Engine/Transmission (1994 - 1998) Something not good has happened to my cummins!

[PGWIN]

First i've prepared myself for the worst - just king of expecting it.

So heres the story,

1. (thump / pulsing engine_ about 2k miles ago i kept hearing a "thump sound (kind of like a piston with more fire than the others is what i would descibe it as I think i first sarted hearing this about 2k miles back and maybe it got progressively louder (not a deep nock or a tick). On our last fiver trip - we picked up my son and continuteed to drive. Within 5 miles of picking him up and driving on the freeway with the trailer he asks what's that knock in your engine. He hadn't driven with us - we picked him up and he notices it right away. Usually i notice it more heavily loaded below 2000 rpm and really max thump tone is around 15-1600 rpm under heavy load.

2. Black smoke: Yesterday i was pulling a 6K lb trailer and it was annoying listening to this "thump for 300 miles. When i put the exhaust brake on (valve post turbo) i got a good cloud of black unburned fuel in the exhust = very noticiable (i noticed this both times - and so did the driver behind me - pretty good hazy vision in the mirror). What would cause this?. Only thing i can think of is their is a feedback of exhaust gas that somehow is causing the pump to increase fueling or otherwise burn unburned fuel that has accumulated.

3. When pulling a heavy trailer i really notice the pulsating power in 1st gear - under heavy accelleration with 15k trailer in 1st - its very apparent - unloaded i wouldnt notice it.

Any thoughs on the sobject -im not sure the black exhaust brake is related to "the thump (sounds and feels like a piston getting a biggers squirt of fuel - but that can be deceptive) All this said i got 20+ MPG on the last tank which was 250 miles freeway 150 miles pokie 35mph stop and go streets.

Where to start - something is definately wrong. Compresssion , visual valve check of clearances.

I'm prepared for the wost valves, hole in piston, bent valve, valve push rods, etc.

Thx

Paul

 

[RWherley]

Check your injectors ASAP you could have nozzle damage on one, if that is the case bore scope that cylinder extra fuel or a bad spray pattern can wash down the cylinder and cause damage to the rings and wall. and check valve lash just to safe

 

[NIsaacs]

I would guess you may have an exhaust valve not opening for what ever reason. Flat cam or lifter, bent pushrod or broken rocker. The "thump" might be when the exhaust exits the intake when the intake opens.

Nick

 

[PGWIN]

I would guess you may have an exhaust valve not opening for what ever reason. Flat cam or lifter, bent pushrod or broken rocker. The "thump" might be when the exhaust exits the intake when the intake opens.

Nick

My suspicions are alligned with this. There was a time a while back when my exhaust brake popped on at higher than anticipated rpms (long story there) and i always wondered if i hit valve float. Alledgedly there the pressure on the valve is set to prevent this by design but i didn't set it up, so i don't know if that fail safe is present.

I think i'll start with valve clearances and report back. Will likely take me a week or so before i get to it.

 

[PGWIN]

Ok valve Clearance Results:

Cylinder / Int / Exh

#1 / .008 / .018
#2 / .008 / .017
#3 / .009 / .018
#4 / .0115 / .019
#5 / .011 / .018
#6 / .008 / .0185

Valves: So does this point strongly that valves are ok, i would think it means no bent pushrods? If i remember right I set the valves at 0.009/0.018 and the last time i actually adjusted them was at about 75K miles, checked them around 90K miles - and didn't bother adusting as they were within +- 0.001. Currenlty i'm at 105K miles.

Where next:? Would it make sense to crack the injector lines one at a time when running to see if one cylinder does not drop out? or pull the injectors and get them pop checked? Or?

Lastly - is there any chance the pump govenor spring settings could cause this. I'm 3 clicks backed off to get higher top fueling - stock spring set. Certainly this wansn't present after changing the spring setting. That change was about 8K miles ago.

Thoughts on next logical steps?

thx,

Paul

 

[PGWIN]

Adjusted valves all back to .009 and .018/.019 on exhaust.

Then checked all cylinders by cracking injector lines, all dropped sharply and grossly apparent.

So think this is a good sign.

I did a test drive, perhaps my imagination but appeared not so apparent of the "thump" - are valve adjustments "placebo's"?

Heres a few videos for sound demonstration.

I'm out of next logical steps.

Pop test injectors? Any good places in Sacramento?

Last pull of 15k Trailer up not too big a grade - can clearly hear the thump:https://youtu.be/zJhy56HRs6g


Idle after valve adjustment, lopi idle same as before, thump not quite a present on max acceleration - jury out when towing, still not what I am looking for in smoothness.
https://youtu.be/r-Rq5AVzbeE
https://youtu.be/GnAGz91pH3M

 

[BigPapa]

Loosening the governor springs will DROP your top end fueling. If you want more top end fueling I'd suggest a good GSK, preferrably NOT the Pacbrake kit. I have heard of a lot of idle issues from them.

 

[GAmes]

Ok valve Clearance Results:

Cylinder / Int / Exh

#1 / .008 / .018
#2 / .008 / .017
#3 / .009 / .018
#4 / .0115 / .019
#5 / .011 / .018
#6 / .008 / .0185

Valves: So does this point strongly that valves are ok, i would think it means no bent pushrods?

Lastly - is there any chance the pump govenor spring settings could cause this. I'm 3 clicks backed off to get higher top fueling - stock spring set.

Checking the valve lash doesn't tell you if a a cam lobe is flat. There is no pressure on the rocker while checking the gap. Measuring the lift of each pushrod while rotating the engine is the method to check the cam. Rotating the pushrods with your fingers when there isn't any pressure on them could Possibly show a bent pushrod.

Gov spring tension can do funny things to the idle. BigPapa is correct. Loosening the springs will decrease your top end fueling. Are you sure you didn't tighten them? Either way, it wouldn't cost you anything to reverse what you did, if for no other reason than to rule them out.

 

[NIsaacs]

I would pull your fan belt and see if the sound is gone or still there. The belt tensioner can make some weird sounds when they start to fail.

Nick

 

[PGWIN]

Update

On GAmes advice:

Checked all valve pushrods - when relaxed all turn by hand very easy - no variable resistance at all.

Checked lift of each valve with dial indicator - granted this wasn't an ideal mag base inditcator and matching angle of valve is "close" not perfect which will make an difference in measurement



Cyl #: Exh / Intake

1: .416 / .390
2: .415 / .385
3: .415 / .390
4: .416 / .375
5: .416 / .385
6: .415 / .380

So maybe there is some delta in the intake valves, some is metrology error, I wouldn't susspect that much would account for the thump.


Checked Gov springs, and yes i did state it backwards above, original was 3 clicks tightened. I backed them off 2 clicks to 0.062" down from spring stud top (dial caliper method). Clearly a noticeable difference in engine smoothness. The truck is much "happier" in this condition, lopi idle gone, and overall just sounds happier through the RPM range. Beyond the lopi idle gone - it is a more pleasing sound.

Though the the thump is still there if you listen closely. Video uploading - will take 30 more minutes : https://youtu.be/eWft5oqxcoI

Didn't get to fuel pressure yet.

 

[GAmes]

I noticed the engine was cold, is it the same at operating temp? Also, still have the cat converter? Stock muffler?

 

[PGWIN]

Yes - the signiture is the same at first start-up stone cold or at maximum temperature.


Cat converter and muffler are stock, and i dont think ever tampered with.

 

[GAmes]

Cat converters do clog up, but I don't know the symptoms when they do. Previous owner could have been into non-diesel fuels (waste motor oil, etc). You could investigate that avenue.

 

[PGWIN]

Pop test results:

But first - fuel pressure is 24 at idle speed and drops to about 22 at 2000 rpm unlaoded.
Under load i it is about 18psi.

Pop test: i went to Valley Fuel Injection and Turbo in Woodland, CA (Valley Fuel Injection & Turbo, Inc. - Home) - who is the local authorized Bosch dealer in the area. They generously pop test them as courtesy and the best part invited me to watch (fantastic!). I was thouroughly impressed, completely knoledgeable and more than willing to discuss and pragmatically help
258, 252, 260, 260, 270, and then #1 injector popped at ~ 220 Bar. So they shimmed this injector to get it back to 260 Bar.

Seems this is a good hope but won't know how this impacts it until tomorrow after i get it buttoned back up. Put the injectors in, fuel bleed manifold, ran out of light - so will complete in the AM.

If this doesn't solve the issue - maybe the next is to evaluate the P7100, I believe what Valley fuel does is bench test under pressure load for flow balance and at max operating temperature of the pump. I'm not sure if there are minor adjustements they can make to the pump to balance it. They said this should have the ........-860 pump, and if it has copper washers in the delivery valves they should be changed out with steel washers - relates to this pump that can have an operating issue at max temp - which i expererienced when water temp got to 215F after a major grade.

Tried to see in the cylindars with my endoscope - not a chance so had to abort that for now.
Anyway - will see tomorrow.

 

[PGWIN]

Well - no cigar today. The shimmed injector to 260Bar from 220 really didn't make much difference.

Video below shows going up the biggest mole hill around here - trying to push on the pedel w/o gaining to much speed. Really no threat of that.

https://www.youtube.com/edit?o=U&video_id=nYAu-sbtDQQ

And the sound after super cooling the P7100 with the water hose for several minutes.

https://www.youtube.com/watch?v=855fToxKNJY

Anyone have a new theory? I may need to think on this for a few days - where to go next.

Pump? If so what is the best way to approach that? Any other ways to diagnose a pump other than taking to the Bosch shop?

 

[NIsaacs]

I would pull your fan belt and see if the sound is gone or still there. The belt tensioner can make some weird sounds when they start to fail.

Nick

Did you do this yet?

Nick

 

[surfbeetle]

Based on your comment that it's putting out unburnt fuel and that your valves seem to be okay, I was wondering if there's an issue with the wastegate or the hose that connects the AFC to the turbo/wastegate that's causing some sort of fueling fluctuation with the injection pump. Assuming that the engine itself is okay, then I think process of elimination with the accessories is the next step. So as was previously stated, try taking the serpentine belt off and see if the noise continues. Don't run it for too long as the water pump is disconnected when you don't have the belt on. The tensioner does go bad, I had to replace mine finally a couple of years ago.

 

[PGWIN]

Based on your comment that it's putting out unburnt fuel and that your valves seem to be okay, I was wondering if there's an issue with the wastegate or the hose that connects the AFC to the turbo/wastegate that's causing some sort of fueling fluctuation with the injection pump. Assuming that the engine itself is okay, then I think process of elimination with the accessories is the next step. So as was previously stated, try taking the serpentine belt off and see if the noise continues. Don't run it for too long as the water pump is disconnected when you don't have the belt on. The tensioner does go bad, I had to replace mine finally a couple of years ago.

I'll do the serpentine belt and startup. The good part is the signituer is there wheather it is cold or hot, and it likely will take at least 5 minutes to even begin to get warm - though will watch he temp - really only need about 3 minutes.

I do like that idea to eliminate the pesky fan noise as well that masks all things.

The other part i think about is the harmonic balancer, i'm not sure how much this can contribute to noise but i do know it adds to vibration significantly if the rubber fails and it spins. I would be more incliced to think this could be a source of noise compared to idler, but we shall see.

WRT the unburned fuel, i've driven about 40 miles in recent days after wrenching and can't get it to haze with the exhaust brake on again, and i've tried. So going to call this an unexplained event at this point rather than a trend.

However currently the pressure feed from pump AFC to waste gate is blocked off to see what i could get for max boost, 18psi is absolute tops - which i suppose is all the fuel it can get. i wasn't too worried about not having an elbo as i can't get too much boost. Any issue with this other than elimination of a protection mechnanism? This is a 95 and didn't have teh 215 pump/fueling to get to 23psi stock.

Video coming tomorrow.

 

[PGWIN]

Ok - heres the SERPENTINE BELT DELETE: https://www.youtube.com/edit?o=U&video_id=81-HswI_R1A

Well i did check out the FSS and as you can see the boot was a little bit deteriorated. Cleaned it all up - still shiny no real wear, applied 60 % moly grease to it - will get a new boot.



I did adjust this and found it was limiting the rack travel or about 1/4" rod motion was still needed to have the pump arem all the way against its stop. The FSS mounting bolts have never been turned - but someone may have adjusted it in the past at the arm end? I do know the PO took it to the Dodge dealer very early on due to "white smoke" and i suspect those dealer techs (some of them!) may not not what they twiddling!

Adjusted this like Cowboy-303 (thx), and it now produces 24psi boost max, prior to this could not ever get past 18. It doesn't get from 18 to 24psi super fast - maybe takes 4-5 seconds - would need to watch it again.

THUMP -pulse still there. Guess i'll look at fuel pressure next - maybe change the lift pump (current is a Cummins, purchased from Geno's, made in China, with 4k miles on it). The fuel pressure operated this way right out of the box, so if the pumpe is the culprit it was this way from new.

I would suspect this new lift pump is not moving the volume of fuel per each piston stroke as it should - which would explain the drop in pressure when the pump drinks more. When i first installed this pump - i thought it ticked whereas my previouse one didn't - i distinctly remember thinking that right after install. Whew - this is a long road!

 

[BigPapa]

Cleaned it all up - still shiny no real wear, applied 60 % moly grease to it - will get a new boot.!

Clean all the grease off, it needs to be dry. The grease won't do anything but gum it up. The boot is not necessary, either. Mine has been running dry and without a boot for over 300K miles. It's the original FSS that came on the engine in '95.