Engine/Transmission (1998.5 - 2002) Comments on Cummins Overrev?

[Doc Tinker]

Found this on another site. Anybody care to make any comments?





http://www.anyboard.net/autos/trucks/DodgeCumminsRam/posts/29.shtml



Doc

 

[CumminsAholic]

1100 rpm over rev... . that's 30% more than it should rev. I dunno how you could get the rpm up to 4500. Well, maybe Piers, HVAC, or Adam (even thought he's a dozen valver) could get that high; Corey

 

[Amianthus]

If he truly wants to know what went wrong and how, take it to a Cummins shop. The diagnostic procedure is excellent and they would be able to tell them everything they never wanted to know about that engine failure. But it costs money to have the right answers.

 

[Todd T]

his "client" it sounds like, either missed a gear or took a huge hill, out of control. the only thing that would cause the valves to float is RPM's if it ran out of oil they would go soft. he must have put it in third instead of fifth, out on the highway with enough of a load that the rear tires couldnt skid.



chaulk that one up under "lessons learned".

 

[Doc Tinker]

Missing a gear, if you mean not getting it into gear, wouldn't cause that. The engine has a governor and you can floor the engine without overrevving, unless the governor is bad.



Now, if you mean dropping into too low of a gear, when downshifting, then yes, it could cause an overrev situation. But, would that cause the valves to hit the pistons, which is what I think happened?



As far as the low oil or low oil pressure... The Cummins uses solid lifters, I believe, and they will not mush out, which is what I call "float". If there was a low oil pressure situation the valves could hang in the guides and cause contact with the pistons. There would be other signs of low oil pressure damage it that happened.



Just my thoughts,



Doc





PS - I just thought of another situation that can cause this problem - Runaway, which can be caused by the intake system pulling in vapors or oil.

 

[Jff24Gordn]

Doc, you rev it up high enough and the valve cant get out of the way of the piston, and boom. And needless to say, it aint desinged to be able to stand the valve hitting the piston. Stuff bends, valves or rods.

 

[Doc Tinker]

I'll agree to your point, Wayne, but 1100 rpm over is about 4300 rpm - surely the valve springs are heavier than what Mrs Doc's Mazda has and that car redlines at 6500. I think it would take more than 1100 over to do it. Of course the Maszda would have hydraulic lifters and would float out before it hits 6500.



I think over-revving the Cummins to that point will cause other damage, like lower-end and wrist pins, rather than valve slap.



Another thought is backpressure - They sell heavy duty exhaust valve springs for the 12v to use with an exhaust brake, presumably to prevent valve slap. Is it possible that an exhaust brake or blocked catalytic converter could cause the problem?



Just thinking out loud - Jump in and give me an opinion guys!



Doc

 

[Todd G]

They don't say what year the truck is. IF it was a 12 valve, and it had an exhaust brake with the original valve springs, then there could be a problem.

 

[B.G. Smith]

Valve float

Doc, I would think if this is a true story that the reason for float at that rpm is the weight of the valve train components. Still seems awful low. Had to put into lower gear coming dawn a good grade. bg

 

[Doc Tinker]

What do you guys make of the theory that the clutch would blow before the valve train?



Doc

 

[B.G. Smith]

Over=rev

If the clutch will take the load going up there is no way it would give out just turning the engine. Now if you really over-rev, say above 9k, then you would probably have a two piece truck. bg

 

[Pete Peterson]

Go to the BD web site and look at the movie of Piers doing the smoke show. One has the camera inside the truck , now tell me what you see on the tach!!!!! Hmmmm... ... ... ... ... . Pete

 

[Jff24Gordn]

Before you want to take a 12v up to high rpms, you first install heavier valve springs. then it will spin that fast without a problem.

 

[Doc Tinker]

More insite on the "over-revved" Cummins

OK guys, I now have some more insite on the "over-revved" Cummins.



Here is some information that sheds some light on why the truck owner decided to get legal help, rather than eating the cost of fixing his engine.



This came to me from Justin, the truck owner's lawyer - I know what most of you probably think of lawyers but Justin is seriously trying to help out one of our peers who appears to have gotten the short end and your comments might help him out.



"The stems on the valves were bent and a few of the rocker arms were broken.



My client admits to trying to pull start it to no avail. He was on a sandy road.



He has been driving diesel pickups, tractors and semi-tractor trailer rigs for 25 yrs. He is certain that he did not cause this problem. Which makes sense, or he wouldn't have had to try to pull it to start it. The downhill w/a load scenario is out as this never happened.



3 months prior to the current problem, a piston broke and slammed against the head. My client was living in Colorado. He bought the pickup in Oklahoma. The Colorado mechanic he took it to took 45 days to replace the head. We and the selling dealer both asked that the engine be replaced, or at least the head and block, but Chysler would not authorize that. My guess is the current problems all stem from this first incident.



It appears that the first mehanic was not familiar with diesel engines as they claimed they needed a special tool to take the head off. The special tool, according to the selling dealer, was a metric socket. Then they said the(y) couldn't get a head for weeks. The selling dealer had one in their shop the next day.



One shade tree mechanic has told me that it is possible that there were more problems than just the head. But the pickup never had much power after the Colorado mechanic got through with it.



My client and the mechanic had a 'falling out' and refused to do any more work on the pickup. So my client limped it to Oklahoma at about 35-40 mph. When he got here it wouldn't start, he pulled it, then loaded it on a trailer and took it to a dealer in Oklahoma. It is now in Kansas City as Chrysler Financial repossessed it. I have not seen the engine or parts, but were emailed some pictures at one time.



I don't know what else I can tell you. I need an expert who will either travel to KC to see it, or who is in the KC area so they can look at it and go from there. Any suggestions?



One problem D-C has is there was a safety recall on this '98 Dodge Ram 3500. Its the 5. 9L. The recall notice says 'Reprogram ECM for engine speed increase. ' Apparently there was a problem with the ECM which would cause the engine speed to increase and cause accidents. No witness of D-C's can tell me how we (they) know this ECM problem did not cause the overrev. "









There you have it. Any expert witnesses out there?



Doc

 

[Doc Tinker]

I suppose it is possible to bend valves in the 5. 9 Cummins, when over revving the engine, but I personally believe that it is highly unlikely. My reasoning for that is the fact that the valves are at right angles to the crown of the piston, unlike other head designs which have the valves at a slight angle. Wouldn't the valves simply pop back to the seat if the flat crown of the head happened to make contact?



The only time I've seen bent valves in engines with this head design, is when a timing belt or chain goes bad.



Now, let's look at the other facts in this case.



We now know that the engine had problems before the complete destruction of the valve train. It's supposed that the Colorado mechanic was inexperienced at servicing the 5. 9 Cummins. I presume that he was an employee of a D-C dealer and is an experienced gas engine mechanic. I don't know if Chrysler has any engines that require valve lash adjustments, so I assume that the mechanic is inexperienced with the proceedure.



If the valve train was improperly adjusted, as would be indicated by low power problem that the client experienced when he drove the truck back to Oklahoma... can you guys see where I am taking you with this?



Another problem that seems to loom, is the computer recording of a 1100 rpm overspeed. How do we know that the overspeed happened at the hands of the client? Is it possible that the Colorado mechanic caused the overspeed while working on the engine, by overriding the governor? Did the mechanic scan the ECM and clear the codes when he completed the job?



Here is a link to a TSB at Fritz's site, I believe this supports my theory of how the valves probably can't be damaged by an over-rev situation. Cummins apparently isn't too concerned about damage, beyond the bent push tubes, as described in this TSB

http://www.dodgeram.org/tech/tsb/2000/cummins01-06-00.htm



Here is the Recall information, at Fritz's site, for the Engine Speed Increase, as mentioned in Justins statement.

http://www.dodgeram.org/tech/tsb/recalls/recall_799.htm



Doc

 

[Marco]

There is NO way to overrev the engine.



The ECM has a "limiter" that shuts the engine down at 3500 RPM.

When that limiter is hit, the engine shuts down. You need to restart the engine then...

I don't see any way to get over that RPM limit without a BIG load and downshifting.



Marco

 

[B.G. Smith]

Overspeed

With that said, the only other way that the pistons could get into the valves would be a valve timing problem, which Doc is suggesting. Maybe the 1100 rpm overrev is a smoke screen from the DC people. I wonder if they have looked at the timing gears? bg

 

[Doc Tinker]

Plot thickens

OK - I have some photos and more information to share.



First I'll share the new information and then I'll post the photos below. It appears that I can't post two photos in the same post, using the forums photo attachment utility and I'm having trouble uploading to my ISP server.





"On the computer readings, the mechanic in Oklahoma who discovered the valve problem testified that he tried to start the vehicle about 6 times. Then hooked up the chip reader and the reading showed the overrev occurred 1 start earlier.



Now assuming the chip actually reads 'starts' and not hits on the starter, this seems implausible because the engine would not start with this damage. It is obvious that this engine has not started since the valve problem. If the chip reads # of times the starter was hit since the event occurred, it appears that the mechanic did it while on the lot prior to hooking up the machine.



It is my understanding that on one vehicle with valve problem like this, the fuel injector pump was out of time. Somehow that caused the valves to float. Unfortuneately, I am exceeding my knowledge of these engines. How would an out of time fuel pump result in floated valves?"

 

[Doc Tinker]

Photo 1

Photo 1

 

[Doc Tinker]

Photo 2

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