bertram31.com

Not a happy camper today! I just instaaled my injector pump after getting a leak repaired. I bled the system and fired her up. NO problem. I then played with the idle adjustment to get the idle to 650 and then I after about 3 or 4 minutes of running I heard "pop" and she stalled.

I cranked to start back up and it felt like it had less compression. So I pulled a valve cover off and cranked and thats right, NO rocker movement!

Pulled the front cover off and this is what I found......@%*#!!!!!!!

And by the way this engine has LESS THAN 2hours on it! The CAM is brand new OEM from cummins $500 some-odd dollars later!

This broke at the 1st journal, I am hoping this is some kind of bad casting. I did not pull the rest of the camshaft out. I did loosen the push rods and was able to turn the cam a little in each direction but did not have the right tools to get in there and pull on it. The little bit it did move was smooth and dont think it got seized up in the rear but was told thats what can cause a break in the front of a cam.

Any opinions????

Look for a missing dowl alignment pin.
Common to get caught between the gears and break right where yours did.

Make sure you check for bent valves.

Bruce,

You mean a "woodruff key", off one of the gears, I am not sure what you are talking about.

Can valves be checked without removing the head?

Its the steel pin for the housing aglinment. Over time it becomes loose and can be disturbed when work has been done and is not either lock tited in or staked.

Very common 4bt problem.

Valves cannot be accuratly checked for being bent without pulling the head. Besides this will also allow you to see if any pistons are damaged if they got hit.

The other possibilty is if the fuel pump was not completely flat when mounted and the gear was wobbling. This could have broken the cam shaft by putting too much side pressure on it.

Thanks I am pretty sure the pump was flush and all nuts were tight. I will double check.

I was careful to not disturb anything. I am really shaking my head on this one. Just does not make any sense.

What a mess!

Looks like I am going to have to put a hole in the bulkhead to allow access to remove cam OR I pull boat out of water and pull the engine.

Pull the head which REALLY sucks!

Deal with the tappets being in the way to remove and install new cam (magnets maybe???)

I am going to go throw up now!

Bruce you are talking about what the Dodge Cummins fanatics (like me) call the "KDP", short for killer dowel pin. Common problem on the truck 6BTA 12 valve Cummins engines as well. On the 6B's it normally only wipes out the drive train cover housing...if you are lucky.

Q: What cam shaft did you put in the 4B? Did you go off the engine tag numbers? Was that engine originally an industrial product, or did it come from Cummins as a marine engine?

I'm asking because I believe the industrial 4Bs have a cast cam shaft and the marine versions are forged. That break looks like a cast piece, forged steel breaks typically have much more "tear" indicated and have a twisted look, not quite so smooth. But cam breaks are typically associated with shock loads, not sitting around idlling.

If it is not the KDP as Bruce described, my vote is that "something" restricted the cams rotational moment and the force exerted at the drive gear sheared the shaft. Besides the cam, I would look around for anything else in the drive train that could have stopped the cam shaft. If the pump locked up it could do that to the cam. Inspect the pump and cam gear carefully for indications.

Good luck.

scot i am very much inpressed not many people know the marine cam is forged and 2005 to present " storm block" has much larger journels. the alignment pin is redesighed with a second notch to prevent slipping forward as a matter of fact you have to give some effort to move forward .looks like a small " o" ring attactment.

After a closer inspection since I now have the front cover off I found the woodruff key for the IP is missing.

I cant believe it, I had made sure it was in and had not fallen out but I must not have double checked from the inspection cover after it was in.

I am SURE that stupid key got in the gears and did it. What a costly STUPID mistake on my part.

These are OEM marine units and using stock cam as per CPL for these sn engines.

I found a brand new OEM cam same part number on ebay for 100 bucks, I paid $509 2 yrs ago for the cam I just broke.

Atleast there is one positive thing that happened today.

The engine just stalled at idle. Is there any way that I did not damage any valves. I would like to just throw in new cam and see if it runs OK. If it doesnt than I figure then I would pull the head off. Any chance???

if the valves are bent, you will know right away...it will run rough and even sound a bit off...you can do a compression check prior to firing to see if there is anything amiss....if a cylinder comes back low, don't start it.....pull the heads.....I would also check for any metal particles in the engine from the cam...maybe even flush the engine by spinning the oil pump manually if you can and change the oil....

Seems to me that if some of the valves are bent, the corresponding push rods should be bent of damaged in some way or another. I would certainly check the pushrods.

My 6b's have the Nippo pumps. The gears for the Nippo pumps do not even have a keyway cut into the bore. As I remember the shaft is keyed but not the Gear. Simply the friction from the taper drives the pump.

What pump does the 4 cylinder engines use?

I know it certainly hurt your feeling Frank, just getter going again and tomorrow will be a better day.

hb

frank when you reassemble give me a call we use cam 2 assenbly lube on cam and woodruff key i have a can for you as well as four differant style dial indicator for checking run out on valves .

Thanks Harry and Bob

I was hoping I would wake up today and find out it was yesterday and have a chance to do it all again! LOL oh well!

I removed all the push rods and they are OK. I measured the valve spring heights in the seated position and they are all the same so there is a chance I did not bend any valves. I am going to slap a new cam in and see what happens.

Anybody out there have a trick for holding the lifter tappets up while the CAM is pulled out and new one installed???

I was thinking magnets but I need 8 of them, I was wondering if there were any other tricks out there.

I had no luck finding the woodruff key, I tried for a half hour with a magnet in the sump and poked a scribe in every nook and cranny of the front gear area.



I am greatful that this was caused by something I did and not some seizure that would have had no explanation on a new rebuild that would have hurt my confidence in these engines.

Frank
I seem to remember that the Lifter come all of the way thru the lifter bore......enough that you can get a small hose clamp around it, then tighten it up enough to hold the lifter in place.

I have heard of old timers talk about pulling the lifter up high and then wrapping rubberbands tight enough around the lifter to keep it up and out of the way.

I just hope and pray that the engine that failed is your starboard engine.....otherwise you have my sympathy.

You guys have me scared to death now! ! ! Hope my dowel pins stay in place.

Bruce, Why is this a common problem on the 4's and not necessarily on the 6's?

Keep us posted

hb

Harry, here ya go:

http://www.genosgarage.com/prodinfo.asp ... =TST-KDP03

Use the 94-98 Dodge Cummins 12V piece, those series of Dodge truck motors are nearly identical to the Cummins 6BT marine engines. I "think" this should be a direct bolt in peice, almost everything else is from that series Dodge.

Also,

I measured the valve spring heights in the seated position

Clever boy, I had not thought of that one. Hang in there. the bright side is you will learn your engines even better which will restore your confidence in them.

Its the Port engine gonna be a bastard no matter what. The idea was from the diesel mechanic from the place I work on the side.

He said if the valve heights are all the same then its worth a try to replace cam and keep fingers crossed. I also threw that idea around with a few other mechanics and they agreed it is worth a shot.

Just waiting for new cam to arrive and still figuring out a scenario to hold the lifters while the swap gets done.

Good luck with the new cam. Im pulling for you. You're on your way to being the resident 4BT expert after getting these engines in the boat and rebuilding them. As much as i know about mine i would still be thinking OH S*** what was that! So your ahead of the game and on your way with a solution.

Keep us updated.

Major

Looks like I am going to hold the lifters up with wooden pegs that get lightly tapped into them from above.

Then cam gets removed / installed while pegs are held up by rubberbands.

The procedure is ACTUALLY in the Cummins manual.
still waiting on cam

I am a huge fan of working with Rubber Bands and Bungee Cords...toss in a Roll of Duck Tape and I just get all Giddly ( yeah... I know Duct )

But I am easily amused. (been hearing that alot)

and vise grips and a hammer...

Carl wrote:Roll of Duck Tape

Reminds me of an ole coonass joke.....

One morning Boudreaux was paddling his pirogue down de bayou when he passed Thibeaux camp.

Thibeaux said to Boudreaux, he said Boudreaux...where are you going wiff yo pirogue full of dat duck tape????

Boudreaux replied, Thibeaux....I am going Duck hunting....wanna go??

Thibeaux said, Boudreaux....yo crazy....you can't get no ducks wiff duck tape.

Well several hours later Boudreaux came paddling back up the bayou wiff a pirogue full of dem mallard ducks......Thibeaux jus shook his head in amazment

Da nex morning here comes Boudreaux again, paddling his pirogue down da bayou.

Thibeaux said, Boudreaux???? where you going wiff dat pirogue full of Nutri-Sweet......

Boudreaux said....Thibeaux....I'm going Nutria hunting....you wanna go???

den Thibeaux said to Boudreaux.....you can't get none of dem Nutria wiff nutra sweet.

Well a couple of hour later Boudreaux came padding back up de bayou wiff a pirogue full of nice fat Nutria's......

Thibeaux just shook his head...in disbelief.

De next morning once again here comes Boudreaux paddling his pirogue down de bayou......

Thibeaux looks really hard at the pirogue and said....he said Boudreaux what's dat stuff in your pirogue.

Boudreaux said to Thibdeaux......Thibdeaux thats pussy willow in my pirogue....

Thibdeaux said to Boudreaux......wait a minute while I get my hat! ! ! !

John F. wrote:and vise grips and a hammer...

Almost forgot Cable Ties

frank due to my background and something personel knowing tower 2 of world trade center was coming down and those guys "stuck to it" with everyone in fdny knowing the end was near just rescue as many as you can. that makes you one of the best.a true unsung hero . anything i can help you with say it.
ok forget the novice here is how it is done; get the perfect fit wooden dowel that makes a tight fit in the tappet now pull it up one by one and tape to block .when all tappets are up you pull that cam out. meet me at my boat i will give you the assembly lube.

Thanks guys i will keep you posted I got the CAM just need to find some time to bang it out.

I unfortunately need to cut a hole in the bulkhead to install the cam. It will be going thru the head (bathroom wall). Just what my boat needs another hole.

I am going to take my time on this one.

Is there an access hatch big enough for you to do the job and then cover the hole?

I had to cut a hole in the bulkhead of my head as well. Not for a Cam shaft but to pull the studs out of the water pump pulley. Loosen them up from the engine compartment, then went into the bathroom to pull them out. A small cover was attached when I was done. You gotta do what you gotta do...I knew I wasn't pulling motor to change a water pump.

The v8's were tight when I had them. These 4BT's have so much room in front but not enough for the camshaft. I do have about 1 foot of clearance to the bulkhead up front. What makes it worse is I have to make the hole big enough for the cam gear as well which has to be like 7 or 8 inches diameter.

Oh well. I got the parts just not the time right now.

The reason the 4BT's have more room is because I am using ZF down angle transmissions. They take up so much less room than the velvet drives.

Frank
Be sure to replace the cam bearing.

It was sure to take quite a wallop when the gears fouled and broke the cam.

To the best of my memory it has only one oil hole that must be aligned with the hold in the block.

Just a thought that crossed my mind.....

hb

OK we are now up and running again. The wooden dowels worked great. When I was putting the cam in the thrust plate fell off and went bloop into the oil passage and right into the pan. Something like that is just my luck, I was able to retrieve it with my trusty magnet.

Engine fired right up. I unfortunately have a leak somewhere in the IP. Looks like 2 different high pressure lines are leaking now. The leaky injector pump was the reason this whole disaster started in the first place.

I think taking the lines on and off a few times disturbed something and now there is a pretty good drip. Engines were too hot after test drive today to do anything other than remove the lines and the 2 banjo type high pressure lines that are on the pump itself. I need to see if something is cracked and if not some new copper washers may do the trick. The flare nuts and lines are loaded with paint and may be contributing to them not seating properly.

I was only getting 2400rpms and I think the leaks in the high pressure line may possibly contributing to the top end loss. I did not check the timing through the side cover either, which I will after I repair the leaks.

I guess all in all I should be happy, the cam only cost 100 bucks OEM on ebay.


On a side note I found what was left of the woodruff key that caused the camshaft failure. There is no question it was the cause. I fised it out of the oil pan with a magnet and when I pulled it out it looked like a broken gear with 2 teeth. This key got so smashed when ti went through the gears it actually got pressed into the shape of the gears, I will post some pics of it in a day or two.

That's good news Frank

I remember the begining of this problem.......look at ya now.....you even have a LOT of August left to enjoy the ole girl.

hb