Diesel Engine Question

[FastRam]

I have a Onan generator set at a site. The set uses a Cummins diesel engine and a 550KVA rated alternator (generator rating). Due to low electrical demand the set is used at less than 15% of capacity. The engine has 700 hours on it. My questions concern the engine. I don't have engine data yet but the set has been experiencing rear main seal failures -- we're on the 4th one in 6 months. The seal fails and splashes/sprays oil all over the alternator and its cooling fan. Also, we have lost on several occasions alternator and water pump belts as well. During the 2nd servicing, a Cummins tech came in and before they replaced the rear seal, he scuffed up the crank journal with sand paper. I assume they did this to try and get the seal to seal. I did not witness this and I don't know if they used emory cloth or plain old sand paper. My guess is the latter, i.e. sand paper, was used as we are now on the 4th seal. I believe they should have used emory cloth, assuming Cummins approves of this method to try and help improve seal performance.

Is there any way to fix the scoring marks the sand paper left behind, coming short of replacing the crank? It keeps leaking and each time others make a decision to try and replace the seal... Also, we are bringing in another Cummins team to check the rotating assembly for balance and vibration, bearing clearances, etc. My other question is if the engine is lightly loaded, e.g. below designed minimum load, can accelerated wear occur to rotating and reciprocating parts, e.g. bearing/cap wear, etc.?

 

[includemeout]

I have a Onan generator set at a site. The set uses a Cummins diesel engine and a 550KVA rated alternator (generator rating). Due to low electrical demand the set is used at less than 15% of capacity. The engine has 700 hours on it. My questions concern the engine. I don't have engine data yet but the set has been experiencing rear main seal failures -- we're on the 4th one in 6 months. The seal fails and splashes/sprays oil all over the alternator and its cooling fan. Also, we have lost on several occasions alternator and water pump belts as well. During the 2nd servicing, a Cummins tech came in and before they replaced the rear seal, he scuffed up the crank journal with sand paper. I assume they did this to try and get the seal to seal. I did not witness this and I don't know if they used emory cloth or plain old sand paper. My guess is the latter, i.e. sand paper, was used as we are now on the 4th seal. I believe they should have used emory cloth, assuming Cummins approves of this method to try and help improve seal performance.

Is there any way to fix the scoring marks the sand paper left behind, coming short of replacing the crank? It keeps leaking and each time others make a decision to try and replace the seal... Also, we are bringing in another Cummins team to check the rotating assembly for balance and vibration, bearing clearances, etc. My other question is if the engine is lightly loaded, e.g. below designed minimum load, can accelerated wear occur to rotating and reciprocating parts, e.g. bearing/cap wear, etc.?

Under loading is not the problem. The crankshaft was most likely bad from the getgo and the sand paper is just making it worse (cheap way not to warrenty the entire unit.) I would have them replace the whole thing.

 

[dnz28]

Been working on those gensets for while they should have a seal service set that includes a wear sleeve(if the crank is worn, groved, it covers it) Also depending on who services your engine they NEED to check the bell housing for being off center(big problem i have seen) and relocate the dowels to align and correct the offset. I can guarentee thats the problem. k19s are often missaligned. A light load causes carbon build up, but no real wear and tear

 

[perk_1405]

I have a Onan generator set at a site. The set uses a Cummins diesel engine and a 550KVA rated alternator (generator rating). Due to low electrical demand the set is used at less than 15% of capacity. The engine has 700 hours on it. My questions concern the engine. I don't have engine data yet but the set has been experiencing rear main seal failures -- we're on the 4th one in 6 months. The seal fails and splashes/sprays oil all over the alternator and its cooling fan. Also, we have lost on several occasions alternator and water pump belts as well. During the 2nd servicing, a Cummins tech came in and before they replaced the rear seal, he scuffed up the crank journal with sand paper. I assume they did this to try and get the seal to seal. I did not witness this and I don't know if they used emory cloth or plain old sand paper. My guess is the latter, i.e. sand paper, was used as we are now on the 4th seal. I believe they should have used emory cloth, assuming Cummins approves of this method to try and help improve seal performance.

Is there any way to fix the scoring marks the sand paper left behind, coming short of replacing the crank? It keeps leaking and each time others make a decision to try and replace the seal... Also, we are bringing in another Cummins team to check the rotating assembly for balance and vibration, bearing clearances, etc. My other question is if the engine is lightly loaded, e.g. below designed minimum load, can accelerated wear occur to rotating and reciprocating parts, e.g. bearing/cap wear, etc.?

if the unit is not used under full load then it needs to be load banked at least once a year. this keeps it from wet stacking and makes sure it will handle rated capacities when needed. as for cummings techs we (sure-gen the company i work for) have got plenty of calls from customers that had cummings atlantic and were not satisified. where are you located?

 

[breederofkoi]

Been working on those gensets for while they should have a seal service set that includes a wear sleeve(if the crank is worn, groved, it covers it) Also depending on who services your engine they NEED to check the bell housing for being off center(big problem i have seen) and relocate the dowels to align and correct the offset. I can guarentee thats the problem. k19s are often missaligned. A light load causes carbon build up, but no real wear and tear

I'll have to side with you... Check the bell housing for alignment (possibly bent or missing dowels) & install a speedy sleeve to fix the scoring on the crank.

 

[breederofkoi]

As far as throwing belts... I'm assuming your talking the the engine belt (on the front cover of engine). Make sure the tensioner swings freely and doesn't bind up at any spot in the swing path (it tends to take a little "umph" to move it, theres a descent amount of force on it). As a general rule, whenever I replace a belt, I change the tensioner too (cheap insurance). Also, take some string and check the alignment of the pulleys or you can eyeball it if no string available.. And finally, when installing belts, Theres usually 1 or 2 bolts on the front cover that have a "belt guide" spacer on them, should be located on the front cover bolts around the bottom of the crank pulley (make sure there not missing).

 

[FastRam]

Thanks for the help guys. Great suggestions and advise. On the load bank. I found out late yesterday it exists -- the problem is nobody wired it up when the set was installed :dontknow: As soon as we get the seal sorted, the load bank connection is priority numero uno.

 

[Slitherbeast]

If you changed the seal 4 times and it still leaks , It's not the seal. Must be a crank problem or simply to much crankcase pressure.

 

[ZCx]

I'll have to side with you... Check the bell housing for alignment (possibly bent or missing dowels) & install a speedy sleeve to fix the scoring on the crank.

if you are talkin "FLYWHEEL HOUSIN" then & if its out of round, it will cause the equipment that is bein driven to have probs not the rear crankseal. Cummins uses a seperate seal carrier.

check for excessive crank case pressure, seal carrier out of round, excessive bearin clearences.

if its not a seal/wear ring set up, then a speedy sleeve is whats needed

 

[bigike]

Take some 180 and 320 emery cloth.

Get a bucket of mineral spirit's, Hit make sure the 2-3 foot strip is nice and soaked, remove the rear main.

wrap the emery cloth around the journal, two people one on each side. pull the paper back and forth. Sanding a main or rod journal is done all the time.............. all the time. This is a small engine, i don't know how easy it will be. The rear main is always the hardest.

Next If you only load this poor thing to 15% capacity, you need to invest in a load bank from cat, rent it once every two months and open that baby up!

450 kw..... Kind of small for lapping in the journal, the trick is using a lubricant like mineral spirits or wd40 if you have to.

 

[breederofkoi]

if you are talkin "FLYWHEEL HOUSIN" then & if its out of round, it will cause the equipment that is bein driven to have probs not the rear crankseal. Cummins uses a seperate seal carrier.

check for excessive crank case pressure, seal carrier out of round, excessive bearin clearences.

if its not a seal/wear ring set up, then a speedy sleeve is whats needed

depends on which motor you got.. the little cummins 3.3 doesn't use a seperate seal carrier. rear main installed in bellhousing. Have had to replace a few that cracked.