Threaded Mode | Linear Mode

Valley11 · 01-23-2021, **(Subject: X15 rough idle issues )**

That would make a lot more sense 4000 drop then 21000. I found on quickserve. Would anyone on here now the actual spec for fuel drop spec?

tree98 · 01-23-2021, **(Subject: X15 rough idle issues )**

You need cummins part#4919546. That's a cap so you can cap off the fuel rail to that injector and run the pressure test again to see if it passes without that injector hooked up.

Rawze · 01-23-2021, **(Subject: X15 rough idle issues )**

(01-22-2021 )Valley11 Wrote: Today I did an injector leak down test and it passed built to 29000psi dropped to 23000psi after 30 seconds allowance is 21000psi drop. Check low pressure side of fuel system restriction pressure lift pump pressure all passed. Did cylinder cut out test found that #1 cylinder cutting it out the haze out of the pipes would clear up and come right back with it back on. Cutting out any other cylinders the haze was always there. According to that o would say there is an issue with #1 cylinder. That’s as far as it got today the shop was full of raw fuel by the end of all that

(01-23-2021 )Valley11 Wrote: That would make a lot more sense 4000 drop then 21000. I found on quickserve. Would anyone on here now the actual spec for fuel drop spec?

It is bad. Quickserv is wrong with those specs, it has been discussed on here before. It should not drop more than 4,000 psi in 60 seconds.

The original spec was 4,000 in 60 seconds. it got changed by QSOL for some reason or another (likely too many warranty claims?) and I have never agreed with this because I've seen people with too many issues when they are more leaky than about 4,000 psi or so.

In all actuality, on a perfectly healthy system, it is normal for it not to drop at all whatsoever in the first minute or so... but the old quickserv instructions used to say 4,000 psi in one minute .. but then I think they must have gotten tired of warranty claims or something so they made it that ridiculous number they have now ... and it is for sure not good for your engine for them to be that leaky. fuel impingement. dry fuel buildup in the crown of the piston(s), and all sorts of other issues over time.

start by replacing the relief valve at the end of the fuel rail. They tend to get leaky especially for people who have turned up the HP in their engines or are pushing them hard a lot. Next would be to re-torque all the feed-tubes that feed the injectors and then do the leak-test again. - After that, if it is still more than 4,000 psi in one minute, you need to find what injector is leaking because it is leaking into the cylinder(s) and this is bad for the engine and pistons.

JimT · 01-23-2021, **(Subject: X15 rough idle issues )**

Sounds like you already determined that injector/cylinder #1 is the problem area.

Just for reference I did a rail leakdown test a few weeks back. Lost about 100psi in the first minute, after 5 mintues I was down about 300psi to end up around 29,000psi. A good functional system will have little to no pressure loss.

Valley11 · 01-26-2021, **(Subject: X15 rough idle issues )**

Going to find out more tomorrow but turns out so far the valves were all tight might have started to wear into the head. not sure if just exhaust or intake also. Was told must have been getting too hot with the tune going to get a new file with proper programming. See what else the mechanic has to say.