engine is a 4T390 that cranks and low idles fine but skips/sputters between there and 2000rpm. Runs fine at and above 2000. Black smoke burst visible at cranking and when it is sputtering. Bought used and thought was just a fuel problem. I have drained/cleaned fuel tank, replaced both fuel filters 3 times, checked/cleaned fuel lines, added Sea Foam religiously, had injectors tested (all fine) and tightened everything for air leaks. Also (don't know if related) the hydraulics seem to really bog machine unless it is high rpm. More than any other I have owned. Any ideas/suggestions are appreciated. This thing is testing what little patience I have left.
How many hours? Did you do a compression test when you had the injectors out, and/or does it have excessive blowby? Which injection pump? Does it look clean, or are there any signs somebody has messed with the pump? Kind of sounds like timing, possibly internal to the pump? maybe I'm remembering what TPG said...
You could try timing.. give the pump A LITTLE twist OPPOSITE the direction of the arrow on the name plate. assuming its a CAV, DELPHI pump.
2600 hrs and no compression test done and no to excessive blowby. Pump looks ok except for some rust as previous owner left unit outside a lot. Pump is a Bosch RSV 500. Thanks
On the back of the pump there are two adjusting screws. The smaller one is for the governor spring try tightening it up just a bit. Some of these pumps after awhile the governor spring gets weak and allows the engine to hunt at certain RPMs. There was a new spring for this pump just contact a local pump shop, if you have one, and they should be able to help you out.
Coy.. Its not surging.. its "skipping" is what I gather..?? The bosch pump is a different animal than the CAV/Delphi.. You can still turn it a smidg tho.. The RSV is the Governor type.. 500 is the low idle rpm for the pump.. 1000rpm on the tach in the machine.. IT MAY have a timing pin in/on the inj. pump& engine?? gonna need some pump #'s to be certain.. 10 digit.. Probably something like 9 400 *** ***
Correct # 9 400 030 734. I was told it does have a plastic timing pin that screws out at bottom of pump. Been wondering about the black smoke. Is air my problem, maybe low boost from the turbo?
Not at idle, low or high. There's no significant boost until the engine loads up. The speed is controlled by the amount of fuel, no such thing as too much fuel at idle.
Have you done a valve adjustment? You could also check your valve lift while your in there, I've seen 6bt Cummins intake lobes go flat, run rough/smoke black at lower rpm, then smooth out with boost but be low on power. You say it seems under powered, sounds like three cylinders are doing all the work and one is just along for the ride. You can isolate which cylinder is misfiring by running at the speed which it's missing worst/puffing smoke, loosen each injector line one at a time until the smoking stops, keep your hands/skin away from the high pressure fuel spray!
GOOD diagnostics there Greg.. THATS how ya do it.. & IF your conserned about AIR> just remove the filters BEFORE & during the fuel checks..
I have not done a valve check. I did heat check cylinders and got a moderate difference on #3. I will isolate with fuel as you suggest today and see if I get same results. Thanks for your input.
Okay, cracked each cylinder with motor sputtering. Each cylinder reacted the same so I could not say one was misfiring vs the others. The sputtering seemed to level out with each cracking. The smoke is mainly when you pat the accelerator so it was hard to tell I was doing any good while cracking. Does this make sense?
Not to imply that you do not have a fuel problem but I would make sure the engine mounts are good and not allowing the engine to shake around. have seen this so many times on the earlier series Case hoes.
Wow, okay I will check. Thanks