Odd leakdown test results...

[dhirocz]

So on Wednesday I did an injector leakdown test with the Cummins tool. It showed me I had a pretty healthy leak coming from the back bank, so I put an injector on order. Engine was cold at this time.

Today, I did the test again to verify which injector it was, and I cannot get it to leak. At all. Both banks are solid as a rock. I did notice though, the front metering actuator was a bit warmer than the rear.

Is this a normal occurrence? I just ran the test, engine is still warm from driving home however...maybe 140 degrees.

Mileage has dropped again recently, but aside from waiting for it to cool off again and hoping it leaks, what else can be done?

[hhow55]

The very same happened to me. Are you turning motor over, with the ignition first. Then bar the engine?.

[dhirocz]

I barred the engine over. Alot. I got no response...so I spun it over (ecm unplugged) to replicate my results on Wednesday with no luck, no bubbles.

I then checked the front bank in the event I was mistaken. Again, no dice.

Right now the plan is to go out in the morning and run the test again with the engine cold.

To answer your question, when I checked it the first time, I spun it over to verify there was a leak before barring it, which is how I knew it was leaking on the rear bank.

[Hammerhead]

A cold test causing a leak may be the sign if an injector pintle & seat starting to leak, however at warm temps it seals up.
Not sure what your mechanical aptitude, but I believe it was Aussie ISX (?) Had a thread about dismantling 871 injectors & using toothpaste to lap them in and reseal them.
If this is in your wheelhouse and you'd like to try it, I have tools (yes the injector dis&assembly tool) and would very much be interested in experimenting with you...

[dhirocz]

Yeah I'm interested... fortunately I can swap it out and not have downtime since I have spares.

I know it's not the same as a reman injector, but I'm always willing to learn more about these things...and if it buys more life per unit it could very well be worth learning. I remember seeing some Cummins documents regarding disassembling and reassembling injectors.

[dhirocz]

No dice. Now I can't replicate the leak. No bubbles at all.

Is it possible as these things wear that some trash might get into the tip and 'temporarily' cause a leak? Would some power service possibly fix this? I ask because my mileage has gone down lately... eventually the fuel cost will replace the bad injector anyway, but I'd rather not just throw parts at it. Who knows, my 3 month old #6 could be where the leak is too.

I did run some tests with insite. Nothing out of the ordinary. It will run on all 6, one at a time. All holes pass the cylinder performance test. The only thing I notice is it runs a bit rougher on 1,2 and 3 compared to the rear bank, which I would say is probably a sign of actuator wear. 4,5 and 6 runs smoother.

I might swap the actuators around and see if it stays that way or if it flips around. I'm getting 5.3 mpg right now, 80 miles a day, 50% loaded miles, down from the 6.8 I was at before. Half stop and go, 10 lbs of boost or less, all 50 mph or below.

[Hammerhead]

(09-09-2018 )dhirocz Wrote:  No dice. Now I can't replicate the leak. No bubbles at all.

Is it possible as these things wear that some trash might get into the tip and 'temporarily' cause a leak? Would some power service possibly fix this? I ask because my mileage has gone down lately... eventually the fuel cost will replace the bad injector anyway, but I'd rather not just throw parts at it. Who knows, my 3 month old #6 could be where the leak is too.

I did run some tests with insite. Nothing out of the ordinary. It will run on all 6, one at a time. All holes pass the cylinder performance test. The only thing I notice is it runs a bit rougher on 1,2 and 3 compared to the rear bank, which I would say is probably a sign of actuator wear. 4,5 and 6 runs smoother.

I might swap the actuators around and see if it stays that way or if it flips around. I'm getting 5.3 mpg right now, 80 miles a day, 50% loaded miles, down from the 6.8 I was at before. Half stop and go, 10 lbs of boost or less, all 50 mph or below.

The pintle is basically a needle, and the outer portion of the tip on the internal circumference is a seat...
Start with an overhead, making sure your injectors are set properly.

[Rawze]

(09-09-2018 )dhirocz Wrote:  No dice. Now I can't replicate the leak. No bubbles at all.

Is it possible as these things wear that some trash might get into the tip and 'temporarily' cause a leak? Would some power service possibly fix this? I ask because my mileage has gone down lately... eventually the fuel cost will replace the bad injector anyway, but I'd rather not just throw parts at it. Who knows, my 3 month old #6 could be where the leak is too.

I did run some tests with insite. Nothing out of the ordinary. It will run on all 6, one at a time. All holes pass the cylinder performance test. The only thing I notice is it runs a bit rougher on 1,2 and 3 compared to the rear bank, which I would say is probably a sign of actuator wear. 4,5 and 6 runs smoother.

I might swap the actuators around and see if it stays that way or if it flips around. I'm getting 5.3 mpg right now, 80 miles a day, 50% loaded miles, down from the 6.8 I was at before. Half stop and go, 10 lbs of boost or less, all 50 mph or below.

There are a lot of things that cause fuel mileage to change that have nothing whatsoever to do with injectors,.. just saying.