Hey ya'll... this is my first post, I'm a new member, but far from a new CTD owner. But this one has me stumped...

My Blue Ox is a 92 D350, 418,000 miles on the old girl. The injectors have 250,000 miles on them, the injector pump and lift pump are both original equipment. It gets fuel filters every 10k and PS fuel treatment every tank (it sure loved those oily fuels of years gone by......). Anyhow, that's the background on the truck - here's the problem.

I live up in the mountains of Colorado, and the mtns are where it's the worst. I coast downhill for .5 to 1.5 miles at a stretch heading into the city, and when I get to the bottom and have to accelerate again (or fuel it to maintain speed) it spits, sputters, "backfires" hard a few times - blowing a ton of smoke all the while... then will level out and go. The other day I shot a flame a good 3' out of the stack. (at 5am, it looked pretty cool though :-) ) It does seem to be a bit worse in the cold mornings, but it happens when it's 60 degrees out too.

Other times it acts up:
-If I maintain speed on level ground with a very light throttle, it will "miss" and often throw a whole mess of smoke behind (above) me. Blue/Grey, seems like unburnt fuel (it's not oil, still doesn't burn a drop).
-Hold it for 5+ seconds at a steady rpm above 1500rpm, in any gear, it will begin to sputter and miss.

Most of the time, if I get on the stupid pedal a little harder, it will hiccup a few times hard, then smooth out and accelerate with all it's usual power.

Occasionally it has seemed to miss slightly at idle too, but this is seldom.

I think that's about as best I can describe the problem... hopefully somebody has some thoughts before I just start swapping parts. I know the fueling system in her is long overdue according to standard lifespans of injectors, pumps, etc... but if it ain't broke...........

Thanks in advance!
-BlueOxD350

 

Well...I'm certainly not a super-authority...but I've never heard of a diesel backfiring! Some new spark plugs and a set of points should clear that right up!

Anyway...it certainly sounds like you're dumping a lot of unburned fuel down the pipe as well as "flooding" it. My guess would be really worn out injectors. You're not getting a good spray/vaporization pattern. This lets a lot of unburned fuel out of the cylinder. It starts OK? If runs under power (full load up a hill full boost) OK? Oh, you said it does after it clears the "flood".

Anyone else?

What's the chance that the fuel pin and AFC diaphram are stuck open? That would let lot's of fuel in.

 

Does your injection pump leak at all? How about the overflow? You're definitely getting too much fuel under light load and it sounds like it may be linked to late timing, weather it be because of the pump or a couple lazy injectors. Cheaper to have the injectors pop-tested than it is to have the pump bench tested, so you might want to start there.

 

Hence the "backfiring" in quotes... it was the best way to describe what was going on... especially once I saw the flame show.

I appreciate the input, however... the injection pump doesn't leak at all (unless I run untreated fuel... but the lubricants of my additive keep it sealed right up)... guess I'll pop-test the injectors this week and go from there.

If that ends up being the problem (which, with 250k on 'em, can I be surprised?) is there a better-than-stock variety I should go with to replace 'em? I'm not looking for a smokeshow, or crazy power, etc... stock reliability keeps the cattle and hay movin nicely. Just wondering if I should look aftermarket? Thanks!

 

Sounds like it's time to upgrade.
In reading past threads, it seems like the POD's are a pretty good bang for the buck. If I can handle the smoke (how bad is it? if I'm stack'd and pullin animals, am I gonna smokescreen em? I don't think the critters would appreciate a face full of soot every time I climb a hill...) and for a comparable price to stock replacements, why not get the extra pullin torque.
But does a more aggressive injector place more stress on the injection pump? With 418k on the original one, I fear it's in a delicate state already... should I be concerned that this mod would push it over the edge and into the scrap heap?

 

If your worried about smoke but still want an uprated injector I would suggest the Bosch 190 injector from Piers diesel research(PDR). These are the injectors I am going to get eventually. I'm in colorado also and I think up here at altitude you'll have a hard time keeping the smoke and EGT's under control with the POD's. The bosch 190's are a little less in price than the POD's but you don't get as much power from them so your not getting as much hp per dollar but still a good upgrade and their a brand new injector.

 

I would also agree on the 190's. Without some other mods to the turbo housing etc the POD's get a little too smokey for most.

I would get a tune up done (or do it yourself) and have the timing checked/set with the upgraded injectors. Even after only 150,000 miles on my 93, the timing had worn down to only 1° BTDC, stock is 10°. It was a slobbering beast, but never sputtered or missed. That I would put on the injectors possibly. It is also possible that your lift pump has gone away or your pump is just not reaching peak injection pressure.

If the injection pump wears significantly, the timing will retard due to the longer time for the pump to reach pop-off pressure of the injector. If you pop-test the injectors and they all test out fine, then the pump may be the culprit.

Hope that helps..


Oh and Welcome to DTR!!!!

 

try advancing the timing.

 

I can only relate one such experience as that with a diesel. Bare in mind it was a EMD 645E4 20 cylinder. It wouldn't start and self sustain more than 15 seconds but it shot fire out of the muffler ten feet with a loud boom. Those EMD's are big weed eater engines. They are 2 stroke using a pressureized air box. The turbo is first driven through the timing gears with a sprag clutch. This gives it low power boost. When the fuel is poured in, the turbo overruns the clutch giving it about 20 pounds boost. The malfunction was the turbo drive train. Not enough air to get complete combustion in the engine but enough to cook off in the muffler. In other words you may be suffering incomplete combustion from either a lack of air or a runny injector. Either way good luck and let us know what you find.

 

Thanks for the input, everyone. Now lookin into 190's along with timing check and a valve adjustment. Guess that fills up this weekend. I'll keep ya'll posted on what I find and what the outcome was!

 

ill make this short make a search under blue smoke youll see my name pop up follow my steps i think we had similar problem

1 check for leaks
2 take out injectors have them pop tested "mine had bad copper washers "
3 play with timing on pump
if nothing else works try this last cause theres no going back
tap governor pressure thing check my pics for it before you do that keep me posted oh yea let me guess at 3/4 throttle in park or neutral she misses and gives you blue smoke everyone gona tell you its oil but its unburned fuel at least thats what mine did

hope this helps keep me posted

 

Yeah; sounds to me like either timing, and/or worn out injectors. Keep us posted

Eric

 

190's and upping the timing to 16.5 degrees or so sound like excellent ideas to me. It sounds like it will solve your problem, and the truck will have a little more spunk too. Do you have a pyrometer? If not, it would be a good idea to get one while you're at it.

 

Well I got my 190's from Piers last week, and got them in just before dark last night. And what better time than dusk to turn the downtown stretch into a dragstrip to test her out. The power was there, but...

Unfortunately, this didn't fix my problem. I haven't taken it down the mountain passes yet to really get a feel for it ... but holding the truck at a constant speed, in any gear, above 15-1800 rpm, it sputters along badly.

Looks like next is timing... right? Should I find a Cummins shop specifically, or just a reputable diesel shop to set the timing? (Anybody know of a good one around N. Denver, CO?) Or should I just "bump" the timing myself and see what happens?
Anything else I should be checking out to fix this? I need to head to Michigan in a week, so I REALLY need to get this figured out..........

 

Could you refresh us on your syptoms? If it sputters it almost sounds like a fuel supply problem.