both four and six cylinder engines! Not to mention the section on rebuilding the super charger!
You guys are correct as to setting with torque wrench with injector on bottom. If these are a top stop style with caged plunger springs taking the lash out on the injector on the chart is correct, those torque to 5 inch pounds just to remove pushrod to injector lash or to set with a dial indicator on the old style.