Just overhauled the engine in my D4C, did nothing to the injection pump, motor was running good before overhaul,just sat it aside and reinstalled. The engine wouldn't start seemed not to be getting fuel to the injectors, so I removed the individual injection pumps thinking one was stuck, got the engine running but #4 is dead. Bleeding all the lines #1-3, with the engine running, I have a full flow of fulel, no air bubbles, but when I break #4 there is quite a bit of fuel coming out but there is also a constant supply of air that will not clear up. Has anyone had this problem? The service manual says not to swap the individual pumps from hole to hole but I can't see what that would hurt.The only other solution I can see is replacing the individual pump with a new one,but I hate to just throw money at it. I would appreciate any help. Thanks.
Try swapping two injectors see if you have a bad one.... Am I wrong, or do I remember that those unit pumps are supposed to be individually shimmed? You may have stuck one now if it got stroked too far.
I may be way off base but are you sure the air is coming from the pump and not from the injector? Just wondering if the air you are seeing is compression air being pushed back through the injector nozzle. Don't even know if this is possible. I would try swaping a couple as lantraxco says to see if the problem follows the injector. At least that will only cost you some time and not parts. Where's Pumpguy when you need him ;-)
Thanks, lantraxco but this engine has the newer scroll type injection pump, it can not be shimmed, and yes kshansen, it is possible to get compression back thru a bad injector,though I have not had that happen before, but I have heard of it.I have had the injector line completely off #4 with the engine running to test for that, it seems to be spraying fuel and air also,it would be kind of hard to tell though, I didn't notice any visible sign of compression coming back thru the injector line. Perhaps I could make an adaptor to attach a guage to the line and make sure but I don't think thats the problem I am pretty sure that injector is a new one I put in a while back. Swapping the injectors isn't that much of chore though. I don't know who Pumpguy is but I wish he were here also.
I have seen compression come back through a injector, cat 3306 in a 973 if memory holds true. Checking for a miss, cracked line and it blew back quite oddly.
D4C doesn't mean squat. Need a s/n or at least identify if it's a PC or DI engine. If it's a PC engine it is possible to have compression leak back into the fuel injection pump due to a faulty capsule, capsule not seating in the bore or capsule distorted from over tightening the retaining nut. Injection pump check valves are meant to check hydraulic flow and are not necessarily bubble tight shutoffs. Check upstream capsules as the compression air tends to travel to the last pump on the fuel gallery (#4) in this case. Bore seat can be cleaned up/checked by making a tool out of a capsule and holder along with a little valve grinding compound. Can also be checked with Prussian Blue indicator.
Forgot to mention a trick learned from tctractors on checking for leaks. Disconnect the injector line at the injectors one at a time. Squirt some lube oil into the injector fitting, run the engine and observe if the oil gets blown out of the fitting.
O.M. its not everyone that will strip out fuel elements fron the scroll pump with special tool needed but cannot find a duff fuel capsule, I had a duff capsule on a D6C (333C Engine) on monday I knew what it was via the phone call asking for help, so a 3 hour drive 144 miles and 10 mins to fix, usualy the gauze filter in the capsule has a hole in it as a tell tail, if the lines are undone 1 at a time the line with all the froth is the knacker injector, to bleed the system if the fuel hand primer is a bit u/s just leave the injector lines undone some with the speed control in the stop position, this works well with a good bit of vimto (Diesel or Kero) in the tank, as dont forget this engine will run on central heating oil just as well as Diesel, CAT say so. tctractors