Injector Cutout Test for evaluating a used engine?

[rv_safetyman]

Many of you have followed my story about my troubled Series 60 engine (http://www.busconversions.com/bbs/index.php?topic=12599.0)

In a thread about Sean Welsh's  turbo problems (http://www.busconversions.com/bbs/index.php?topic=12676.0) he posted the text quoted below:

This morning, during my third and final warm-up/cool-down cycle, I plugged in the DDR to check on everything.  Specifically, I checked injector response, which looked good on all eight cylinders, ranging from 1.07 to 1.17.  I also ran the injector cut-out test on all cylinders at idle as well as 1,000 rpm, and all injectors elicited a response, with pulse width increasing by 0.2 to 0.4 for each cylinder.

For those unfamiliar, what this latter test does is to first report the amount of fuel being provided to the cylinders in the form of "pulse width" (PW), the amount of time the injectors are commanded to inject.  Then it shuts off the injectors one at a time and reports the PW as each injector is off line.  The idea here is that when a cylinder that was contributing real work gets turned off, the DDEC will have to increase the PW to supply more fuel to the rest of the cylinders to carry the load.  If you turn off one injector, and there is no resulting change in PW, that means that that cylinder was not doing any work, which could mean a bad injector (or a number of other problems).

I am interpreting the results, being fairly consistent across all cylinders, as meaning that I still have all eight injector tips, and all the exhaust valves are intact.  I'm not conversant enough with these sorts of tests to rule out any other problems (low compression, marginal injector, etc.), but I am fairly confident at this point that the turbine failure was not due to FOD originating in the engine.

That got me to thinking about using this test to check out a used engine to replace my dead Series 60.  I have a Pro-Link Graphiq with the DDEC III/IV card and it looks like I can run the same test.

I would like to get comments about how good of an evaluation test that would be.  Also, do any of you have advice about how to properly evaluate the test results?

Appreciate any advice.

Jim

[Zeroclearance]

With the engine out and sitting on a skid one could perform a leakdown test to gauge the engines health.   You will have to pull the injectors and rotate each cylinder to TDC..    You will quickly find out the condition of the rings, intake and exhaust valves and head gasket/liner.

If the engine is/was running you would be able to run the engine on a dyno and run all the mentioned tests and check for rated HP and torque.

[luvrbus]

Jim, what good will a cut out test do except locate a bad injector it is not going tell anything other than the electronic part of the injector.
Cole is working on the info for you on the 2 engines and hopes to have it all by Monday then I will foward his email to you.       

good luck

[rv_safetyman]

Kevin and Clifford thank for the replies.  What does it take to run a compression test?  I assume that a special gage is inserted where the injector goes.  Do you turn the engine over with the starter?  Does engine temperature affect the reading?  Is there a "goal" compression or are you just looking for differences?  Have done the test a ton on times on a gas engine but not a diesel engine.

Next question, I changed from doing a compression test on gas engines to a leak down test.  Is there a similar test for diesel engines?  Can I use the same gauge with an adapter?

As you can guess, I am now paranoid about getting a decent engine.  One of the engines I am looking at does not have an ECM, so there is no way to verify the reported very low mileage (wrecked bus that was in service less than four years).

Clifford, I really don't know what the cutout test would show.  From Sean's comments, it sounds like it could be a good piece of information.

Another reason I ask, is that I was going to sell the Pro-Link as a part of gathering funds to buy an engine.  I really did not want to do that, but sometimes you have no choice.  So the big issue is whether I should keep it until after I check out the engine(s).

Jim

[luvrbus]

Jim, the compression test for a 60s is a all day job removing each injector and re timing it will tell if you have bad valves, cracked head or bad compression rings and that is about it.
I would build me a stand to set the engine on and install my ECM on the engine you are looking at run it.The best way I think not a hard thing to do just watch giving it full throttle they will take off don't ask how I know that part.    good luck

[Zeroclearance]

Jim, there is a difference between a compression test and a leak down test.   I don't place much value in a compression test.  The leakdown test we typically start with 100 psi and pressurize the cylinder.   The percentage of leakage from 100 psi will tell us the health of that hole.   Rings, intake valves, and exhaust valves.   You can also use a boroscope and look down each hole to view the cylinders/pistons for any damage or extreme wear.   

[Zeroclearance]

Jim, I would try to structure the purchase deal with some sort of warranty.   30 days or "X"  amount.

This will give you the time to pull the pan and roll new bearings if you want.   You can also pull the valve cover and check the camshaft for wear.

I should have explained and answered your question about the leakdown test.   When we pressurize the cylinder we are finding out the mechanical health.   In theory we should only have around 2 to 3% of air leaking out the rings, and valves.   At 5 to 6% we have some wear.   10 to 15% we have to address looking at the valves or rings.   The leakdown test will tell us which component is worn.  This includes valve guides.   You will want to listen to ANY air leakage coming out the exhaust/turbine housing>this will point to worn exhaust valves.   Air/hissing out the intake will lead to a failed/bent intake valve.    You will want to pull the oil drain plug>oil should be drained..   If you hear any air in the basement and the gauge is down you have a bad ring pack. 

A compression test is a starting point, I don't even bother with them these days.  It is the leakdown test and dyno test that really shows the condition of the engine.   Being able to run the diagnostics and seeing the engine functions while under load with oil samples will usually give one all the data for a good engine.

[rv_safetyman]

On the leak down test, I assume I can use my present setup and buy/make an adapter to fit in the injector hole.  Are adapters available?

On a gas engine you have to be very careful to have the piston at top dead center, or the pressure will move the piston down the cylinder with a pretty off force.  I assume that is also true with the Series 60.

I don't have a borescope.  Almost bought one for a consulting case I was on, but it settled before I could justify the cost.

Jim

[Sean]

Jim, what good will a cut out test do except locate a bad injector it is not going tell anything other than the electronic part of the injector.

That's not entirely true.  The cut-out test will tell you if a cylinder is not contributing its fair share of the work for any reason at all, such as little or no compression.  In fact, if the cut-out test reveals a bad cylinder, you can not assume it is an injector problem -- you must investigate further.  The injector response time test would potentially reveal electronic injector problems.

-Sean
http://OurOdyssey.BlogSpot.com

[Zeroclearance]

Jim;

I use a Snap On leakdown guage.   I have various adapters, I have made a few >cutting/machining up a old injector, finishing up with a little tig welding.   

Jim I have a later model DDEC IV S60, there are a few updates that I have to 225K.    Feel free to get ahold of me to discuss a few things.   

Kevin

[NJT 5573]

I can see a leakdown test with a gasoline engine, they are small and tightly built. I have my doubts though with the diesel. But I've never done one. Seems like an awfully lot of work. May just shoot alot of air into the pan with a cold engine. Last I knew the big diesel pistons don't get round until they are up to temperature.

I don't believe I would change out the mains or rods either unless there are a lot of miles on the engine. Everything costs more money. How did the bearings look on the 650,000 mile engine when it came apart? Should give an idea of where you are with another engine. The 60 series is not known for bearing failures.

The cutout test seems easy on the face of things, but it still takes some time and money to get an engine running in a stand. A dyno would be nice to, but that won't be cheap either. Put it in, do the cutout test and if it fails,take it back I guess. The labor to put it in probably isn't a lot different than trying to run it on a stand.

Any engine can have a failure, It's impossible to see the future. I was down at the DD Dealer yesterday and they have a lot of used up series 60's sitting out in the sun. Ease of repair and cost is one of the most important issues when you pick an engine that you will live with the rest of your life.

Personally, I would put the old one back togather myself at home. Then you would be ready for the issues that are to come and have the knowledge to deal with them. You would also be the resident expert on the bus boards! Your head was good, you can touch up your valves by hand with some lap compound if you want and buy a couple new or used valves if needed, and if you find a guide or two that are a little sloppy, you can knock out the old one and put in a replacement.

The camshaft is a little complicated, but if you send the block out to have the 2 counterbores cleaned up you can pay to have the cam bearings changed out, or you can have the shop send you a mechanic to do the counterbores at your shop/home and only do the cam bearings if they need it. They could also install the liners and you could pretty much handle it from there. I think you can just change out the bad cam follower and leave the rest if they are OK.

I might advertise for a part time DD mechanic in your area, people are out of work and you may find someone to sort your good parts from the bad and put it back togather for you pretty reasonable, then you would know what you had and know alot about it for future reference. The 60 is a lot easier to repair than a 2 stroke.

I'd probably just take a good look at the camshaft on the used engine, and take my chances. Who ever is selling should have already checked the cam and main/rod bearings though, most all salvage yards do. I have dealt with American Truck Salvage in Phoenix, they usually inspect the internals on all their engines. They have an engine shop, a tranny shop and a rear gear shop on the premises.

They have a 12.7 for $8,000 that has 170,000 miles on it and if they have not looked at it I believe they would open it up for you on their dime and show it to you, no charge if you told them you would take it if it looked good.

[luvrbus]

Sorry Sean it will locate a missing cylinder but won't give Jim the info he is looking for Zero's method is the only way to determed that by pulling the injector and testing.
Jim I also have the test equipment if you need it you are welcome to it Mac has a set that cost less than Snap On and I have saw guys take a old injector body and make their own.
That test is a luxury us 2 stroke owners don't have we have a compression only at 900 rpm removing 1 injector at a time then replace it time it go to the next one.
If you want to check on the one at American Truck I'll be glad to drive to Phoenix and do some checking they are good people they may even run for you on a stand they did for me on a 8v92   good luck Jim

[Zeroclearance]

NJT,  I have pulled the leakdown on a fair number or Cat's  3304, 3306, 3406 B,C D398, D399..   I have NOT done it on my own Series 60.   But that is the only method to gauge the health of a engine without running it on the dyno.    An engine running on a test stand without any load will just prove that it can run and idle.   

[NJT 5573]

Kevin,

I agree, that is a good test procedure. The problem I see, is weather or not it's realistic for Jim. To put 2 or 3 engines on a stand and pull the heads/injectors down and put them back togather ain't going to be cheap. We got a guy here that is thinking about selling his tools just to purchase another engine. I'm with you, we would certainly like to see him get a good one, but can he afford to spend $1000 or more to inspect each of the available engines?

Some people may prefer to sell to someone else rather than have what they believe is a good engine pulled apart and possibly not put togather properly again. Is Jim going to replace the oil at his cost? He has to spin them over and coat the cylinder walls to get a good reading. Can Jim afford to haul them down to Detriot Diesel and pay a hundred an hour? If there is some carbon stuck under a valve, you would reject a good engine, and thats not unusual. Probably better to pay for a dyno.

I don't think a leak down will spot a wearing cam lobe though, or worn rods or mains. Mostly I think valves and ring or piston damage.

If you offered to jump on a plane for free and the seller agreed you could really help out on this one. If Jim was qualified, he would be repairing his old engine.

I think he is in a position of having to trust the seller and believe the information furnished about each possible engine. Next comes the sellers reputation. If they deal constantly in these engines I would expect a much better outcome if there were issues. They also have a reputation to maintain or in todays world they won't sell alot of engines if the word were to get out that they ran alot of scams. A big outfit like American could afford to hand Jim another engine if they had/wanted to, can the other sellers?

Thats why I suggested American. I also was struck by the picture of the engine they have for sale. The block was unpainted, making me think that it has been hot tanked and likely had machine work, more so than a supposed rebuild that is still wearing the factory paint. I'd still try to find out who did the rebuild and verify DD or aftermarket rebuild kit, but I would chose a rebuilt that has seen a hot tank before one that has not, even though it probably doesn't guarantee anything. Might want to ask about the crank to since it has been out of the unit rebuilt. Turning it won't hurt it any though, but I would like a simple .010 cleanup or nothing under ideal circumstances. Might shy away from a .030 crank, but the engines that are inframe rebuilt have certianly not had the crank clean up turned or crack checked at all, and leak testing won't get you close to any of these issues.

Larry

[Zeroclearance]

Larry, in the end it is Jim's choice.   The economy is in the toilet and these truck salvage companies have to be flexible.   They can't jsut say>>  it's only got 200K on the clock and it will be fine..   It seems like yesterday that Jim was writing about his install.   The pain to go thru this twice isn't fun.  I would spend and negotiate with the seller to do a leakdown test.   Carbon between the valve seat will and should be dislodged by rotating the engine a few degrees and re-pressurizing the cylinder.   And BTW, I have never had carbon under a valve/seat and got a mis-reading using this method.   Anotherwords if you have 5 cylinders reading between 4 and 6% leakdown and then you hit one with 24%..   You have to question what is wrong.   Rock the engine off TDC if the air is coming out the exhaust valve.    Put the air back to the cylinder >  you will dislodge the carbon.   

Most of these wrecking yard engines are exposed and can be serviced.   From my very first post,  a leakdown test and bearing inspection will a oil sample will quickly slant things in your favor and give you some piece of mind.   

These test will cost you some monies.  Inventory is high right now.   There should be a salvage company that is willing to work to a higher standard if the customer is wanting to pay some monies.   They don't want to be selling junk.   

In the end, paying a little now vs having a engine fail down the road just doesn't make sense.  The other option is to pay more monies for a low mile engine.    Larry I do not disagree with all of your points, (exception> I wouldn't rebuild his engine> unless he bought a recon engine block machined back to std/std)   Regardless we feel Jim's pain..