Engine/Transmission (1994 - 1998) Something's knocking.....

[BigPapa]

Well, from some previous threads I figured I had a "fuel knock". I have a '95 that came stock as an auto that I converted to a 5-speed. It has 200K miles. It has been well cared for, oil changed every 5K miles, Rotella, Fleetguard, never pulled anything heavy or been run very hard. It was stock except for exhaust and a BHAF until I installed a used set of 215's that I had cleaned and tested trying to get rid of the "fuel knock". It is most noticable at around 1500-1800 RPM on level ground with light throttle, just enough to hold speed. It's worse before the coolant temps come up. Seems to go away under heavy throttle and deceleration. Sounds like a rod to me. Here's what I've done so far:

1. Changed fuel filter.
   
2. Adjusted valves, none were seriously out.
   
3. Cut the last oil filter apart and spread the element out, no visible metal even with a magnifying glass.
   
4. Installed a new overflow valve, spring was VERY short.
   
5. Installed new transfer pump, did get rid of a nagging "tapping" sound.
   
6. Removed the fuel heater, leaking fuel at electrical connector.
   

Only thing left fuel wise is benching the pump and timing. I really don't want to do the timing first since that will be done when the pump is removed, but I don't want to spend (read "Don't have") the $400-500 to bench the pump if it's not necessary.



Am I chasing the proverbial goose? If it is a rod, can I change rod bearings by pulling the oil pan without pulling the motor? Should I attempt a rebuild or go with a reman short block?



Thanks,

Scott

 

[ABorchard]

I think what you have is fuel related. Since you've already tested the injectors my feeling is it's pump rebuild time.

Just what you wanted to hear I'm sure.

 

[Tardog]

It sounds like what others including myself call a tick, it is mainly heard on the drivers side mostly when cold. Maybe this isn't the problem but it could be, hopefully it is then it not a problem. The noise seems to come from the fuel lines/ pump pressure as it surges back to the tank. There is more talk about it here in the forms. Good luck.

 

[BigPapa]

Tardog,



I'm familiar with what your referring to and I don't think that's it. I'm afraid it is the IP or a rod. Neither are good for me.



Scott

 

[Tardog]

Rod maybe but the other possibility is a piston skirt. Had one break in a GMC and it caused the piston to slap but noise got less as it heated up as tolerances got tighter. Would a stelascope help you narrow down the location?

 

[RDupree]

dude,if you think its a rod take your oil filter off and cut it in half,pull the paper pleats out and see if there is metal,brass,steel,aluim in the filter. if its clean,its not a rod. simple.

 

[OTRPU]

RD, I think I read in his original post that he has already done this. I don't know what it is, my 99 knocks lots. Sometimes under load just cruisin down the Interstate, other times just sittin in the drive and takin it up to 2,000. I know it's a diesel, but this is sort of a hollow tiney knock. Don't know what it is. . . but it's scary. Hope you find it and it don't cost much.



Cheers,

Steve J

 

[Missouri Mule]

Try running diesel fuel conditioner/cleaner thru the tank. One of your delivery valves mite be sticking.

Of course this depends how loud the knock is?

 

[BigPapa]

Forgot, did that after the fuel filter change.



Scott

 

[budctdca]

BigPApa, It might be advisable to install a magnetic oil drain plug the next time you change your oil, this along with with dissecting your oil filter will help rule out engine problems. Sounds to me like something in the fuel system, I know that the older injection pumps are noisy. some food for thought, as mine is a 97 and is pretty noisy. Hows your MPG's?

 

[BigPapa]

budctdca,



Tell me if I'm wrong but I figure if it gets to where it's shaving off steel instead of brass I think I'd know it before I see it on the drain plug.



As far as milage goes I have averaged 23 MPG over the past 20K miles. Last tank was 25 MPG but that was just one tank. Oo.



Thanks,

Scott

 

[budctdca]

brass is non magnetic, so you wouldnt see that on the drainplug but you would be able to see steel

 

[BigPapa]

I noticed today while running the engine up around 1K RPM's in neutral to help the AC that the engine has a bad "shake" from 1K to 1250 RPM's. Above 1250 it definetly shakes but not as bad. It's like something is really out of balance or it's missing on one cylinder (or more!)



Does the orientation of the balancer mean anything? I had it off 2 weeks ago tabbing the KDP but there was nothing in the instructions about marking the balancer and making sure it goes back the way it was.



Is this "shaking" normal?



Thanks,

Scott

 

[RChesney]

This is interesting. I have a 1998 12V that just started a "ticking" noise that's most noticable on the driver's side. Didn't notice it before I did some work on the fuel system which included removing the fuel return valve and stretching the spring to 1/2". That seemed to help performance, but that's also when the "ticking" started. Sounds just like a loose valve. Noticed most at idle or light load (like window down and going past a guardrail really echoes back).

 

[Missouri Mule]

Seems like something is coming apart.

An oil analysis should be able to tell you if and what it is.

 

[Sandifer]

Rchesney, My '95 makes the same noise. It doesn't seem to effect my performance but it doesn't seem normal. Sounds like a lifter tap. I notice it at idle and freerevving just above idle.

 

[PKemp]

This is a very, very common problem for the 95 thru 97 with the P7100 pump.

It has antagonized and irritated so many people, some even rebuilt their motors only to find the tick/knock still there. Most just give up after awhile when they realize that their motors are not going to come apart. I myself have spent literally thousands of dollars in search of the cause. I believe I've found an answer. It is fuel related and has to do with the p7100 pumps need for a constant fuel pressure. When they are tested they use a 50 gallon tank suspended about 10 feet above the floor to feed the lift pump. Gravity and the weight of the fuel provide a constant pressure on the lift pump, relieving it of the duty to suck fuel from the tank which is a long way away and either at or below the level of the lift pump in an actual truck. The lift pump being cam/rod activated also contributes to the "tick/knock" sound.

What to do??? Well, it is a bit radical but I and many others have installed pusher pumps in the line and taken out the lift pump. I myself have removed the filter assembly, lift pump and fuel heater (warm climate) and replaced it all with a F. A. S. S. fuel system. The p7100 now has a constant fuel pressure under any load condition regardless of the horsepower mods. No knock, no tick, smooth as glass acceleration, immediate response to the pedal, even better fuel mileage. An added plus is that the fuel filter and water separator on the FASS system is easy to get at and change. For more information contact Mark at Piers Diesel Research. He will eliviate your concerns and calm your fears... ... The only drawback is that it will cost around $550. 00... . For me and all the time and money I've already spent hunting this noise, it was well worth it...

Happy "smooth", "quiet" motoring !!!!!

 

[Cumminsman]

scott, if you think that it may be a rod bearing the easiest way that i know to check it is. crack the injector lines one by one to see if the noise goes away when you unload the cylinder. that's how we found a rod bearing down on the #6 of a friends 24v. later, nick

 

[BigPapa]

Figured I'd post an update.



I changed out the stock injectors with a set of tested and cleaned 215's. No change in the knock.



I have yet to do an oil sample but I have taken my truck to 4 people that have lots of experience with the Cummins B. All 4 have told me that knowing how the truck has been maintained they would wager that I do not have internal engine problems. The consensus is that I have some "slight" wear on the injector pump causing an "irregular exhaust". I read that as one cylinder is getting more or less fuel than the others causing a "knock". The Bosch dealer said that my rack may be sticking just enough to cause it or I may have a delivery valve sticking just enough to cause it.



Either way I go, everyone said to drive on and if it gets worse let them know. I will get an oil sample this weekend and I'm planning to advance my timing and install a cam plate and 3K GSK as soon as I can afford it. Anymore developments and I'll post.



Scott

 

[CumminsPower98]

RChesney, your ticking sound is coming from your lift pump. Stretching the spring in the overflow valve raised the fuel pressure. The lift pump pumps fuel on the return stroke via spring pressure so if this pump spring becomes weak or the fuel pressure is too high it will cause the pump piston to return too slowly alowing slack to ocure between the pump push rod and the cam lobe.



Mark

This is interesting. I have a 1998 12V that just started a "ticking" noise that's most noticable on the driver's side. Didn't notice it before I did some work on the fuel system which included removing the fuel return valve and stretching the spring to 1/2". That seemed to help performance, but that's also when the "ticking" started. Sounds just like a loose valve. Noticed most at idle or light load (like window down and going past a guardrail really echoes back).