ISX high pressure system leak down test

[Margeetus]

Hello everyone,
I have an Isx15, cm2350 x114b that I'm trying to perform the injector leak down test on. My problem is getting Insite to reconnect after killing the ignition and switching it back on - it won't reconnect unless I exit the leak down test in Insite. Is this how it is supposed to work?

Seems like I saw a video somewhere with this test being performed but can't find it now.

Thanks, Festus

[J_Rok]

(02-05-2025 )Margeetus Wrote:  Hello everyone,
I have an Isx15, cm2350 x114b that I'm trying to perform the injector leak down test on. My problem is getting Insite to reconnect after killing the ignition and switching it back on - it won't reconnect unless I exit the leak down test in Insite. Is this how it is supposed to work?

Seems like I saw a video somewhere with this test being performed but can't find it now.

Thanks, Festus

Hello, here’s the link to the leak down test by Rawze, as for why it won’t connect hopefully someone else will chime in that can tell you more.
https://rawze.com/forums/showthread.php?...3#pid75483

[Rawze]

(02-05-2025 )Margeetus Wrote:  Hello everyone,
I have an Isx15, cm2350 x114b that I'm trying to perform the injector leak down test on. My problem is getting Insite to reconnect after killing the ignition and switching it back on - it won't reconnect unless I exit the leak down test in Insite. Is this how it is supposed to work?

Seems like I saw a video somewhere with this test being performed but can't find it now.

Thanks, Festus

the leak-down test screen itself will fail as soon as the engine stops,... but the fuel pressure monitor screen will keep reading pressure. - That is why you need to open both windows like the video shows.
https://rawze.com/forums/showthread.php?...3#pid75483

[Margeetus]

Thanks for the quick reply everyone. I ran the leak down test and started at 29,000 PSI ended at about 4,000 PSI so it looks like I got a leaker. I ran the return flow test for the injectors and got about 30 ml collected. Also ran the relief valve test and it was dry no leakage there. Next test was the pump return flow test and it was within spec, 450ml, iirc.

Symptoms are loss of power when it heats up, and what appears to be missing, running rough. No codes.

I did have to replace #5 injector recently, as it stuck open and filled the cylinder with fuel.. Any ideas? Thanks!

[Rawze]

(02-06-2025 )Margeetus Wrote:  Thanks for the quick reply everyone. I ran the leak down test and started at 29,000 PSI ended at about 4,000 PSI so it looks like I got a leaker. I ran the return flow test for the injectors and got about 30 ml collected. Also ran the relief valve test and it was dry no leakage there. Next test was the pump return flow test and it was within spec, 450ml, iirc.

Symptoms are loss of power when it heats up, and what appears to be missing, running rough. No codes.

I did have to replace #5 injector recently, as it stuck open and filled the cylinder with fuel.. Any ideas? Thanks!

you can cap off up to 3 injectors at a time to help find it.

[Yauchout]

(02-07-2025 )Rawze Wrote:  

(02-06-2025 )Margeetus Wrote:  Thanks for the quick reply everyone. I ran the leak down test and started at 29,000 PSI ended at about 4,000 PSI so it looks like I got a leaker. I ran the return flow test for the injectors and got about 30 ml collected. Also ran the relief valve test and it was dry no leakage there. Next test was the pump return flow test and it was within spec, 450ml, iirc.

Symptoms are loss of power when it heats up, and what appears to be missing, running rough. No codes.

I did have to replace #5 injector recently, as it stuck open and filled the cylinder with fuel.. Any ideas? Thanks!

you can cap off up to 3 injectors at a time to help find it.

thought i would add to this i have had good luck on cm2350's starting and running with 5 of the 6 injectors capped to help narrow them down

[Margeetus]

[quote/]
thought i would add to this i have had good luck on cm2350's starting and running with 5 of the 6 injectors capped to help narrow them down
[/quote]

Wow, the 1 cylinder ISX! 8-) I didn't have to go down that far.

I started off capping cylinders 4&5, as I had recently replaced #6 and re-ran the leakdown test and fuel pressure stayed around 30k psi for the full test. It was weird, the fuel pressure was right around 29,000psi while running, but actually increased to a bit over 30,000psi when I shut it down. Maybe the fuel pump stroked and the injectors didn't fire right as I shut it down?? Kind of strange behavior.

I then reconnected #5 and it was still sealed, so #4 was my leaker. I replaced #4 and the beast is running happily now! Thanks Rawze for the great information!

I find it amazing that 1 leaky injector was causing it to run this bad. I understand that it would be down on power, but it was dropping down to almost nothing and had horrible vibrations... The ECM must be doing something to the other injectors to try to compensate, or making it run so bad that you have to stop and fix it? I had watched rail pressure previously with the bad injector and it wasn't running low or anything. There wasn't any strange knocking noise or anything like that I could hear. Anybody know what exactly is going on with a leaky injector?

Thanks,

Margeetus

[Rawze]

(02-13-2025 )Margeetus Wrote:  ...
It was weird, the fuel pressure was right around 29,000psi while running, but actually increased to a bit over 30,000psi when I shut it down.
...

That is because of expansion of the fuel as it heated got hotter and was absorbing heat from the engine/rail/pump after shutdown.

its nice to see that you finally found it.