Cm2350 leak down failed

[Tony]

Hello everyone. I just preformed and injector leak down test on my cm2350, It failed horribly. I did run an injector test and it passed. Also there are no codes and truck has 345k miles. Should I replce the pressure relief valve first or buy fuel rail caps to test each injector individually? Is there any other test I should preform?

Thanks in advance.

[Rawze]

relief valve first

[Tony]

I changed the pressure relief valve and the results didn't change. If any of the fuel rail lines are leaking would I be able to see it? Any other test I should do?

More info on the truck: it is demandated. 350,000mi stock fuel pump internals. Never had overhead done. Should I start there??

[Rawze]

next step is to loosen and re-torque all the quell tubes then do the leak test again. Maybe you get lucky and it is simply an improperly torqued feed tube.

.. and no, you will not see fuel anywhere due to leaking injectors etc ... as leaks will drain back into the return lines internally to the head.


After replacing the pressure relief valve, and re-torquing all the feed tubes, and getting the air out of the lines again,. etc.. if it still fails then its time to start capping off up to 3 injectors at a time to find the injector(s) that are leaking.

Leaking injectors are nothing to play with or to ignore. They can cause valve seats to get eaten up, cause a dropped liner or other combustion related damage, and eventual severe engine damage will be the result.

[Rawze]

Also, if it is de-mandated, the have I reviewed your program to ensure it is not harmful to the engine?. That is just as important too.

[Tony]

Yes, you reviewed my program and saved me from doing a VGT delete... lol. After the retorque of the fuel tube nuts and fuel lines. Is there a way to prime the fuel lines/injectors? Also if I cap off 3 lines @ a time do I start the engine and preformed the leak down test the same way? Just running on 3 cylinders.

[tree98]

(11-20-2023 )Tony Wrote:  Yes, you reviewed my program and saved me from doing a VGT delete... lol. After the retorque of the fuel tube nuts and fuel lines. Is there a way to prime the fuel lines/injectors? Also if I cap off 3 lines @ a time do I start the engine and preformed the leak down test the same way? Just running on 3 cylinders.

The fuel system is self priming as long as you have good fuel pressure going into the high pressure pump.

Yes cap off 3 then start it on the other 3 to run the test.

[Tony]

So I started off retorquing the injector tube nuts and fuel lines but still failed the leak down test.

I ended up purchasing (3) 20mm fuel line caps off of Amazon for about $16 a piece. Instead of $140/piece from stealership... I was worried they would be crap but worked awesome.

The engine ran smoother then I anticipated on 3 cylinders.

I ended up narrowing it down to my #5 injector. With #5 capped off the leak down test only dropped 1k psi in a min.

So I know to only use a genuine cummins injector, dealership was about $1450 +core. I will be installing it next weekend unless anyone knows where I can get one for a better price.. lol (only genuine cummins)

[tree98]

(11-27-2023 )Tony Wrote:  I ended up purchasing (3) 20mm fuel line caps off of Amazon for about $16 a piece. Instead of $140/piece from stealership.

This is VERY DANGEROUS!! That fuel rail gets up to 29,000 psi, if one of those Amazon caps fails it could easily kill or seriously injure someone. Isn't your life worth more than $372.00 ?

Glad to hear you found your problem