How do I troubleshoot low rail pressure faults FC 559
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- Опубликовано: 28 июл 2024
- Travis has put a lot of $$ into his fuel system and is still having the same problem after three shop events. Let's take a look at the steps that should be followed in solving this issue. In this case his problem shows up on a dyno when the engine is commanding maximum fuel pressure but cant make the requested pressure.
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Nice mid-week treat! Nice of you to go to all of the trouble of making a specific video to help a viewer, hope he gets it figured out. Solid advice on getting test results, and measure what is in spec and what is not. I have been known to roll down the road with clear tubing and pressure gauges tucked under the windshield wipers.
We had a counterweight truck that could not make a trip without logging 559s. We put gauges on and ran the lines into the cab for the driver to watch and note reading when the fault went active. I think the gauges were on it over a month. Our counterweight trucks are paired to units in the taxi fleet. (rubber tire cranes we can drive to jobs). check out LTM 1650-8.1
I like to start on the fuel tanks first and move up to the engine, isolate pickup tubes that crack, check fuel lines with the clear site glass for air bubbles. Then return flow. Fuel is such a long diagnostic test scenario, and so many steps. Thanks for the post about the fuel head test tubes, I didn’t know about those. Great video Joe.
Thanks so much for making this video and explaining some of these tests that they've been doing for me.
I know there was some junk in that screen and that made us look at the suction lines. They were in bad shape and replaced but didn't fix my problem.
Im waiting to hear what they found by pulling the fuel pump today... hopefully some answers and a repair that works.
Once again thanks for this video. Ive got 3 of these engines and after this recent problem....I decided that I need to learn some of the troubleshooting tests and maybe save some money next time!
Just adding:
It is an ISX15 2350
And the top of the pump was rebuilt with parts 1-6 in that picture. He said he pushed down on the plungers to test the check valves and it was good...so assumed they were ok.
if its sucking air you wont have high restriction, you must install a sight glass to check for air, isolate each tank one at a time, and run a line from bucket/tank, paccar products have a problem with the suction tube cracking in the tank, they have a repair fitting to fix it, if its a newer engine bypass that stupid fuel return mixer,
Hey Joe I been running into an issue as well. I have a fault code SPN157 FMI18 .. there no active code it begins to come on as soon as the truck comes up to 170 degrees in the normal temp the motor then it derates and I loose power and I can not get over 50mph and it gets weaker even on smaller hills. It runs like that for 30 minutes then suddenly the power comes back. Lately the code comes back 1 hour later and derates again. If I am driving on streets and I come to stops signs or red lights my truck will turn off. The biggest issue it’s that the fault code won’t stay on. Because once I pull over let it idle 10-20 seconds later the check engine turns off. I have changed many things on this truck had them re tune it 3 times but this issue is been on going on for 5 months.
Today I took to the shop had him do the diagnostic test while on the Cummins software . The command went up to 29000 psi the pump raised up 29000psi and then flexed from 28900-28990. Then he checked the tolerance on the injectors and 1-4 all came in at 641 and but 5 and 6 came in about 637.
At this moment they are checking any leaks they checking the tank. They. Don’t have these tools to check the lines At this time I been fighting this issue since sept 2023. I have and isx CM2250..
I am lost and I can’t find a shop they can conduct this kind of test. I am located in Chicago. My name is Freddy.. thank you
They need to put a fuel restriction gauge at the inlet of the gear pump or at the inlet where fuel enters the number 10 fitting on the side of the engine. Then put the dump line on the filter (.043 oraficed line) Then use insite to put the engine in dyno mode ( this allows it to rev to 2100 rpm. you dont need to be on a dyno it is just a software override. Run it up to 2100 for at least 5 minutes. It would be best if it was hot when you did this. so get all the tooling on except the dump line and let it run outside a half hour at 1250 rpm. Then do the checks at 2100. Look for air in the dump line and watch fuel restriction. It should not go over 8.5 inches at the inlet to the engine. Normal is about 3.5-5 inches of restriction at 2100 with a dump line on. When problems only happen hot and stalling is involved it can be a swelling or flap in a fuel hose. if you have plastic fuel lines look for an area where they curve. I have seen the plastic lines kink at a curve when hot and when they cool they pop back to normal shape. Oh yes I so remember that truck.It took us months to find it.
UPDATE: So I got the shop to swap out the entire pump. They took the old one off and saw some scoring and a few other issues on it. Put in a new pump and ran it on the dyno...up and down for 45 mins and it didn't throw a code or de-rate.
The 157 code is still showing on my Nav screen...but I'm not sure if it's still an old code that wasn't reset. I'll hook up my computer and delete inactive codes and then I'll know if it shows up again.
Let us know how you made out once you clear those codes. I'd like to know what was scoring and the other "issues".
The good news is it appears to be repaired.
@@ENGINESHOPJOE so it worked to get rid of the low fuel rail pressure problem....but then I was getting an over fueling code (4727) and would cause the truck to idle rough and lope. Took it back and after some testing....they changed out a banjo bolt that has a check valve or needle valve in it that returns fuel to tank. Somewhere towards the back side of the engine is what I was told. Ive got the truck back to work for the last couple days and everything seems to be working now. 🤞
I have the old pump in my shop. I had put on a new actuator before so figured I'd keep it as the core was the price of the actuator. I haven't looked at the pump yet to see where the problem was.
Joe, does an active 559 code on isx12 (2014 model) cause it to fire right up, run 30 seconds, and die on its own time after time? Exactly 30 seconds it will die no matter how many times i start it. And it always fires right up runs 30 seconds and dies. It also runs fine while running. Is my 559 shutting ot down or something else? No other codes present.
30 seconds is how long the electric priming lift pump runs and sends about 15 psi to the on engine fuel filter.
It shuts off after 30 seconds.
put a 250 -500 psi gauge on the on engine filter pressure taps and see what the pressure is after 30 seconds.
Sounds like it is running out of fuel when it has to suck the fuel with the gear pump.
@ENGINESHOPJOE you're telling me the transfer pump is designed to stop pumping when the engine starts running and the gear pump takes over from there? I was not aware of that. When the engine is running you can't hear it and I thought it continually ran. But you're saying it does not?
On the ISX 11.9, 12,15 the electric lift pump is solely for priming before start up. It will run between 30 seconds to 120 seconds depending on engine model and year, ecm calibration and revision. The engines runs with a positive pressure gear pump much like a hydraulic pump. Early on they only ran 30 seconds. Then they extended that to up to 2 minutes because fuel system air leaks (worn shaft seals etc) allowed all the fuel to drain back to the tank. So the electric pump would prime the system. If you start the engien and it starts right up the lift pump still runs until the ecm shuts it off after a maximum of 2 minutes. FC 559 means the engine can not make the required common rail fuel pressure it needs. When 559 faults occur the engine might stall or it might keep running. That is because 559 is triggered when the fuel system is consistantly at least below about 350 psi below commanded fuel pressure. So if the system wants 12000 psi but can only make 11350 it will run fine but have the check engine light on and 559 active.
But if it commands 12000 and it drops to 3000 it will stall. Both of the above scenarios drive FC559. You also have to have continual low measured fuel pressure for over 15 or 30 seconds for that fault to even log. I gave two time stamps because they changed it in calibration updates. @@EugeneVincentOutdoors
@ENGINESHOPJOE the engine was oversped and broke the drive gear. Like you said, when transfer pump quit its run time, it shut down because the gear pump failed. My position was I did not know the run time for the pump. It's not clear cut.